Background: The prevalence of overweight and obesity are well known risk factors of atherosclerotic cardiovascular disease (ASCVD). We aimed to examine the association between body mass index (BMI) and ASCVD over a 23-year follow-up in young adults. We also qualified how much of the effects of obesity on ASCVD were mediated through blood pressure, cholesterol, and glucose.

Methods: Data are from the Korean Life Course Health Study, a cohort study of 226,955 Korean young adults aged 20–39. At baseline, the participants undertook routine health assessments where their BMI was measured in 1992–1994; and the metabolic mediators including systolic blood pressure (SBP), fasting serum glucose (FSG), and total cholesterol (TC) were re-measured in 2002–2004. The main outcomes of the study include incident events of ischemic heart disease (IHD), stroke, and ASCVD between 2005 and 2015. Cox proportional model was used to calculate adjusted hazard ratios (HRs) for ASCVD.

Results: In both men and women, the direct effect of BMI on ASCVD was greater than the indirect effect. The percentage of excess HR of BMI mediated by all of the metabolic mediators, including SBP, FSG, and TC, was 45.7% for stroke and 18.7% for IHD in men and 27.5% for stroke and 17.6% for IHD in women.

Conclusion: High BMI in young adults increases the risk of metabolic mediators in their middle age, and metabolic mediators explain the adverse effects of high BMI on stroke risk than IHD risk.

Background: Japan has witnessed an unusual increase in the number of suicides among women during the coronavirus disease 2019 pandemic. An analysis is required to identify the influencing factors during the pandemic and develop new measures for preventing suicides.

Methods: Data on the number of monthly suicides were collected from the National Police Agency of Japan. The expected number of suicides among women during the pandemic was estimated using a time-series model based on pre-pandemic data, considering year-to-year trends. The observed-to-expected (O/E) ratio of suicides was estimated from March 2020 to October 2021 using job status, suicide motive, and age.

Results: The number of suicides among women in Japan increased beyond the expected number until October 2021. The O/E ratio based on job status, suicide motive, and age (except self-employed, unknown job status, and women aged ≥80 years) was significantly above 1.0 from March–December 2020, and the increase in suicides continued in almost all categories in 2021.

Conclusion: Although several reasons were reported for increased suicides among women in Japan during the pandemic (eg, economic downturn, financial instability, and loneliness), suicides increased irrespective of job status, suicide motive, or age. Comprehensive measures to prevent suicide might have been important during the pandemic, instead of limiting interventions to the reported specific population.

Background

Alcohol drinking behaviors change temporally and can lead to changes in related cancer risks; previous studies have been unable to identify the association between the two using a single-measurement approach. Thus, this study aimed to investigate the association of drinking trajectories with the cancer risk in Korean men.

Methods

A trajectory analysis using group-based trajectory modeling was performed on 2,839,332 men using data on alcohol drinking levels collected thrice during the Korean National Health Insurance Service’s general health screening program conducted between 2002 and 2007. Cox proportional hazards regression was performed to evaluate the associations between drinking trajectories and cancer incidence, after adjustments for age, income, body mass index, smoking status, physical activity, family history of cancer, and comorbidities.

Results

During 10.5 years of follow-up, 189,617 cancer cases were recorded. Six trajectories were determined: non-drinking, light, moderate, decreasing-heavy, increasing-heavy, and steady-heavy. Light-to-heavy alcohol consumption increased the risk for all cancers combined in a dose-dependent manner (adjusted hazards ratio, 95% confidence interval for trajectories = 1.03, 1.02-1.05; 1.06, 1.05-1.08; 1.19, 1.16-1.22; 1.23, 1.20-1.26; and 1.33, 1.29-1.38; respectively [p-trend <0.001]). Light-to-heavy alcohol consumption was linked to lip, oral cavity, pharyngeal, esophageal, colorectal, laryngeal, stomach, and gallbladder and biliary tract cancer risks, while heavy alcohol consumption was associated with hepatic, pancreatic, and lung cancer risks. An inverse association was observed for thyroid cancer. The cancer risks were lower for decreasing-heavy drinkers, compared to steady-heavy drinkers.

Conclusion

No safe drinking limits were identified for cancer risks; reduction in heavy intake had protective effects.

Background: In 2016, two consecutive moderate magnitude earthquakes occurred in Ulsan, South Korea. Therefore, we aimed to investigate the impact of earthquakes on the mental health of residents in Ulsan.

Method: We used data from the 2015–2017 Korean Health Insurance Review & Assessment Service National Patient Sample. We conducted an interrupted time series analysis using location-based controls. Changes in the number of antidepressants, benzodiazepines, and zolpidem prescriptions in Ulsan were compared to controls. Overall changes in weekly prescriptions one year after the first earthquake, compared to a non-earthquake scenario, were estimated.

Results: In antidepressant prescriptions, the increase in trend after an earthquake was significantly higher than controls. However, the changes in benzodiazepines and zolpidem were not significant. Overall, the impact of the earthquake on weekly antidepressant prescriptions at one year was estimated as a 1.32 (95% CI: 1.18 - 1.56) rate ratio compared to the non-earthquake scenario. This corresponded to a 1,989.7 (95% CI: 1,202.1 to 3,063.0) increase in the number of prescriptions. Among subgroups, the increase was highest among males aged 20–39 years.

Conclusion: The moderate earthquake in Ulsan was associated with an increase in antidepressant prescriptions. The increase in the male group aged 20–39 was the highest. The impact may vary according to the context of the population.

Background: Reports of mortality-associated risk factors in patients with coronavirus disease (COVID-19) are limited.

Methods: We evaluated the clinical features that were associated with mortality among patients who died during hospitalization (N=158) and those who were alive at discharge (N=2,736) from the large-scale, multicenter, retrospective, observational cohort CLOT-COVID study enrolled consecutively hospitalized COVID-19 patients from 16 centers in Japan from April to September 2021. Data from 2,894 hospitalized COVID-19 participants of the CLOT-COVID study were analyzed in this study.

Results: Patients who died were older (71.1 years versus 51.6 years, P<0.001), had higher median D-dimer values on admission (1.7 μg/mL versus 0.8 μg/mL, P<0.001), and had more comorbidities. On admission, the patients who died had more severe COVID-19 than did those who survived (mild: 16% versus 63%, moderate: 47% versus 31%, and severe: 37% versus 6.2%, P<0.001). In patients who died, the incidence of thrombosis and major bleeding during hospitalization was significantly higher than that in those who survived (thrombosis: 8.2% vs. 1.5%, P<0.001; major bleeding: 12.7% vs. 1.4%, P<0.001). Multivariable logistic regression analysis revealed that age >70 years, high D-dimer values on admission, heart disease, active cancer, higher COVID-19 severity on admission, and development of major bleeding during hospitalization were independently associated with a higher mortality risk. Conclusions: This large-scale observational study in Japan identified several independent risk factors for mortality in hospitalized patients with COVID-19 that could facilitate appropriate risk stratification of patients with COVID-19.

Background: Although cigarette smoking is an established risk factor for bladder cancer, assessment of smoking impact on bladder cancer in Asian populations has been hindered by few cohort studies conducted in Asian populations. We therefore investigated the risk of bladder cancer associated with smoking status, cumulative smoking intensity and smoking cessation in Japan.

Methods: We analyzed data for 157,295 men and 183,202 women in ten population-based cohort studies in Japan. The risk associated with smoking behaviors was estimated using Cox regression models within each study, and pooled hazard ratios (HR) and their 95% confidence intervals (CI) for the incidence of bladder cancer were calculated.

Results: During 4,729,073 person-years of follow up, 936 men and 325 women developed bladder cancer. In men, former smokers (HR 1.47; 95% CI, 1.18-1.82) and current smokers (HR 1.96; 95% CI, 1.62-2.38) had higher risk than never smokers. In women, current smokers had higher risk than never smokers (HR 2.35; 95% CI, 1.67-3.32). HRs in men linearly increased with increasing pack-years. Risk decreased with increasing years of smoking cessation in men with a significant dose-response trend. Former smokers with a duration of more than 10 years after smoking cessation had no significantly increased risk compared with never smokers (HR 1.26; 95% CI, 0.97-1.63).

Conclusions: Data from a pooled analysis of ten population-based cohort studies in Japan clearly show an association between cigarette smoking and bladder cancer risk. The risk of smokers may approximate that of never smokers following cessation for many years.

Background: The impact of meeting leisure time physical activity (LTPA) recommendations and household physical activity (HPA) on all-cause mortality in the Taiwanese population is unclear. We aimed to investigate the relationship between sufficient LTPA and all-cause mortality in middle-aged and older Taiwanese adults and the role of HPA in those with insufficient LTPA.

Methods: This nationwide prospective cohort study included 4,960 participants aged ≥50 years from the Taiwan Longitudinal Study in Aging (TLSA) survey. Physical activity patterns were assessed in 2003 and then followed up until 2015 for mortality through the National Death Registration Record. Cox proportional hazards regression was conducted to evaluate hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality.

Results: Of the 4,960 participants, 1712 died of all-cause mortality. Compared to those who had insufficient LTPA, participants who engaged in sufficient LTPA showed a significantly lower risk of all-cause mortality (HR=0.84, 95% CI, 0.73-0.97). For those with insufficient LTPA, HPA also had a significantly reduced risk of all-cause mortality (HR=0.85, 95% CI, 0.75-0.96) among general population. Similar associations were observed in subsequent sensitivity analyses. The subgroup analysis showed that the relationship between HPA and reduced mortality risk was only found in the women with insufficient LTPA group.

Conclusion: This study confirmed that sufficient LTPA is associated with a lower risk of all-cause mortality. If sufficient LTPA cannot be performed, additional HPA is related to lower mortality.

Background: Serial weight decrease can be a prognostic predictor in chronic hemodialysis (HD) patients. We investigated the impact of long-term post-HD body weight (BW) changes on all-cause mortality among HD patients.

Methods: This longitudinal cohort study and post-hoc analysis evaluated participants of a previous randomized controlled trial conducted between 2006 and 2011 who were followed up until 2018. Weight change slopes were generated with repeated measurements every 6 months during the trial for patients having ≥5 BW measurements. Participants were categorized into four groups based on quartiles of weight change slopes; the median weight changes per 6 months were −1.02 kg, −0.25 kg, +0.26 kg, and +0.86 kg for first, second, third, and fourth quartile, respectively. Cox proportional hazard regression was used to evaluate differences in subsequent survival among the four groups. BW trajectories were plotted with a backward time-scale and multilevel regression analysis to visualize the difference in BW trajectories between survivors and non-survivors.

Results: Among the 461 patients, 404 were evaluated, and 168 (41.6%) died within a median follow-up period of 10.2 years. The Cox proportional hazard regression adjusted for covariates and baseline BW showed that a higher rate of weight loss was associated with higher mortality. The hazard ratios were 2.02 (95% confidence interval [CI], 1.28–3.20), 1.77 (95% CI, 1.10–2.85), 1.00 (reference), and 1.11 (95% CI, 0.67–1.83) for the first, second, third (reference), and fourth quartiles, respectively. BW trajectories revealed a significant decrease in BW in non-survivors.

Conclusion: Weight loss elucidated via serial BW measurements every 6 months is significantly associated with higher mortality among HD patients.

Background: New tobacco products, particularly heated tobacco products (HTPs), have been introduced across several international markets as alternatives to combustible products, such as cigarettes. However, there are limited studies on physicians’ perceptions of HTPs. This study analyzes the awareness of HTPs among physicians and assesses their concerns and attitudes toward patients using HTPs.

Methods: A self-administered questionnaire was sent to a sample of 7,500 member physicians (6,000 male and 1,500 female) from the Japan Medical Association (JMA). The smoking status of physicians was categorized as never smokers, ever HTP smokers, current HTP smokers, and ever and current smokers of other products. Physicians’ awareness and attitudes toward patients using HTPs were analyzed using descriptive statistics. The correlation between the outcomes was examined using logistic regression models, whereas physicians’ concerns about HTPs were analyzed using descriptive statistics.

Results: Data were obtained from 5,492 physicians (21.9% women; aged 60.4; standard deviation, 12.1 years) with a response rate of 74.6%. Overall, 76.7% of the physicians had awareness of HTP, and about half of whom asked patients about using HTPs. Physicians who took longer to discuss cessation were more likely to discourage patient use. Smoking status was associated with discouraging HTP use in patients. Physicians who had experience with HTP use were primarily concerned about the products’ long-term safety and less about product regulation.

Conclusion: Japanese physicians do not have sufficient information and knowledge about HTPs. Therefore, evidence-based guidelines are required to support physicians in advising patients against HTP use.

Background: In case-cohort studies with binary outcomes, ordinary logistic regression analyses have been widely used because of their computational simplicity. However, the resultant odds ratio estimates cannot be interpreted as relative risk measures unless the event rate is low. The risk ratio and risk difference are more favorable outcome measures that are directly interpreted as effect measures without the rare disease assumption.

Methods: We provide pseudo-Poisson and pseudo-normal linear regression methods for estimating risk ratios and risk differences in analyses of case-cohort studies. These multivariate regression models are fitted by weighting the inverses of sampling probabilities. Also, the precisions of the risk ratio and risk difference estimators can be improved using auxiliary variable information, specifically by adapting the calibrated or estimated weights, which are readily measured on all samples from the whole cohort. Finally, we provide computational code in R (R Foundation for Statistical Computing, Vienna, Austria) that can easily perform these methods.

Results: Through numerical analyses of artificially simulated data and the National Wilms Tumor Study data, accurate risk ratio and risk difference estimates were obtained using the pseudo-Poisson and pseudo-normal linear regression methods. Also, using the auxiliary variable information from the whole cohort, precisions of these estimators were markedly improved.

Conclusion: The ordinary logistic regression analyses may provide uninterpretable effect measure estimates, and the risk ratio and risk difference estimation methods are effective alternative approaches for case-cohort studies. These methods are especially recommended under situations in which the event rate is not low.

Background: The Japan Coma Scale (JCS) is the most frequently adopted method for evaluating level of consciousness in Japan. However, no validated method for converting the JCS to Glasgow Coma Scale (GCS) exists. The aims of the present study were to develop and validate a method to convert the JCS to GCS.

Methods: This is a multicenter retrospective cohort study involving three emergency departments (EDs) in Japan. We included all adult patients who visited the ED between 2017 and 2020. The participating facilities were divided into two cohorts—one cohort to develop a table to convert the JCS to GCS (development cohort), and the other cohort to validate the conversion table (validation cohort). The conversion table of the JCS to GCS was developed based on the median values of the GCS. The outcome was the concordance rate between the JCS and GCS.

Results: We identified 8,194 eligible patients. The development cohort included 7,373 patients and the validation cohort included 821 patients. In the validation cohort, the absolute and relative concordance rates were 80.3% (95% confidence interval, 77.4–82.9%) and 93.2% (95% confidence interval, 91.2–94.8%), respectively.

Conclusions: This study developed and validated a novel method for converting the JCS to GCS. Assuming the offset by a single category between the JCS and GCS is acceptable, the concordance rate was over 90% in the general adult patient population visiting the ED. The conversion method may assist researchers to convert JCS into GCS, which is more commonly recognized among global audiences.

Background: Desired longevity represents how strongly people esteem possible extensions of their own lifetime. The association between desired longevity and mortality risk has been reported in only one prospective study, which examined a small sample of older participants. We aimed to examine the hypothesis that desired longevity at middle-age predicted long-term survival.

Methods: In the prospective cohort study, residents aged 40–64 years were asked how long they would like to live and asked to choose one from three options: longer than, as long as, or shorter than the life expectancy. We used Cox proportional hazards model to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause and cause-specific mortality according to the three groups for desired longevity, treating the “longer than” group as the reference. We conducted mediation analysis to investigate the mechanism for the association between desired longevity and mortality.

Results: We recruited 39,902 residents to the study. Risk of all-cause mortality was significantly higher in the “shorter than” group (HR 1.12; 95% CI, 1.04–1.21). The association was independent of sex, age, marital status, education, medical history, and health status. Regarding cause of death, mortality risk of cancer (HR 1.14; 95% CI, 1.00–1.29) and suicide (HR 2.15; 95% CI, 1.37–3.38) were also higher in the “shorter than” group. The unhealthy lifestyle mediated this association with all-cause mortality by 30.4%.

Conclusion: Shorter desired longevity was significantly associated with an increased risk of all-cause mortality, and mortality from cancer and suicide. Lifestyle behaviors particularly mediated this association.

Background: Little is known about the association between a plant-based diet and the risk of gallstone disease (GD), especially in developing counties. We tested the hypothesis that shifting dietary patterns would be related to the risk of GD, and that the Mediterranean diet (MED) adjusted for China would be beneficial for lowering risk of GD.

Methods: Data were extracted from the baseline survey of the China Multi-Ethnic Cohort study. An alternative Mediterranean diet (aMED) score was assessed based on a food frequency questionnaire, and three posteriori dietary patterns (the modern dietary pattern, the coarse grain dietary pattern, and the rice dietary pattern) were identified using factor analysis. Multivariable logistic regression models were developed to evaluate the association between dietary patterns and GD risks.

Results: A total of 89,544 participants were included. The prevalence of GD was 7.5%. Comparing the highest with lowest quintiles, aMED was associated with an increased risk of GD (OR 1.13; 95% CI, 1.04–1.24; P_trend = 0.003), whereas the rice dietary pattern was inversely related to GD risk (OR 0.79; 95% CI, 0.71–0.87; P_trend < 0.001). In stratified analysis, the rice dietary pattern had a stronger inverse association in the subgroups of females, older, urban, and overweight participants, and those with diabetes—factors associated with higher rates of GD in previous studies.

Conclusion: Higher adherence to the rice dietary pattern was associated with a lower risk of GD. For high-risk populations, making some shift to a traditional agricultural diet might help with primary prevention of GD.

Background: Prioritization for novel coronavirus disease 2019 (COVID-19)-related health policies usually considers age and certain other characteristics, but sex is rarely included, despite the higher risk of severe disease in men. The aim of this study was to compare the impact of sex and age on the severity of COVID-19 by estimating the age difference in years for which the risk for men versus women is the same.

Methods: We analyzed 23,414 Japanese COVID-19 inpatients aged 20–89 years (13,360 men and 10,054 women). We graded the severity of COVID-19 (0 to 5) according to the most intensive treatment required during hospitalization. The risk of grade 2/3/4/5 (non-invasive positive pressure ventilation/invasive mechanical ventilation/extracorporeal membrane oxygenation/death), grade 3/4/5, and separately grade 5 was analyzed using a multiple logistic regression model.

Results: The odds ratio (OR) of grades 2/3/4/5, 3/4/5 (primary outcome), and 5 for men relative to women was 2.76 (95% CI, 2.44–3.12), 2.78 (95% CI, 2.42–3.19), and 2.60 (95% CI, 2.23–3.03), respectively, after adjustment for age and date of admission. These risks for men were equivalent to those for women 14.1 (95% CI, 12.3–15.8), 11.2 (95% CI, 9.7–12.8), and 7.5 (95% CI, 6.3–8.7) years older, respectively.

Conclusion: The risks of worse COVID-19 prognosis (grades 3/4/5) in men were equivalent to those of women 11.2 years older. Reanalyzing data extracted from four previous studies also revealed a large impact of sex difference on the severity of COVID-19. We should pay more attention to sex differences to predict the risk of COVID-19 severity and to formulate public health policy accordingly.

Background

Little is known about the impacts of sleep duration and daytime napping on the risk of type 2 diabetes mellitus (T2DM).

Methods

In this study, 20,318 participants (7,597 men, 12,721 women) aged 40–79 years without a history of T2DM, stroke, coronary heart disease, or cancer at baseline (1988–1990), completed the baseline survey and the 5-year follow-up questionnaires, which included average sleep duration, napping habits, and self-reports of physician-diagnosed diabetes. The multivariable odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using a logistic regression model.

Results

During the 5-year follow-up, 531 new cases of T2DM (266 men and 265 women) were documented. Sleep duration ≥ 10 h was associated with higher risk of T2DM compared to sleep duration of 7 h (OR 1.99: 95%CI, 1.28–3.08). The excess risk was observed for both sexes and primarily found among the non-overweight; the multivariable ORs of sleeping ≥ 10 h compared to 7 h were 2.05 (1.26–3.35) for the non-overweight (BMI < 25 kg/m²) and 1.38 (0.49–3.83) for the overweight (BMI ≥ 25 kg/m²). The respective ORs of nappers vs non-nappers were 1.30 (1.03–1.63) and 0.92 (0.65–1.29). Among the non-overweight, nappers who slept ≥ 10 h had the highest risk of T2DM (OR 2.84: 95%CI, 1.57–5.14), non-nappers who slept ≥ 10 h (2.27: 1.27–4.06), and nappers who slept < 10 h (1.30: 1.03–1.64), compared with non-nappers who slept < 10 h.

Conclusions

Long sleep duration was associated with the risk of T2DM in both sexes, which was confined to the non-overweight.

Background: Whether sleep quality and duration-combination assessed from multiple domains are strongly associated with mortality risk in older adults remains unelucidated. We aimed to clarify these relationships.

Methods: We enrolled 7,668 older (age ≥65) Japanese adults in the Kyoto-Kameoka prospective cohort study who provided valid responses to the Pittsburgh Sleep Quality Index (PSQI) in a mail-in survey. Sleep quality and duration were classified into six groups using previously validated PSQI: short sleep duration (SSD: <360 min/day)/sleep disturbance (SD: ≥5.5 PSQI points), n=701; SSD/non-sleep disturbance (NSD: <5.5 PSQI points), n=100; optimal sleep duration (OSD: 360-480 min/day)/NSD, n=1863; OSD/SD, n=2113; long sleep duration (LSD: >480 min/day)/NSD, n=1972; LSD/SD, n=919. Mortality data were collected from February 15, 2012, to November 30, 2016. We evaluated the relationship between all-cause mortality risk and sleep quality and duration-combination using a multivariable Cox proportional hazards model that included baseline covariates.

Results: The median follow-up period was 4.75 years (34,826 person-years), with a total of 616 deaths. After adjusting for confounders, compared with other groups, SSD/SD and LSD/SD had the highest hazard ratio (HR) of mortality [SSD/SD: HR, 1.56 (95% confidence interval [CI]: 1.10-2.19); SSD/NSD: HR, 1.27 (95%CI: 0.47-3.48); OSD/NSD: reference; OSD/SD: HR, 1.20 (95%CI: 0.91-1.59); LSD/NSD: HR, 1.35 (95%CI: 1.03-1.77); LSD/SD: HR, 1.83 (95%CI: 1.37-2.45)]. However, mortality risk was not associated with the interaction between sleep quality and duration.

Conclusions: Older adults with sleep disturbances involving SSD and LSD have a strong positive association with mortality risk, suggesting an additive effect between sleep quality and duration.

Background: Pseudohypoparathyroidism (PHP) and nonsurgical hypoparathyroidism (NS-HypoPT) are rare diseases with hypocalcemia, hyperphosphatemia, and high and low parathyroid hormone levels, respectively. In Japan, over 20 years have passed since the last survey on these diseases. We carried out a nationwide cross-sectional survey to estimate the prevalence of these diseases in 2018.

Methods: We conducted a nationwide mail-based survey targeting hospitals in 2018. From a total of 13,156 departments throughout Japan, including internal medicine, pediatrics, neurology, and psychiatry, 3501 (27%) departments were selected using a stratified random sampling method. We asked each included department to report the number of patients with PHP and NS-HypoPT in 2017.

Results: The overall survey response rate was 52.0% (1807 departments). The estimated number of patients with PHP and NS-HypoPT was 1484 (95% confidence interval [CI], 1143–1825) and 2304 (95% CI, 1189–3419), respectively; the prevalence per 100,000 population was 1.2 and 1.8, respectively.

Conclusion: In this study, we generated estimates of the national prevalence of PHP and NS-HypoPT in Japan during 2017, which were found to be higher than those previously reported.

Background: Since 2011, commercial truck drivers have been required to take alcohol breath tests at the beginning and end of their working hours due to their employers’ legal obligations. However, non-commercial truck drivers are not required to do so. We examined whether alcohol-related crashes had decreased after 2011 among commercial truck drivers.

Methods: Using police data, we conducted a joinpoint regression analysis to examine the trend in the proportion of alcohol-related crashes from 1995 to 2020 caused by commercial truck drivers (who were subjected to alcohol breath testing) and non-commercial truck drivers (who were not subjected to testing). The annual percentage change in this trend was also estimated.

Results: During the 26-year study period, truck drivers caused 1,846,321 at-fault crashes, and 0.4% of the crashes involved intoxicated driving. A significant decreasing trend in the proportion of alcohol-related crashes was identified among both commercial and non-commercial truck drivers in the 2000s, during which several legal amendments were made against drunk driving. The annual percentage change was –13.5% from 2001 to 2012 among commercial truck drivers, and –14.9% from 2001 to 2011 among non-commercial truck drivers. No decreasing trend was observed afterwards, despite the introduction of mandatory alcohol breath testing in 2011.

Conclusions: The effect of mandatory alcohol breath testing on reducing alcohol-related crashes among commercial truck drivers was not evident.

Background: Tobacco exposure during pregnancy is associated with several adverse outcomes in infants. We investigated the association between tobacco exposure during pregnancy (both active and second-hand) and various infections in infants up to 1 year.

Methods: This prospective cohort study used a fixed dataset (jecs-an-20180131) from the Japan Environment and Children’s Study of registered births in Japan during 2011–2014 that included 104,065 fetal records from enrolled pregnant women. Based on the participants’ responses to the questionnaire on smoking status, mothers were first divided into “never smoked,” “quit smoking,” and “current smoker” groups and then into “no second-hand smoking (SHS)” and “SHS” groups. Infectious diseases included central nervous system infection, otitis media (OM), upper respiratory tract infection (URTI), lower respiratory tract infection (LRTI), gastroenteritis (GI), and urinary tract infection. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated using logistic regression analysis and adjusted for maternal, socioeconomic, and postnatal confounding factors.

Results: Among the 73,205 newborns enrolled, multivariable analysis revealed that the aOR of LRTI and GI was 1.20 (95% CI, 1.07–1.33) and 1.18 (95% CI, 1.04–1.35), respectively, for the “current smoker with/without SHS” group compared with the “never smoked without SHS” group. “Quit smoking without SHS” was not associated with the risk of LRTI. SHS was associated with an increased risk of OM, URTI, LRTI, and GI, especially with LRTI and GI.

Conclusion: Exposure to tobacco smoke during pregnancy was associated with an increased risk of OM, URTI, LRTI, and GI in infants during their first year of life.

Background: Cold exposure induces lower urinary tract symptoms, including nocturia. Cold-induced detrusor overactivity can be alleviated by increasing skin temperature in rats. However, no study has shown an association between passive heating via hot-water bathing and nocturia among humans.

Methods: We included 1,051 Japanese community-dwelling older adults (mean age: 71.7 years) in this cross-sectional study from 2010 to 2014. The number of nocturnal voids was recorded in a self-administered urination diary. Nocturia was defined as ≥2 nocturnal voids. We evaluated bathing conditions in the participants’ houses.

Results: Hot-water bathing (n = 888) was associated with a lower prevalence of nocturia than no bathing (n = 163), independent of potential confounders, including age, sex, obesity, income, physical activity, diabetes, medication (diuretics, nondiuretic antihypertensives, and hypnotics), depressive symptoms, indoor/outdoor temperature, and day length (odds ratio [OR] 0.68; 95% confidence interval [CI], 0.48–0.97; P = 0.035). Compared with the quartile group with the longest bath-to-bed interval (range: 161–576 min), the second and third quartile groups (range: 61–100 and 101–160 min, respectively) were associated with a lower prevalence of nocturia, after adjusting for water temperature and bathing duration besides the same covariates (OR 0.60; 95% CI, 0.38–0.96; P = 0.031 and OR 0.59; 95% CI, 0.37–0.94; P = 0.025, respectively).

Conclusion: Hot-water bathing, particularly with a bath-to-bed interval of 61–160 min, was significantly associated with a lower prevalence of nocturia among older adults.

Background: Progress in reducing the global low birthweight (LBW) has been insufficient. Although the focus has been on preventing preterm birth, evidence regarding LBW in term births is limited. Despite its low preterm birth prevalence, Japan has a higher LBW proportion than other developed countries. This study aimed to examine the prevalence of LBW in term singleton births and its associated factors using a national database.

Methods: We retrospectively analyzed the data of neonates registered in the Japan Society of Obstetrics and Gynecology Successive Pregnancy Birth Registry System who were born 2013–2017. Exclusion criteria included stillbirths, delivery after 42 gestational weeks, and missing data. Logistic regression analyses were performed to investigate the maternal and perinatal factors associated with LBW in term singletons using the data of 715,414 singleton neonates.

Results: The overall prevalence of LBW was 18.3%, and 35.7% of LBWs originated from singleton term pregnancies. Multiple logistic regression analyses indicated that both modifiable and non-modifiable factors were independently associated with LBW in term neonates. The modifiable maternal factors included pre-pregnancy underweight, inadequate gestational weight gain, and smoking during pregnancy, while the non-modifiable factors included younger maternal age, nulliparity, hypertensive disorders of pregnancy, cesarean section delivery, female offspring, and congenital anomalies.

Conclusion: Using the Japanese pregnancy birth registry data, more than one-third of LBWs were found to originate from singleton term pregnancies. Both modifiable and non-modifiable factors were independently associated with LBW in term neonates. Prevention strategies on modifiable risk factor control will be effective in reducing LBW worldwide.

Background: The association between hobby engagement and risk of dementia reported from a short-term follow-up study for individuals aged ≥65 years may be susceptible to reverse causation. We examined the association between hobby engagement in age of 40–69 years and risk of dementia in a long-term follow-up study among Japanese, including individuals in mid-life, when the majority of individuals have normal cognitive function.

Methods: A total of 22,377 individuals aged 40–69 years completed a self-administered questionnaire in 1993–1994. The participants answered whether they had hobbies according to the three following responses: having no hobbies, having a hobby, and having many hobbies. Follow-up for incident disabling dementia was conducted with long-term care insurance data from 2006 to 2016.

Results: During a median of 11.0 years of follow-up, 3,095 participants developed disabling dementia. Adjusting for the demographic, behavioral, and psychosocial factors, the multivariable hazard ratios of incident disabling dementia compared with “having no hobbies” were 0.82 (95% confidence interval [CI], 0.75–0.89) for “having a hobby” and 0.78 (95% CI, 0.67–0.91) for “having many hobbies”. The inverse association was similarly observed in both middle (40–64 years) and older ages (65–69 years). For disabling dementia subtypes, hobby engagement was inversely associated with the risk of dementia without a history of stroke (probably non-vascular type dementia), but not with that of post-stroke dementia (probably vascular type dementia).

Conclusion: Hobby engagement in both mid-life and late life was associated with a lower risk of disabling dementia without a history of stroke.

Background Hypertension is one of the most common chronic diseases, and dietary factors play an important role in hypertension. We examined the interaction of dietary sodium-to-potassium (Na/K) ratio and dinner energy ratio on hypertension. Methods We conducted this study using data from cross-section, the National Survey for Nutrition and Adult Chronic Disease in 2015 in Inner Mongolia (China). Dietary data were collected by using 24-hour diet records with food weights across three consecutive days. Logistic regression was used to determine the interaction of dinner energy ratio and dietary Na/K ratio on hypertension. Results A total of 1,861 participants were included in this study, of those 914 individuals were hypertensive (49.1%). Dinner energy ratio and high dietary Na/K ratio were independently related to high prevalence of hypertension. A formal test showed that dinner energy ratio interacted significantly with dietary Na/K ratio on hypertension (P<0.001), with the adjusted OR (95%CI) of 1.119 (1.040-1.203). Participants whose dinner energy ratio greater than 39.1% and dietary Na/K ratio within 3.625 and 6.053 had the highest odds ratio of hypertension prevalence, with the adjusted OR (95%CI) of 2.984 (1.758-5.066), comparing with participants those dinner energy ratio within 30.2% and 39.1%, and dietary Na/K ratio less than 2.348. Conclusions Our study highlighted the interactive effect of dinner energy ratio and dietary Na/K ratio on hypertension among adults in Inner Mongolia. We advocated a balanced diet (dinner energy ratio not small or large) and a low dietary Na/K ratio for reducing the prevalence of hypertension.

Background: Recent literature suggest the effect of maternal smoking on risk of hypertensive disorders in pregnancy (HDP) and preeclampsia may differ by ethnicity, however studies on Asians are limited.

Methods: We investigated the association between maternal smoking and HDP and preeclampsia, by using a common analysis protocol to analyze the association in six birth cohorts participating in a Japanese consortium of birth cohorts (JBiCC). Results were compared with published results from cohorts not included in this consortium, and where possible produced a meta-analysis including these studies.

Results: Meta-analysis of four cohort studies including 28,219 participants produced an odds ratio (OR) of 1.24 (95% confidence interval (CI) 0.88-1.87) for effect of smoking beyond early pregnancy compared to women who did not smoke during pregnancy. These results combined with those from the Japan Environment and Children’s Study (JECS) yielded an OR of 1.19 (95%CI 1.00-1.43, p=0.056). Meta-analysis results for categories of smoking volume were insignificant, but when combined with JECS yielded an OR of 0.86 (95%CI 0.65-1.12) for smoking 1-4 cigarettes, 1.25 (95%CI 0.98-1.60) for smoking 5-9 cigarettes, and 1.27 (95%CI 1.04-1.54) for smoking 10 or more cigarettes per day. All effects were insignificant for preeclampsia.

Conclusion: Our results suggest the protective effect of smoking longer, smoking more on HDP and preeclampsia repeatedly observed among Europeans and North Americans likely do not hold for the Japanese.

Background: Limited reports from human prospective studies investigated the possible role of vitamin K in the development of lung cancer although vitamin K’s anticarcinogenic activities were verified from several in vitro and in vivo studies.

Objectives: We investigated the associations between total vitamin K intake from food and the development of lung cancer based on this large prospective cohort study.

Methods: A validated food frequency questionnaire was used to examine vitamin K intake among 42,166 (16,341 men and 25,825 women) at the Japan Collaborative Cohort Study's baseline (1988-1990). Hazard ratios (HRs) and 95% confidence intervals (CIs) of incident lung cancer were calculated using the Cox proportional hazard regression method based on vitamin K consumption quartiles.

Results: 430 cases (308 males and 122 women) of lung cancer were documented during a total of 564,127 person-years of follow-up (median follow-up= 14.6 years). Vitamin K consumption was shown to be inversely related to lung cancer risk; the multivariable HR (95 % CI) for the highest vs. lowest quartiles was 0.67 (0.46-0.96; p for trend = 0.010). This relationship appears to be stronger in males [0.62 (0.40-0.96); p for trend=0.016] than in females [0.82 (0.42-1.61); p for trend=0.39] (p for interaction=0.012), and in ever smokers [0.57 (0.36-0.91); p for trend=0.006] than in never smokers [0.79 (0.40-1.55); p for trend=0.37] (p for interaction= 0.30). The individuals' age, BMI, or alcohol consumption status had no effect on the observed connection.

Conclusion: Vitamin K consumption reduces the risk of lung cancer. More research is needed to clarify the molecular processes behind this connection.

Background: It has not been determined whether mentally active sedentary behavior (MASB) and passive sedentary behavior (PSB) differentially affect cognitive function and whether these associations differ according to physical activity (PA) level. We examined the comparative impacts of MASB and PSB on dementia onset and aimed to understand whether the associations differed by PA level.

Methods: We conducted a 5-year longitudinal study involving all community-dwelling older adults in a rural area in Japan (n = 5,323). Dementia onset was examined using long-term care insurance data. PA was evaluated using the International Physical Activity Questionnaire and categorized as low (<2.5 metabolic equivalent of task [MET]-h/week), moderate (2.5–16.0 MET-h/week), or high (≥16.0 MET-h/week). We also assessed PSB (TV-watching time; <1 h/day, 1–3 h/day, ≥3 h/day) and MASB (Book-reading time; <10 min/day, 10–30 min/day, ≥30 min/day). To examine the associations of MASB and PSB with dementia onset, we performed the Fine-Gray models accounting for competing risk of death.

Results: During the follow-up period, 606 (11.4%) participants developed dementia. MASB was independently associated with a lower risk of dementia; the magnitude of the impact was significant at higher PA levels. There was no association between PSB and developing dementia across all PA levels. Furthermore, dementia risk for individuals with high PA levels and moderate or high MASB levels was approximately 60% lower than those with low PA levels and low MASB.

Conclusion: Providing interventions to promote MASB, which reduces dementia risk, and PA, which increases MASB’s effect on dementia incidence, can be beneficial in delaying or preventing dementia onset.

Background: Previous studies have shown that socioeconomic factors are associated with cancer incidence and stage at diagnosis; however, relevant findings in Japan are limited. We examined the association between socioeconomic status and cancer incidence, stage at diagnosis, and detection status by screening, as assessed by the areal deprivation index (ADI), using population-based cancer registry data.

Methods: A total of 79,816 cases including stomach, colorectal, lung, female breast, and cervical cancer diagnosed in Miyagi Prefecture between 2005 and 2010 were analyzed. After calculating the ADI at the place of residence in each case, we examined the association between quintiles of ADI and age-adjusted incidence rates of all stages and advanced stages by sex and site using Poisson regression analysis. The association between the ADI and the proportion of screen-detected cancers was also examined using logistic regression analysis.

Results: The age-adjusted incidence rates of all sites and lung cancer in men and lung cancer and cervical cancer in women tended to increase significantly in areas with a higher ADI. The age-adjusted incidence rates of advanced-stage cancers were significantly higher for all sites and lung cancer in both sexes, and stomach and colorectal cancer in men. The proportion of screen-detected cancer tended to be significantly lower in areas with a higher ADI for stomach and colorectal cancer in men.

Conclusion: Our results indicate that socioeconomic disparities may affect cancer incidence and early diagnosis in Japan. These results suggest the importance of cancer control measures targeting people with low socioeconomic status in Japan.

Background: The counterfactual definition of confounding is often explained in the context of exchangeability between the exposed and unexposed groups. One recent approach is to examine whether the measures of association (eg, associational risk difference) are exchangeable when exposure status is flipped in the population of interest. We discuss the meaning and utility of this approach, showing their relationships with the concept of confounding in the counterfactual framework.

Methods: Three hypothetical cohort studies are used, in which the target population is the total population. After providing an overview of the notions of confounding in distribution and in measure, we discuss the approach from the perspective of exchangeability of measures of association (eg, factual associational risk difference vs counterfactual associational risk difference).

Results: In general, if the measures of association are non-exchangeable when exposure status is flipped, confounding in distribution is always present, although confounding in measure may or may not be present. Even if the measures of association are exchangeable when exposure status is flipped, there could be confounding both in distribution and in measure. When we use risk difference or risk ratio as a measure of interest and the exposure prevalence in the population is 0.5, testing the exchangeability of measures of association is equivalent to testing the absence of confounding in the corresponding measures.

Conclusion: The approach based on exchangeability of measures of association essentially does not provide a definition of confounding in the counterfactual framework. Subtly differing notions of confounding should be distinguished carefully.

Background: Having siblings may foster sociality; however, little is known about whether sibling number determines social capital, the resources obtained through social networks. We examined the association between sibling number and social capital among Japanese parents rearing schoolchildren.

Methods: We used cross-sectional data from the 2018 and 2019 Adachi Child Health Impact of Living Difficulty (A-CHILD) study, targeting all primary and junior high school students and their parents in Adachi, Tokyo, Japan (n = 8,082). Individual-level social capital was evaluated by assessing caregivers’ social cohesion, social support, and group affiliation. All analyses were adjusted for age and sex.

Results: An inverse U-shaped association was found between sibling number and social capital. Adults who grew up with one or two, but not three or more siblings had greater social support (coefficient = 0.23; 95% confidence interval [CI], 0.06–0.40 and coefficient = 0.46; 95% CI, 0.29–0.64, respectively) than those who grew up as an only child, after covariate adjustment. Adults who grew up with two or three, but not one or four or more siblings had greater group affiliation (coefficient = 0.09; 95% CI, 0.03–0.16 and coefficient = 0.09; 95% CI, 0.01–0.18, respectively) than those who grew up as an only child, after covariate adjustment. Sibling number was not associated with social cohesion.

Conclusion: Growing up with one to three siblings was associated with higher social capital in adulthood than being an only child. Having siblings may provide an opportunity to foster social capital.

Background: The Longevity Improvement & Fair Evidence (LIFE) Study, which was launched in 2019, is a multi-region community-based database project that aims to generate evidence toward extending healthy life expectancy and reducing health disparities in Japan. Herein, we describe the LIFE Study’s design and baseline participant profile.

Methods: Municipalities participating in the LIFE Study provide data from government-administered health insurance enrollees and public assistance recipients. These participants cover all disease types and age groups. Centered on healthcare claims data, the project also collects long-term care claims data, health checkup data, vaccination records, residence-related information, and income-related information. The different data types are converted into a common data model containing five modules (health care, long-term care, health checkup, socioeconomic status, and health services). We calculated the descriptive statistics of participants at baseline in 2018.

Results: The LIFE Study currently stores data from 1,420,437 residents of 18 municipalities. The health care module contains 1,280,756 participants (mean age: 65.2 years), the long-term care module contains 189,069 participants (mean age: 84.3 years), and the health checkup module contains 274,375 participants (mean age: 69.0 years). Although coverage and follow-up rates were lower among younger persons, the health care module includes 74,151 children (0–19 years), 273,157 working-age adults (20–59 years), and 933,448 older persons (≥60 years).

Conclusion: The LIFE Study provides data from over 1 million participants and can facilitate a wide variety of life-course research and cohort studies. This project is expected to be a useful platform for generating real-world evidence from Japan.

Background: Total work-family conflicts (TWFCs) could associate with mental health, and having ikigai (a purpose of life) may mediate this association.

Methods: In a cross-cultural study of 4,792 Japanese Aichi Workers’ Cohort study participants and 3,109 Egyptian civil workers, the Midlife Development in the United States (MIDUS) questionnaire measured TWFCs and the Center for Epidemiological Studies Depression (CES-D) 11-item scale measured depression. We used logistic regression models to estimate odds ratios (ORs) of having depression and a high-ikigai across levels of TWFCs (low, moderate, and high), and the PROCESS macro of Hayes to test the mediation effect.

Results: The prevalence of high TWFCs, depression, and having a high ikigai were 17.9%, 39.4%, and 70.1% in Japanese women, 10.5%, 26.8%, and 70.1% in Japanese men, 23.7%, 58.2%, and 24.7% in Egyptian women, and 19.1%, 38.9%, and 36.9% in Egyptian men, respectively. Compared with participants with low TWFCs, the multivariable ORs of depression in Japanese women and men with high TWFCs were 4.11 (95% confidence interval [CI], 2.99–5.65) and 5.42 (95% CI, 4.18–7.02), and those in Egyptian women and men were 4.43 (95% CI, 3.30–5.95) and 4.79 (95% CI, 3.53–6.48), respectively. The respective ORs of having a high-ikigai were 0.46 (95% CI, 0.33–0.64) and 0.40 (95% CI, 0.31–0.52) in Japanese women and men and were 0.34 (95% CI, 0.24–0.48) and 0.28 (95% CI, 0.20–0.39) in Egyptian women and men. No interaction between TWFCs and country was observed for the associations with depression or ikigai. Ikigai mediated (up to 18%) the associations between the TWFCs and depression, especially in Egyptian civil workers.

Conclusion: TWFCs were associated with depression, and having low ikigai mediated these associations in Japanese and Egyptian civil workers.

Background: Recent innovations in information and communication technology have made it possible to assess diet using web-based methods; however, their applicability in the general population remains unclear. Hence, we aimed to examine the applicability of a web-based 24-hour dietary recall (24HR) tool to large-scale epidemiological studies by determining the sampling rate and characteristics of randomly selected participants from a Japanese cohort study.

Methods: In total, 5,013 individuals were recruited from a cohort of 21,537 individuals, and 975 agreed to participate in this study. The participants selected either self-administered web-based dietary 24HR (self-administered 24HR) or interviewer-administered telephone-based 24HR (interviewer-administered 24HR) as the method for the dietary assessment and answered questions regarding the acceptability of the system.

Results: The response rate of the 975 participants was 19.4%, corresponding to approximately 4.5% of the total study sample. About half of them chose the self-administered 24HR (46.9%). The median time required for the self-administered and interviewer-administered 24HR was 25 and 27 minutes, respectively. In the self-administered 24HR, older people, regardless of sex, tended to require a longer time, and approximately 60% of the participants rated the ease of use of the system as “somewhat difficult” or “difficult.”

Conclusion: Characteristics of the participants in this study were not systemically different from those of the entire study sample. Improvements in the approach to entering cooking details and the dish name selection may be necessary for better acceptability in order to be accepted as a self-administered dietary recall tool.

Background: Identifying which exposures cause disease and quantifying their impacts is essential in promoting and monitoring public health. When multiple exposures are involved, measuring individual contributions becomes challenging.

Methods: The authors propose a disease attribution method based on aggregate data or summary statistics of individual-level data, possibly from multiple data sources.

Results: Using the proposed method, the burden of disease is apportioned to the independent and interaction effects of each of its major risk factors and all the other factors as a whole. This scheme guarantees that 100% is the total share of the burden.

Conclusion: The calculation is simple and straightforward; therefore, it is recommended for use in studies on disease burden.

Background: No studies have examined the associations between adult height and ischemic stroke subtypes.

Methods: We conducted a population-based case-control study that included 2,451 thrombotic and 687 embolic stroke cases, as well as 1,623 intracerebral and 768 subarachnoid hemorrhage cases without history of stroke aged 40–79 years, and the same number of sex- and age-matched controls. Cases and controls were grouped according to the quintile cut-off values of height in controls, and the third quintile, which was approximately the average height group, was used as the reference group. Height divided by one standard deviation of height in controls was also examined as a continuous variable. The analyses were carried out separately for participants aged 40–59 years and 60–79 years.

Results: In both younger and older men, height was linearly inversely associated with total and thrombotic strokes, and the shortest quintile compared to the reference group was associated with increased risks of these strokes. Although height was linearly inversely associated with embolic stroke and intracerebral hemorrhage in younger men, the shortest quintile did not show increased risks of these strokes. Height did not seem to be associated with total stroke and any stroke subtypes in younger women. In contrast, the tallest quintile was significantly associated with increased risks of total stroke and intracerebral hemorrhage, and height tended to be positively associated with these strokes in older women.

Conclusion: We reported the associations between adult height and ischemic stroke subtypes for the first time, which differed according to sex and age group.

Background: Stress coping strategies are related to health outcomes. However, there is no clear evidence for sex differences between stress-coping strategies and mortality. We investigated the relationship between all-cause mortality and stress-coping strategies, focusing on sex differences among Japanese adults.

Methods: A total of 79,580 individuals aged 35–69 years participated in the Japan Multi-Institutional Collaborative Cohort Study between 2004 and 2014 and were followed up for mortality. The frequency of use of the five coping strategies was assessed using a questionnaire. Sex-specific, multivariable-adjusted hazard ratios (HRs) for using each coping strategy (“sometimes,” and “often/very often” use versus “very few” use) were computed for all-cause mortality. Furthermore, relationships were analyzed in specific follow-up periods when the proportion assumption was violated.

Results: During the follow-up (median: 8.5 years), 1,861 mortalities were recorded. In women, three coping strategies were related to lower total mortality. The HRs for “sometimes” were 0.81 (95% confidence interval [CI], 0.67–0.97) for emotional expression, 0.79 (95% CI, 0.66–0.95) for emotional support-seeking, and 0.80 (95% CI, 0.66–0.98) for disengagement. Men who “sometimes” used emotional expression and sometimes or often used problem-solving and positive reappraisal had a 15–41% lower HRs for all-cause mortality. However, those relationships were dependent on the follow-up period. There was evidence that sex modified the relationships between emotional support-seeking and all-cause mortality (P for interaction = 0.03).

Conclusion: In a large Japanese sample, selected coping strategies were associated with all-cause mortality. The relationship of emotional support-seeking was different between men and women.

Background: The EU LifeCycle Project was launched in 2017 to combine, harmonize, and analyze data from more than 250,000 participants across Europe and Australia, involving cohorts participating in the EU-funded LifeCycle Project. The purpose of this cohort description is to provide a detailed overview of the major measures within mental health domains that are available in 17 European and Australian cohorts participating in the LifeCycle Project.

Methods: Data on cognitive, behavioral, and psychological development has been collected on participants from birth until adulthood through questionnaire and medical data. We developed an inventory of the available data by mapping individual instruments, domain types, and age groups, providing the basis for statistical harmonization across mental health measures.

Results: The mental health data in LifeCycle contain longitudinal and cross-sectional data from birth throughout the life course, covering domains across a wide range of behavioral and psychopathology indicators and outcomes, including executive function, depression, ADHD, and cognition. These data span a unique combination of qualitative data collected through behavioral/cognitive/mental health questionnaires and examination, as well as data from biological samples and indices in the form of imaging (MRI, fetal ultrasound) and DNA methylation data. Harmonized variables on a subset of mental health domains have been developed, providing statistical equivalence of measures required for longitudinal meta-analyses across instruments and cohorts.

Conclusion: Mental health data harmonized through the LifeCycle project can be used to study life-course trajectories and exposure-outcome models that examine early life risk factors for mental illness and develop predictive markers for later-life disease.

Background: White rice is a staple food for Japanese, a population at high risk for colorectal cancer (CRC). We investigated the association between white rice intake and CRC among Japanese Americans in the Multiethnic Cohort (MEC) study.

Methods: The MEC study is a prospective study established in Hawaii and California in 1993–1996. Usual dietary intake was assessed using a validated quantitative food frequency questionnaire at baseline. Cox proportional hazards models were used to compute hazard ratios (HRs) and 95% confidence intervals (CIs) for quartiles of intake and to perform trend tests across sex-specific quartiles with adjustment for relevant confounders.

Results: We identified 1,553 invasive CRC cases among 49,136 Japanese Americans (23,595 men and 25,541 women) during a mean follow-up of 19 years. White rice consumption was not associated with overall CRC incidence in men (P_trend = 0.11) or women (P_trend = 0.56). After excluding participants with a history of diabetes, the inverse associations were significant for CRC (P_trend = 0.03, HR for quartile 4 [Q4] vs quartile 1 [Q1], 0.81; 95% CI, 0.64–1.03) and tumors of the distal colon (P_trend = 0.006, HR for Q4 vs Q1, 0.66; 95% CI, 0.44–0.99) among men but not women.

Conclusion: White rice consumption was not associated with an increased risk of overall CRC among Japanese Americans. An inverse association was observed with risk of CRC and distal colon cancer in men without a history of diabetes.

Background: Developmental dysplasia of the hip (DDH) is a cluster of hip development disorders that affects infants. The incidence of DDH-related dislocation (DDH-dislocation) is reportedly 0.1–0.3%; however, the nationwide incidence of DDH-dislocation in Japan has not been previously reported. The primary aim of this study was to report the nationwide incidence of DDH-dislocation in Japan using the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB), and to examine its regional variation across Japan.

Methods: This was a retrospective birth cohort study using the NDB. Data on patients born between 2011 and 2013 and assigned DDH-dislocation-related disease codes during 2011–2018 were extracted. Among these, patients who underwent treatment for DDH-dislocation between 2011 and 2018 were defined as patients with DDH-dislocation.

Results: Across the 2011, 2012, and 2013 birth cohorts, 2,367 patients were diagnosed with DDH-dislocation, yielding the nationwide incidence of 0.076%. Region-specific incidence rates were almost similar across Japan. Secondary analyses revealed that 273 (11.5%) patients were diagnosed at the age of ≥1 year. The effect of birth during the cold months on the incidence of DDH-dislocation was significant (relative risk [RR] = 1.89, 95% confidence interval [CI]: 1.75–2.06). The risk of DDH-dislocation among girls was approximately seven times higher than that among boys.

Conclusion: This is the first study to report the nationwide incidence of DDH-dislocation in Japan, which was estimated at 0.076%. The regional variation was trivial and unlikely to be clinically significant. Thus, the incidence rates were approximately equal across all regions in Japan.

Background: Postpartum depression (PPD) has been associated with adverse health outcomes, including maternal suicide. Mode of delivery has been suggested to be a risk factor for PPD, but no large cohort study has examined the association between mode of delivery and PPD. We aimed to examine the association between mode of delivery and risks of PPD at 1 and 6 months after childbirth.

Methods: In a nationwide study of 89,954 mothers with a live singleton birth, we examined the association between mode of delivery and risks of PPD. PPD was evaluated using the Edinburgh Postnatal Depression Scale (≥13) at 1 and 6 months after childbirth. Odds ratios (ORs) with 95% confidence intervals (CIs) of PPD were calculated using multivariable logistic regression analyses after adjustment of antenatal physical, socioeconomic, and mental factors.

Results: Among 89,954 women, 3.7% and 2.8% had PPD at 1 and 6 months after childbirth, respectively. Compared with unassisted vaginal delivery, cesarean section (CS) was marginally associated with PPD at 1 month but not at 6 months; adjusted ORs were 1.10 (95% CI, 1.00–1.21) and 1.01 (95% CI, 0.90–1.13), respectively. The association with PPD at 1 month was evident in women with antenatal psychological distress (adjusted OR 1.15; 95% CI, 1.03–1.28). The observed associations were attenuated after adjusting for infant feeding method.

Conclusion: Women who had antenatal psychological distress and underwent CS delivery may be regarded as a target for monitoring PPD.

Background: Metabolic syndrome (MetS) has been associated with various chronic diseases that may lead to long-term sickness absence (LTSA), but there is lacking information on the direct association between MetS and LTSA. The present study aimed to investigate the all-cause and cause-specific associations between MetS and the risk of medically certified LTSA among Japanese workers.

Methods: We recruited 67,403 workers (57,276 men and 10,127 women), aged 20–59 years from 13 companies in Japan during their health check-ups in 2011 (11 companies) and 2014 (2 companies), and we followed them for LTSA events (≥30 consecutive days) until March 31, 2020. MetS was defined according to the Joint Interim Statement. A Cox proportional hazards regression model was used to estimate hazard ratios (HRs) and its 95% confidence intervals (CIs) for LTSA associated with MetS and its components.

Results: During 408,324 person-years of follow-up, 2,915 workers experienced LTSA. The adjusted HR for all-cause LTSA was 1.54 (95% CI, 1.41–1.68) among those with MetS compared to those without MetS. In cause-specific analysis, HRs associated with MetS significantly increased for LTSA due to overall physical disorders (1.76); cardiovascular diseases (3.16); diseases of the musculoskeletal system and connective tissue (2.01); cancers (1.24); obesity-related cancers (1.35); mental, behavioral, and neurodevelopmental disorders (1.28); reaction to severe stress and adjustment disorders (1.46); and external causes (1.46). The number of MetS components were also significantly associated with increased LTSA risk.

Conclusion: MetS was associated with an increase in the risk of LTSA due to various diseases among Japanese workers.

Background: The number of people with cognitive impairment, including dementia, in the world is steadily increasing. Although the consumption of isoflavones and soy is associated with a reduced risk of cardiovascular disease, it might also be associated with cognitive impairment. The low number of studies investigating the association between soy/isoflavone intake and cognitive function warrant additional research.

Methods: The Japan Public Health Center-based prospective (JPHC) Study is a large population-based cohort. Midlife dietary intake of soy and the isoflavone genistein was assessed on two occasions: in the years 1995 and 2000. In 2014–2015, 1,299 participants from Nagano prefecture completed a mental health screening. Of these, a total of 1,036 participants were included in analyses. Logistic regression was used to determine Odds Ratios (OR) and 95% Confidence Intervals (CI) for the association between midlife energy-adjusted genistein and soy food intake and cognitive impairment.

Results: There were 392 cases of cognitive impairment (346 cases of MCI and 46 cases of dementia). Compared to the lowest dietary quartile of energy-adjusted genistein intake, the highest quartile was significantly associated with cognitive impairment (OR = 1.51; 95% CI, 1.02–2.24; P for trend = 0.03) in the final multivariable analysis.

Conclusion: High midlife intake of the isoflavone genistein is associated with late-life cognitive impairment.

Background: In Japan, ten percent of single-parent households are led by fathers. Taking care of children as a single father is very stressful and could put a strain on their health. It is very important to prevent and identify psychological distress among fathers for both their own health and to avoid negative impacts on children. This study aims to determine the prevalence of and factors associated with psychological distress among single fathers and understand how it is different from partnered fathers.

Methods: We used data from the Comprehensive Survey of Living Conditions 2016. Psychological distress, assessed using the K6 scale, was analyzed among 868 single and 43,880 partnered fathers. Logistic regression analysis was performed to assess the risk factors for psychological distress, such as employment type, sleep hours, and smoking and drinking habits.

Results: Single fathers had a higher proportion (8.5%) of psychological distress compared to partnered fathers (5.0%). A larger percentage of single fathers had a lower educational level and were more likely to be non-regular workers, self-employed, or unemployed than partnered fathers. Among single fathers, the crude and adjusted odds ratio for employment type and sleep hours were significantly associated with psychological distress.

Conclusion: As single parents who are self-employed or directors are likely to have significantly reduced psychological distress than those with regular jobs, measures are needed to improve the work-family balance for non-self-employed fathers. There is a need to provide greater financial assistance and other social welfare support to single parents to ensure their and their children’s good health.