The application of the life course approach to social epidemiology has helped epidemiologists theoretically examine social gradients in population health. Longitudinal data with rich contextual information collected repeatedly and advanced statistical approaches have made this challenging task easier. This review paper provides an overview of the life course approach in epidemiology, its research application, and future challenges. In summary, a systematic approach to methods, including theoretically guided measurement of socioeconomic position, would assist researchers in gathering evidence for reducing social gradients in health, and collaboration across individual disciplines will make this task achievable.
Background: The evidence for an association between low intake of vegetables and fruits and increased colorectal cancer risk is inconclusive. Evaluating the colorectal cancer risk associated with continued low intake is important. Methods: We used data of 45 516 and 14 549 subjects aged 40–79 years obtained in the baseline and interim surveys, respectively, from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study). The intake frequency of vegetables and fruits as assessed by a self-administered questionnaire was classified into tertiles of low, middle, and high groups, and the low group was subdivided into 2 equal groups (lower low and higher low groups). Colorectal cancer incidence determined from follow-up was used. Cox’s proportional hazard model was employed to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs), adjusting for covariates. Results: During 598 605 person-years of subject follow-up after baseline, we identified 806 colorectal cancer cases. HRs for the lower low versus the middle and high intake frequencies of vegetables and fruits at baseline were 0.95 (95% CI 0.77–1.16) and 1.08 (95% CI 0.90–1.29), respectively. During 125 980 person-years of subject follow-up after the interim survey, 197 colorectal cancer cases were identified. HRs for the low versus middle and high intake frequencies of vegetables and fruits in both baseline and interim surveys were 0.91 (95% CI 0.61–1.37) and 0.87 (95% CI 0.59–1.27), respectively. Conclusions: Our results suggest that low intake and continued low intake of vegetables and fruits are not strongly associated with colorectal cancer risk.
Background: Whether cigarette smoking and alcohol consumption are associated with the risk of metabolic syndrome (MetS) remains controversial. This study investigated the associations of cigarette smoking and alcohol consumption with MetS in a male population in China. Methods: We conducted a cross-sectional study. A questionnaire was used to collect data on cigarette smoking, alcohol consumption, MetS status, and other related information from 8169 men aged 19–97 years. Logistic regression was used to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between smoking and alcohol consumption and the risk of MetS. Results: The prevalence of MetS was 15.2% in the study population. Proportions of current smokers and drinkers were 48.2% and 46.5%, respectively. Adjusted OR of MetS was 1.34 (95% CI, 1.01–1.79) among smokers who smoked ≥40 cigarettes/day compared with nonsmokers and 1.22 (95% CI 1.03–1.46) for those who consumed 0.1–99 grams of alcohol/day compared with nondrinkers. Adjusted OR was 2.32 (95% CI 1.45–3.73) among ex-drinkers who never smoked, 1.98 (95% CI 1.35–2.91) among ex-drinkers who were current smokers, and 1.34 (95% CI 1.08–1.68) among current drinkers who never smoked compared with those who neither smoked nor drank. There was a significant interaction between smoking and drinking alcohol on MetS (P for interaction is 0.001). Conclusions: Our study indicated that smoking and drinking is associated with higher prevalence of MetS. Interactions between smoking and drinking on the risk of MetS in men in China may also exist. Our findings need to be confirmed in future case-control or cohort studies.
Background: Epidemiologic studies have reported coffee consumption to be associated with various health conditions. The purpose of this study was to examine the relationship of coffee consumption with colorectal cancer incidence in a large-scale prospective cohort study in Japan. Methods: We used data from the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study). Here, we analyzed a total of 58 221 persons (23 607 men, 34 614 women) followed from 1988 to the end of 2009. During 738 669 person-years of follow-up for the analysis of colorectal cancer risk with coffee consumption at baseline, we identified 687 cases of colon cancer (355 males and 332 females) and 314 cases of rectal cancer (202 males and 112 females). We used the Cox proportional-hazard regression model to estimate hazard ratio (HR). Results: Compared to those who consumed less than 1 cup of coffee per day, men who consumed 2–3 cups of coffee per day had an HR of 1.26 (95% confidence interval [CI] 0.93–1.70), and men who consumed more than 4 cups of coffee per day had an HR of 1.79 (95% CI 1.01–3.18). A statistically significant increase in the risk of colon cancer was associated with increasing coffee consumption among men (P for trend = 0.03). On the other hand, coffee consumption in women was not associated with incident risk of colon cancer. Coffee consumption was also not associated with rectal cancer incidence in men or women. Conclusions: This large-scale population-based cohort study showed that coffee consumption increases the risk of colon cancer among Japanese men.
Background: Evidence suggests that Ser326Cys, a genetic polymorphism of human 8-oxoguanine glycosylase 1 (hOGG1), is associated with insulin resistance and type 2 diabetes; however, the underlying mechanism is unclear. Recently, an animal study showed a significant association between the hOGG1 genotype and obesity, although evidence for such an association in humans is limited. The purpose of this study was to examine the association between the hOGG1 genotype and body mass index (BMI) and fasting blood glucose (FBG) levels. Methods: Cross-sectional analysis was conducted using the baseline survey data from a Japan Multi-Institutional Collaborative Cohort Study, which included 1793 participants aged 40–69 years. The hOGG1 polymorphism was detected using a multiplex polymerase chain reaction-based invader assay. Multiple linear regression, analysis of covariance, and logistic regression were used to control for confounding variables. Results: The Cys allele was significantly associated with increased BMI, FBG level, and total cholesterol (TC) level, even after adjustment for gender, age, energy intake, alcohol, smoking, physical activity, and family history of diabetes. An association with BMI was still observed after further adjustment for FBG and TC, but not for the study area (Amami or the mainland). The Cys/Cys genotype was significantly more prevalent in the participants with higher BMI (>27.5 kg/m2). However, the impact of genotype decreased and significance disappeared after adjusting for the study area. Conclusions: The present results suggest that the study area being inside Japan confounds the association between hOGG1 genotype and obesity.
Objective: This study aims to determine whether baseline electrocardiography (ECG) abnormalities, the appearance of new ECG abnormalities, or other clinical characteristics are associated with increased rates of progression to chronic Keshan disease (KD) among patients with latent KD. Methods: Four hundred and fourteen new latent KD patients from a monitored population in China were diagnosed and then followed for 10 years. Baseline and 10-year ECG abnormalities were classified according to the Minnesota Code as major and minor. Using Cox proportional hazards regression models, the addition of ECG abnormalities to traditional risk factors were examined to predict chronic KD events. Results: In 414 latent KD patients with ECG abnormalities, 220 (53.1%) had minor and 194 (46.9%) had major ECG abnormalities. During the follow-up, 92 (22.2%) patients experienced chronic KD events; 32 (14.5%) and 60 (30.9%) of these chronic KD events occurred in the minor and major ECG abnormalities groups, respectively. After adjustment for baseline potential confounders, the hazard ratios and 95% confidence intervals (CIs) for progression to chronic KD in latent KD patients with major ECG abnormalities versus those with minor ECG abnormalities was 2.43 (95% CI 1.58–3.93). Conclusions: Major ECG abnormalities and new ventricular premature complex abnormalities that occurred during the follow-up were both associated with an increased risk of progression to chronic KD. Atrial fibrillation and right bundle branch block with left anterior hemiblock are the most strongly predictive components of major ECG abnormalities. Depending on the model, adding ECG abnormalities to traditional risk factors was associated with improved risk prediction in latent KD.
Background: Uncoded diagnoses in computerized health insurance claims are excluded from statistical summaries of health-related risks and other factors. The effects of these uncoded diagnoses, coded according to ICD-10 disease categories, have not been investigated to date in Japan. Methods: I obtained all computerized health insurance claims (outpatient medical care, inpatient medical care, and diagnosis procedure-combination per-diem payment system [DPC/PDPS] claims) submitted to the National Health Insurance Organization of Kumamoto Prefecture in May 2010. These were classified according to the disease categories of the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). I used accompanying text documentation related to the uncoded diagnoses to classify these diagnoses. Using these classifications, I calculated the proportion of uncoded diagnoses by ICD-10 category. Results: The number of analyzed diagnoses was 3 804 246, with uncoded diagnoses accounting for 9.6% of the total. The proportion of uncoded diagnoses in claims for outpatient medical care, inpatient medical care, and DPC/PDPS were 9.3%, 10.9%, and 14.2%, respectively. Among the diagnoses, Congenital malformations, deformations, and chromosomal abnormalities had the highest proportion of uncoded diagnoses (19.3%), and Diseases of the respiratory system had the lowest proportion of uncoded diagnoses (4.7%). Conclusions: The proportion of uncoded diagnoses differed by the type of health insurance claim and disease category. These findings indicate that Japanese health statistics computed using computerized health insurance claims might be biased by the exclusion of uncoded diagnoses.
Background: Rapid urbanization in China has led to a proliferation of electronic entertainment media among youth. Prolonged screen time (ST; includes watching television and playing on computers, video game consoles, or mobile phones) is linked to poor health profiles. The aim of this study was to report recreational ST behaviors and ST correlates among Chinese adolescents living in two regions with different degrees of urbanization. Methods: A cross-sectional, school-based survey (n = 3461 adolescents; aged 12–14 years old) living in inner-city Shanghai and a peri-urban region of Hangzhou. Students completed a questionnaire including family characteristics, daily ST, and information on family environment related to screen use. Recreational ST was categorized into two groups according to recommendations by the American Academy of Pediatrics (< or ≥2 h/day). Parents reported their own ST and also reported educational attainment as a proxy for socioeconomic status. Results: ST was higher among boys than girls and on weekends than weekdays. Peri-urban girls were more likely to exceed 2 h/day ST compared to inner-city girls on weekends. Having a father with no university degree, mother’s TV viewing ≥2 h/day, no ST rules at home, and eating meals in front of the TV were associated with higher ST on both weekdays and weekends, and regional differences were found for weekend ST. Conclusions: TV viewing and playing on the computer were the most prevalent ST behaviors among Chinese adolescents. Mobile phone playing was less prevalent but persistent throughout the week. More population-level surveillance and research is needed to monitor the trends in ST behaviors and to better understand the characteristics of those who are at risk.
Background: Inconsistent findings in previous studies of the association between sleep duration and changes in body mass index (BMI) may be attributed to misclassification of sleep duration fluctuations over time and unmeasured confounders such as genetic factors. The aim of the present study was to overcome these failings by using repeated measurements and panel data analysis to examine the sleep-BMI association. Methods: Panel data were derived by secondary use of the data from mandatory health checkups at a Japanese gas company. Male non-shift workers aged 19–39 years in 2007 were annually followed until 2010 (n = 1687, 6748 records). BMI was objectively measured, and sleep duration was self-reported. Results: Compared with 7-hour sleepers, panel analysis with the population-averaged model showed a significant increase in BMI among 5-hour (0.11 kg/m2, P = 0.001), 6-hour (0.07 kg/m2, P = 0.038), and ≥8-hour (0.19 kg/m2, P = 0.009) sleepers. On the other hand, after adjustment for unobserved time-invariant confounders using the fixed-effects model, the magnitude of the association was considerably attenuated and no longer significant (5-hour, 0.07 kg/m2, P = 0.168; 6-hour, 0.02 kg/m2, P = 0.631; ≥8-hour sleepers, 0.06 kg/m2, P = 0.460). Conclusions: The longitudinal association between sleep duration and changes in BMI may be upwardly biased by unobserved time-invariant confounders rather than misclassified sleep duration. The net effect of sleep duration on weight gain may therefore be less than previously believed.
Background: The dose-response relationship between glycemic status and lung function has not been thoroughly investigated. We hypothesized that there are continuous and inverse associations between glycemic measures and lung function tests and examined the hypothesis in Japanese adults. Methods: We cross-sectionally investigated associations of hemoglobin A1c (HbA1c) and fasting plasma glucose (FPG) with forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) in 3161 adults who participated in a health screening from 2008 to 2011. The study participants included both diabetic and non-diabetic adults. Multiple linear regression analyses were performed to examine the associations. Results: Inverse associations were observed in both sexes, which were attenuated in women after adjustment for multiple variables. A 1% absolute increase in HbA1c was associated with a −52-mL (95% confidence interval [CI] −111 to 8 mL) difference in FVC and a −25-mL (95% CI −75 to 25 mL) difference in FEV1 in women, and a −128-mL (95% CI −163 to −94 mL) difference in FVC and a −73-mL (95% CI −101 to −44 mL) difference in FEV1 in men. A 10-mg/dL increase in FPG was associated with a −11-mL (95% CI −29 to 8 mL) difference in FVC and a −8-mL (95% CI −24 to 7 mL) difference in FEV1 in women, and a −32-mL (95% CI −44 to −21 mL) difference in FVC and a −19-mL (95% CI −28 to −9 mL) difference in FEV1 in men. Conclusions: Inverse associations between glycemic measures and lung function were observed. Men seem more susceptible to the alteration in FVC and FEV1 than women.
Background: Tinnitus is a common condition and frequently can be annoying to affected individuals. We investigated the prevalence and associated factors for tinnitus in South Korea using the data from the Korea National Health and Nutrition Examination Surveys (KNHANES) during 2009–2011. Methods: KNHANES is a cross-sectional survey of the civilian, non-institutionalized population of South Korea (n = 21 893). A field survey team that included an otolaryngologist moved with a mobile examination unit and performed interviews and physical examinations. Results: Among the population over 12 years of age, the prevalence of any tinnitus was 19.7% (95% CI 18.8%–20.6%). Tinnitus was more prevalent in women, and the prevalence rate increased with age (P < 0.001). Among those with any tinnitus, 29.3% (95% CI 27.3%–31.3%) experienced annoying tinnitus that affected daily life. Annoying tinnitus also increased with age (P < 0.001), but no sex difference was demonstrated (P = 0.25). In participants aged 40 years or older, age, quality of life, depressive mood, hearing loss, feeling of dizziness, and rhinitis were associated with any tinnitus (P < 0.05). Age, hearing loss, history of cardiovascular disease, and stress were associated with annoying tinnitus (P < 0.05). Conclusions: Tinnitus is a common condition, and a large population suffers from annoying tinnitus in South Korea. Public understanding of associated factors might contribute to better management of tinnitus.
Background: To clarify the contribution of patient age to the development of coronary artery lesions (CALs) associated with Kawasaki disease (KD), epidemiologic features and prognostic factors were investigated using hospital-based complete enumeration surveys in a specific area. Methods: Consecutive KD cases identified between October 1999 and September 2012 in Wakayama Prefecture, Japan, were analyzed. The primary outcome measure was the presence/absence of CALs (giant aneurysm, mid- or small-sized aneurysm, and dilatation) on echocardiography 1 month after disease onset. Demographics and medical treatment factors were compared between the patients with and without CALs. Odds ratios (ORs) and 95% confidence intervals (CIs) of explanatory variables (age, gender, and factors related to high-dose intravenous immunoglobulin treatment) for the development of CALs were determined. Results: The median age of the 1415 patients (796 males, 619 females) was 25 months after excluding 2 children of foreign residents; 2.2% of the patients had a past history of KD, and 1.8% showed incomplete presentation. CALs were observed in 3.3% (4.0% of males, 2.3% of females; P = 0.080). The ORs of CALs among patients <11 months old (3.0, 95% CI 1.4–6.6) and those >48 months old (3.1, 95% CI 1.5–6.6) were significantly higher than values in 11- to 48-month-olds. Conclusions: The effect of patient age on the development of CALs was found to be U-shaped, with the bottom at ages 11 to 48 months. This finding was based on a 13-year cohort of consecutive KD cases in a specific area with little selection bias and is consistent with previously reported results.