Background: Dietary diversity is associated with enhanced cognitive function and reduced dementia risk among older adults; however, its relationship with structural brain ageing remains unclear. We examined cross-sectional and longitudinal associations between dietary variety score (DVS) and brain volume among older Japanese adults.

Methods: We analysed data from the Neuron to Environmental Impact across Generations (NEIGE) cohort, a population-based longitudinal study of community-dwelling Japanese adults aged 65–84 years. The analysis included 279 participants with baseline and follow-up magnetic resonance imaging (MRI) data. Dietary diversity was assessed at baseline using the DVS based on the consumption frequency of 10 food groups. Hippocampal and total grey matter volumes were measured using MRI at baseline (2017) and follow-up (2021). Cross-sectional associations were examined using multivariable linear regression models, and longitudinal associations were assessed using linear mixed-effects models adjusting for confounders.

Results: Mean follow-up was 4.1-year (SD 0.2). In cross-sectional analyses, DVS was not significantly associated with brain volume. In longitudinal mixed-effects models, the interaction between baseline DVS and duration was not significantly associated with changes in total grey matter volume (−128.11 mm³/year per 1-point increase in DVS; 95% CI, −267.86 to 11.65; p = 0.07). Similarly, no significant association was observed for hippocampal volume (-0.44 mm³/year per 1-point DVS; 95%CI, -3.52 to 2.65; p=0.78).

Conclusions: Dietary diversity was not significantly associated with brain volume or with the rate of change in brain volume over time among older Japanese adults.

Background

Previous studies have reported educational inequalities in all and site-specific cancer mortality. However, the mechanisms underlying this association remain unclear. We investigated the association between educational level and all- and site-specific cancer mortality and examined potential mediating factors.

Methods

We conducted a longitudinal study using data from the Japan Gerontological Evaluation Study (JAGES), initiated in 2010 with 7-year follow-up targeting independent adults aged ≥65 years. Self-report questionnaire data were linked to mortality records from municipal registries. Educational level was exposure (<10/10–12/>12 years for competing risk models and <10/≥10 years for causal mediation analysis). All- and site-specific cancer mortality were outcomes. Competing risk models estimated sub-distribution hazard ratios (SHRs) and 95% confidence intervals (CIs). Causal mediation analysis assessed mediating effects of smoking status, drinking status, health examination, vegetable and/or fruit intake, and walking time.

Results

Among 43,478 participants (46.6% men, mean age 73.7 years), the 7-year mortality from all cancers was 5.1%. Low educational level was associated with higher all-cancer mortality (SHR for the lowest compared with the highest 1.27; 95%CI, 1.13–1.44). Similar associations were observed for tracheal and lung, and esophageal cancer mortality. The association between educational level and all cancer mortality was significantly mediated by smoking status (5.6%), health examination (8.0%), and walking time (7.1%), but not by drinking status and vegetable and/or fruit intake.

Conclusion

Lower educational level was associated with a higher risk of all cancer, tracheal and lung cancer, and esophageal cancer mortality. Health behaviors partially explained these associations.

Background: Frailty is a growing public health concern, with emerging evidence highlighting the importance of social determinants, including external and intra-household isolation. This study examined the association between intra-household isolation and frailty among community-dwelling older adults in Japan and explored whether external social connections modified this association.

Methods: Data were obtained from the 2023 baseline survey of the Wako Cohort Study, including 6,429 participants aged ≥65 years in Wako City, Saitama Prefecture, without long-term care certification levels 3–5 (men: 45.0%; mean age: 76.5 years). Intra-household isolation was defined as living with others but having minimal interaction (talking <15 min/day and spending most time alone at home). Frailty was assessed using the 25-item Kihon Checklist. Modified Poisson regression analysis estimated the associations, adjusting for sociodemographic factors, health behaviors, health conditions, and external social connections.

Results: Intra-household isolation was observed in 5.3% of participants, while 21.0% lived alone. Frailty was observed in 28.3% of participants. Individuals with intra-household isolation were more likely to be frail than non-isolated individuals (prevalence ratio [95% confidence interval]: 1.42 [1.26–1.59]). This association remained significant when compared with individuals living alone (1.34 [1.16–1.54]) and was stronger among those aged 65–74 years than those aged ≥75 years. No significant interaction was observed between intra-household isolation and external social connections.

Conclusion: Intra-household isolation among cohabiting older adults was independently associated and showed a stronger association with frailty than living alone. These findings suggest that living with others does not necessarily have protective effects unless meaningful interactions exist.

Background: Socioeconomic inequalities in disability-free life span have been widening. We evaluated the mediating role of multiple modifiable risk factors, including tooth loss, on socioeconomic inequalities in disability onset and mortality among Japanese older adults.

Methods: This prospective cohort study utilized data from the Japan Gerontological Evaluation Study, targeting adults aged ≥65 years. The 2013 baseline questionnaire survey participants were followed until 2022 (n = 48,474; median follow-up, 9.0 years). Time-varying mediators were also assessed in questionnaire surveys in 2016 and 2019. Discrete-time survival analysis estimated the association of socioeconomic status (SES)—a standardized principal component score incorporating household income, wealth, and years of education—with disability or mortality onset. The Karlson–Holm–Breen method decomposed total effects into pathways through 11 mediators, including tooth loss and major risk factors for disability and mortality.

Results: During the follow-up, 29.1% became disabled or died. Compared to the highest SES group, the lowest SES quartile group exhibited a hazard ratio of 1.26 (95% confidence interval [CI], 1.19–1.34) for disability or mortality. Tooth loss exhibited the second largest indirect effect (proportion mediated 12.4%; 95% CI, 8.0–17.2), following moderate depression (16.0%; 95% CI, 11.7–21.5). Tooth loss exhibited the strongest association with SES, attributing to the large indirect effect.

Conclusion: The findings suggest that tackling inequalities in tooth loss may be an effective way to reduce socioeconomic inequalities in a disability-free life span.

Background: Herpes simplex virus encephalitis (HSE) is a rare but life-threatening condition. While the disease has been well characterized in Western countries, large-scale epidemiological data from Japan are lacking.

Methods: Using the Ministry of Health, Labour and Welfare (MHLW) Diagnosis Procedure Combination (DPC) Study Group database, we identified patients hospitalized with HSE between July 2010 and March 2023. Patients were identified using International Classification of Diseases, 10^th Revision codes. Nationwide incidence was estimated by multiplying the observed case counts by the annual ratio of total discharges in the national MHLW-DPC database to those in the DPC Study Group. We used generalized estimating equations to account for clustering within hospitals in multivariable models. In-hospital mortality and functional and neurological outcomes were assessed. Multivariable logistic regression identified prognostic factors.

Results: A total of 6,788 patients were identified. The annual incidence of HSE ranged from 5.7 to 8.2 per 100,000 hospitalizations. Overall, in-hospital mortality was 6.0%. Of 6,378 survivors, 2,295 (36.0%) had a Barthel Index score ≤90 and 1,602 (25.1%) had impaired consciousness (Japan Coma Scale ≥1) at discharge. A composite poor outcome (death or impaired consciousness) occurred in 2,012 (29.6%). Older age (especially ≥80 years), impaired consciousness at presentation, and comorbidities such as congestive heart failure, chronic renal disease, malignancy, and underweight status were associated with in-hospital mortality and poor outcomes.

Conclusion: This multicenter analysis of HSE in Japan showed that HSE was associated with substantial disability among survivors, in addition to non-negligible mortality. Our findings highlight the need for post-acute rehabilitation to reduce the burden of residual disability.

Background: During the coronavirus disease 2019 (COVID-19) pandemic, global influenza activity sharply declined due to extensive non-pharmaceutical interventions (NPIs). Understanding how influenza activity rebounded after these interventions were lifted is critical for informing future respiratory virus control strategies.

Methods: We conducted a descriptive analysis of the temporal characteristics of weekly number of influenza-like illness (ILI) cases, ILI%, influenza-positive cases, and influenza-positive rates. Poisson log-link regression models, incorporating meteorological factors using data from 2013 to 2019, were established to predict the weekly influenza-positive rate under a counterfactual scenario without COVID-19 interventions in 2022–2023.

Results: Our findings indicate that the cancellation of COVID-19-related NPIs had a notable impact on increasing influenza transmission. Children under 5 years old exhibited the highest ILI cases. The influenza positivity rate surged to 34.35% during the pandemic relaxation, surpassing pre-pandemic (24.53%) and pandemic (9.56%) rates. During the pre-COVID-19 period, various influenza virus subtypes were co-circulated, with the predominant subtype varying. However, during the COVID-19 pandemic period, the dominant strains were influenza A/H1N1 and influenza B/Victoria lineage, while influenza A/H3N2 predominated in the pandemic relaxation period.

Conclusion: The marked resurgence of influenza activity in Shenzhen following the lifting of COVID-19-related NPIs underscores the need for sustained surveillance and preparedness for concurrent or sequential respiratory virus outbreaks.

Background: Pre-pregnancy underweight (BMI <18.5 kg/m²) is notably prevalent among reproductive-aged Japanese women, affecting approximately 20%, compared to less than 10% in Western countries. However, its overall impact on maternal and infant outcomes in Japanese populations has not been systematically evaluated.

Methods: We conducted a systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. MEDLINE, EMBASE, CINAHL, PsycINFO, Cochrane Library, and Ichushi were searched from inception to February 2024. Cohort and case-control studies examining associations between pre-pregnancy underweight and perinatal outcomes in Japanese women with singleton pregnancies were included. Primary outcomes were low birth weight (LBW), small for gestational age (SGA), and preterm birth (PTB). Random-effects models calculated pooled odds ratios (ORs) with 95% confidence intervals (CIs).

Results: Thirty-four studies were analyzed. Pre-pregnancy underweight significantly increased risks of LBW (OR 1.61; 95% CI, 1.38–1.86), SGA (OR 1.59; 95% CI, 1.55–1.63), and PTB (OR 1.23; 95% CI, 1.19–1.26). Mean birth weight was 115.02 g lower (95% CI, −128.05 to −101.99) in underweight mothers.

Conclusion: Pre-pregnancy underweight among Japanese women is significantly associated with increased risks of adverse perinatal outcomes. Notably, these elevated risks persist despite the high background prevalence of underweight, suggesting that their adverse effects are not diminished in populations where it is more common. These findings underscore the importance of increasing awareness of preconception care and emphasize the need to optimize pre-pregnancy weight.

Background: Seasonal influenza is a recurrent respiratory infection, and timely detection is essential for public health. In Japan, surveillance is conducted through sentinel medical institutions under the National Epidemiological Surveillance of Infectious Diseases (NESID). Recently, access to large claims databases, such as the JMDC claims database (JMDCdb), has increased. While both are sample-based systems, JMDCdb covers a much larger population. We aimed to assess consistency between these sources in estimating influenza cases and the effective reproduction number (R_t) and to explore their utility in epidemic analysis.

Methods: We analyzed data from week 36 of 2016 to week 35 of 2019. Influenza cases were estimated from NESID (reported cases and cases per sentinel) and JMDCdb (cases with influenza-related diagnoses and antiviral prescriptions). Daily infection counts were derived to estimate R_t.

Results: Although minor differences appeared at epidemic peaks, estimates from NESID reports aligned well with JMDCdb. Estimates based on cases per sentinel were lower. R_t values were consistent across data sources. R_t exceeded 1.0 when cases per sentinel surpassed 0.2–0.3. Using a threshold of 0.25 cases per sentinel enabled detection of epidemic onset 4–5 weeks earlier than current standards.

Conclusion: Claims data, such as those from JMDCdb, may be useful for retrospective examination of influenza trends. Moreover, a detailed analysis of the number of cases reported per sentinel suggested the potential to propose threshold values that enable earlier prediction of epidemics than conventional criteria.

Background: Angiopoietin-like protein 2 (ANGPTL2) is an aging-associated protein that contributes to the maintenance of tissue homeostasis. Excessive activation of ANGPTL2 disrupts this homeostatic process, leading to several adverse conditions, such as chronic inflammation, abnormal tissue remodeling, insulin resistance, and carcinogenesis. Nevertheless, only a very few studies have investigated the relationship between circulating ANGPTL2 concentrations and cause-specific mortality risk in the general population.

Methods: We conducted a prospective cohort study involving 2,912 community-dwelling Japanese adults aged ≥40 years with no prior history of cardiovascular diseases or cancer. Baseline serum ANGPTL2 concentrations (collected in 2002–2003) were quantified, and the participants were followed up for a median of 15.2 years. Hazards ratios (HRs) and 95% confidence intervals (CIs) for all-cause and cause-specific mortality were estimated using Cox proportional hazards models.

Results: During the follow-up period, 601 participants died (139 from cardiovascular diseases, 200 from cancer, 142 from infectious diseases, and 120 from other causes). Higher serum ANGPTL2 levels were significantly associated with increased risks of all-cause and cause-specific mortality (HR [95% CI] per 1-SD increment in log-transformed serum ANGPTL2 concentration: 1.34 [1.23–1.47] for all-cause mortality; 1.28 [1.06–1.55] for cardiovascular death; 1.31 [1.12–1.53] for cancer death; and 1.27 [1.05–1.54] for death from infectious diseases) after adjustment for potential confounders. These associations were modestly attenuated after additional adjustment for mediators related to insulin resistance and chronic inflammation.

Conclusions: These findings indicate that elevated serum ANGPTL2 concentrations are associated with a higher risk of mortality from multiple causes.

Sleep and physical activity play a crucial role in brain and mental health. While traditional self-reported methods and research-grade accelerometers have several limitations, consumer-grade wearable devices, such as Fitbit, allow continuous, objective, and real-life data collection. The purpose of this article is to report the study protocol and participant characteristics of a wearable device survey that primarily aims to examine the relationship between brain health and long-term patterns of daily physical activity and sleep.

Nearly 2,000 participants were recruited between September 2022 and December 2023, as part of the Tohoku Medical Megabank Brain Magnetic Resonance Imaging Study, to wear Fitbit Charge 5 devices for 1 year, continuously tracking physical activity and sleep. Additionally, home blood pressure measurements and questionnaire data on housing conditions, psychological distress, and medication were collected every 4 months for a total of four assessments.

The mean age of the participants was 58.5 years and 37.4% were men. For the first 30 days after the recruitment, mean step count was 8,910 steps/day, and a mean total sleep time was 370.4 min/night (approximately 6.2 h). The mean morning systolic blood pressure and diastolic blood pressure were 126.2 and 75.5 mmHg, respectively.

This study provides a unique opportunity to integrate longitudinal consumer-grade wearable data, brain MRI, multiomics data, and comprehensive health records from existing cohorts to advance precision medicine and help prevent mental and neurodegenerative diseases, such as dementia. Limitations include potential selection bias, and a relatively smaller sample size than larger global studies.

In epidemiological research, time-to-event outcomes, commonly referred to as survival outcomes, are a common subject of investigation. Here, we first describe the circumstances under which methods of survival analysis are necessary, review the roles of hazard functions, and discuss the limitations of hazard ratios for causal inference. Second, we explain how confounding and dependent censoring, which are common in observational studies, can be addressed by inverse probability weighting and parametric g-formula estimators. We emphasize that hazards serve as building blocks for estimating counterfactual risks. Third, we summarize recent developments in defining causal estimands in the presence of competing risks, including risk without eliminating competing events, net risk, and cumulative incidence under modified treatment. To illustrate how these challenges are addressed in practice, we revisit a recent clinical study on pharmacological interventions for the onset of dementia. We further empirically compare various estimands in the presence of competing events, including separable effects, through simulations. Our overall aim is to elucidate the need to move beyond routinely used methods of survival analysis, particularly the mere estimation of hazard ratios, if the goal is to draw causal inferences. This paper provides an overview of causal survival analysis, focusing on how confounding, dependent censoring, and competing risks can be addressed to estimate causal parameters of interest (counterfactual survival functions or counterfactual risks), which are interpretable and often meaningful for investigators.

Background: The COVID-19 pandemic severely strained public health systems. In Japan, Public Health Centers faced administrative bottlenecks in patient monitoring and allocation. To address this, Sapporo City introduced COVIMARU, a web-based self-reporting application. This study quantitatively evaluated the impact of this digital tool on patient care site allocation efficiency.

Methods: We conducted a retrospective study using a regression discontinuity design (RDD) using data from Sapporo City's comprehensive COVID-19 database from May 1, 2020, to April 25, 2022. The intervention was COVIMARU implementation for home care on November 12, 2020. The primary outcome was time in days from diagnosis to first care site allocation. We quantified the estimated effect at the cutoff to evaluate the localized impact of the intervention.

Results: The analysis included 130,500 patients. COVIMARU introduction was associated with a significant reduction in mean allocation time at the intervention threshold (estimated effect: -0.96 days (95% CI, -1.39 to -0.20; P = 0.0091). This improvement was not attributable to changes in patient volume. A sensitivity analysis excluding non-working days confirmed the finding (estimated effect: -0.87 days; 95% CI, -1.39 to -0.21; P = 0.008).

Conclusion: The COVIMARU web application significantly reduced patient allocation times, demonstrating that digital health tools can effectively mitigate administrative bottlenecks and improve pandemic response efficiency. Investing in such digital infrastructure is a critical strategy for building resilient public health systems for future emergencies.

Background

North-south differences in context and lifestyle may shape multimorbidity patterns in China. We compared multimorbidity between two northern (Liaoning, Jilin) and two southern (Guangdong, Jiangsu) CNHS provinces in eastern China using association rule mining (ARM) and sequential pattern mining (SPM).

Methods

We analyzed 19,067 adults (≥20 years) and 20 chronic conditions. ARM identified co-occurrence rules and reported support (proportion with the combination), confidence (P(consequent|antecedent)), and lift (observed/expected co-occurrence; >1 indicates positive association). SPM summarized common diagnosis-order sequences using sequence support (percentage of participants exhibiting an ordered sequence). Sensitivity analyses were restricted to self-reported physician diagnoses.

Results

Multimorbidity prevalence was 37.85% (age-standardized 32.84%), higher in northern than southern provinces (41.39% vs. 34.08%; standardized 35.41% vs. 31.04%). Hypertension, hyperuricemia, and diabetes were most common. Cardiovascular/cerebrovascular conditions were more frequent in the north, whereas anemia and kidney stones were more common in the south. ARM suggested metabolic–renal clustering in the south (e.g., CKD→gout, support=1.18%, confidence=26.14%, lift=2.60; gout+anemia→CKD, support=0.55%, confidence=38.89%, lift=3.71) and musculoskeletal–cardiovascular links in the north (e.g., osteoarthritis→spinal disease, support=0.52%, confidence=24.69%, lift=2.22; CTRD→CHD, support=0.63%, confidence=28.24%, lift=1.26). Common SPM sequences included hypertension→hyperuricemia (24.22%) and hypertension→diabetes→hyperuricemia (5.32%); hypertension→hyperuricemia→CKD was more frequent in the south (2.28%), while hypertension→CHD→hyperuricemia was more frequent in the north (5.70%). Sensitivity analyses showed broadly consistent regional contrasts.

Conclusions

Multimorbidity burden and structure differed between the northern and southern provinces, supporting province-tailored prevention and integrated care.

Background: Early childhood offers a foundational window for developmental progress, yet many children in low- and middle-income countries (LMICs) face risks of developmental delay (DD) due to inadequate or harsh caregiving environments. This study investigates the associations between child discipline practices (CDP) and suspected DD and aggressive behavior in Lao People's Democratic Republic (Lao PDR).

Methods: We analyzed nationally representative data from the 2023 Lao Social Indicator Survey III, including 5,007 children aged 24–59 months. CDP was assessed using an 11-item module categorized into non-violent discipline, psychological, and physical punishment. Suspected DD was measured using the Early Childhood Development Index (ECDI2030) tool; aggressive behavior was caregiver-reported. Poisson and multinomial logistic regression models were employed to estimate prevalence ratios (PRs) and odds ratios (ORs), each with 95% confidence intervals (CIs).

Results: The prevalence of suspected DD was 56.3%. Non-violent discipline (adjusted PR: 0.82; 95% confidence interval [CI], 0.80–0.87) and psychological punishment (adjusted PR: 0.90; 95% CI, 0.85–0.95) were associated with lower prevalence of suspected DD, although an interaction analysis suggested the latter effect was evident only when co-occurring with non-violent discipline. Physical punishment was associated with increased prevalence of suspected DD (adjusted PR: 1.07; 95% CI, 1.01–1.15) and higher odds of elevated aggressive behavior (adjusted OR: 2.15; 95% CI, 1.15–4.05).

Conclusion: Non-violent and physical discipline were differentially associated with developmental outcomes. Promoting non-violent caregiving strategies may reduce behavioral risks and support early development in Lao PDR and similar settings.

Background: Physical activity (PA) levels are inversely associated with hip fracture risk, but whether this is the case for other types of fractures, especially vertebral fractures, is unclear. The present study aimed to examine whether PA levels are associated with osteoporotic fracture risk in community-dwelling people.

Methods: This cohort study analyzed 13,558 Japanese people aged 40–74 years (6,756 women and 6,802 men). Information on demographic characteristics, body size, lifestyle, and disease history was obtained by a self-administered questionnaire conducted in the 2011–2013 baseline survey. Levels of total PA excluding sleep, sitting, and other sedentary activities (TPA) were estimated by the metabolic equivalents score (MET-h/d). Incident limb fractures (distal radius, humeral neck, and hip) and vertebral fractures were identified in medical records. A Cox proportional hazards model was used to calculate hazard ratios (HRs).

Results: During a mean follow-up period of 12.1 years, 966 fractures occurred (725 in women and 241 in men). Higher TPA levels were associated with a lower hazard of limb fracture (P for trend=0.0244), with the highest quintile having a lower HR (HR=0.67; 95%CI, 0.49–0.90) than the reference (lowest quintile). Higher LTPA levels were associated with a lower hazard of limb fracture (P for trend=0.0077), with the highest level having a lower HR (HR=0.73; 95%CI, 0.58–0.92) than the reference. No PA measures were associated with vertebral fracture.

Conclusion: Higher levels of PA of any type are associated with a low risk of limb fracture, but not clinical vertebral fracture, in Japanese adults.

Background: Physical frailty is a well-established risk factor for cognitive impairment, but the psychosocial mechanisms underlying this link remain insufficiently understood. Psychological well-being (PWB) may represent a modifiable pathway. This study examined whether PWB mediates the association between physical frailty and incident cognitive impairment, and whether this pathway varies by age or gender.

Methods: We analyzed data from 11,607 cognitively normal adults aged ≥60 years in the Chinese Longitudinal Healthy Longevity Survey (CLHLS, 2008-2018). Frailty was assessed using a deficit-based Frailty Index, PWB using validated multi-item scales, and cognition using the Mini-Mental State Examination. Associations were examined using correlation, multivariable regression, and survival analyses. Causal mediation analysis under a counterfactual framework with 1,000 bootstrap resamples estimated direct and indirect effects, with age- and gender-stratified analyses assessing moderated mediation.

Results: Over a median follow-up of 40.3 months, 19.5% of participants developed cognitive impairment. Frailty was associated with a 40% higher hazard of cognitive impairment (HR=1.40, 95%CI: 1.15-1.71), and PWB mediated 6.5% of this association. The proportion mediated was greatest among adults aged 60-79 years (10.8%) and was not modified by gender.

Conclusions: PWB partially mediates the frailty-cognition association in Chinese older adults, with stronger mediation observed in younger age groups. Enhancing psychological well-being may offer a scalable and modifiable strategy to strengthen cognitive resilience in rapidly ageing societies.

Background: Evidence on factors influencing the association between physical activity (PA) and knee osteoarthritis (KOA) is scarce. The present study aimed to examine this association and explore interactions of PA with sex and age in relation to KOA in Japanese adults.

Methods: This 11-year cohort study included 10,876 community-dwelling individuals aged 40–74 years in Murakami City (Niigata Prefecture, Japan). Data were collected using a self-administered questionnaire (2011–2013). Exposures were self-reported PA levels, and the outcome was clinically diagnosed KOA. Covariates included demographic factors, body size, lifestyle habits, and disease history. Cox proportional hazards models were used to estimate hazard ratios (HRs).

Results: The mean age of participants was 58.0 years. Over a mean follow-up period of 11.1 years, 840 cases of KOA were observed. High total PA levels were associated with a greater KOA risk (P for trend <0.0001), with the highest quartile showing a higher hazard (HR=1.52, 95%CI:1.23–1.87) than the lowest (reference). This association was observed in both males (HR=2.01, 95%CI:1.39–2.93) and females (HR=1.30, 95%CI:1.01–1.66), with a P for interaction of 0.0219. In addition, the association was more pronounced in younger participants (<55 years; HR=2.07, 95%CI:1.25–3.43) and attenuated in older age groups, with a P for interaction of 0.0278. Non-leisure-time PA showed a similar association with KOA as total PA, whereas leisure-time PA did not.

Conclusion: High total and non-leisure-time PA levels were associated with increased KOA risk, and these associations interacted with sex and age in middle-aged Japanese adults.

Evidence-based policymaking increasingly demands integrating real-world data with patient perspectives. However, a methodological gap exists: administrative claims data provide comprehensive coverage but lack subjective insights, whereas patient experience surveys frequently experience selection bias owing to the lack of reliable sampling frames. This study introduces Claims-Based Enumeration Sampling (CBES), a methodology utilizing administrative claims data as a sampling frame to substitute for clinical registries.

By linking survey responses with claims data at the individual level, CBES facilitates the calculation of sampling probabilities and the application of weighting for ensuring representativeness. We demonstrate the practical feasibility of this design through a case study conducted in Tsukuba City, Japan. Targeting National Health Insurance beneficiaries with diabetes, the survey was implemented as an insurer-commissioned administrative operation, successfully overcoming privacy- and data access-related legal hurdles. The resulting dataset revealed crucial insights into patient stigma and socioeconomic disparities, factors invisible to claims analysis alone.

This study discusses the theoretical framework, statistical advantages, and legal solutions related to CBES. We conclude that CBES provides a robust and scalable alternative to conventional methods, empowering policymakers to capture the “silent voices” of patients and advancing patient-centered healthcare policy.

Background: Kawasaki disease (KD) is a vasculitis syndrome of unknown etiology and the leading cause of acquired heart disease in children in developed countries. The Japanese Nationwide Survey of Kawasaki Disease (JNSKD) in Japan has provided valuable epidemiological data since 1970, but has inherent limitations. We aimed to evaluate the utility of the National Database of Health Insurance Claims (NDB) for describing the epidemiologic features of KD.

Methods: We conducted retrospective cohort study compared NDB data (2013-2019) against JNSKD data for the same period. We analyzed demographic characteristics, temporal and geographic distributions, treatment modalities, and cardiac complications.

Results: NDB identified 120,391 KD patients (2013-2019), with JNSKD estimated to cover 94.0% of cases. Demographic characteristics showed strong concordance between datasets (male-to-female ratios: 1.32 vs 1.33; similar age distributions). Initial IVIG administration rates were highly similar (93.74% vs 93.85%). Incomplete KD was significantly underestimated in NDB (8.07% vs 19.48%). NDB revealed adjunctive therapies including urinastatin and tracked increasing infliximab use. Cardiac complication detection in NDB showed limited sensitivity for mild abnormalities (overall 5.0% vs 7.33%). NDB showed higher recorded rates of giant aneurysms (0.53% vs 0.17%) and myocardial infarction (0.15% vs 0.01%).

Conclusions: The NDB provides a valid, complementary data source for KD epidemiological research with near-complete population coverage. While limitations exist for identifying disease subtypes and cardiac complications, its detailed treatment data offer significant advantages for nationwide surveillance and health policy development.

Background: As the global population ages, understanding factors influencing structural brain aging is crucial for dementia prevention. Social networks have emerged as important social factors; however, longitudinal evidence linking specific structural characteristics of social networks to brain volume change remains limited. This study examined whether social network homogeneity and heterogeneity were related to longitudinal changes in brain volume (hippocampus, gray matter, and prefrontal cortex) among community-dwelling older Japanese adults.

Methods: Data were obtained from the Neuron to Environmental Impact Across Generations (NEIGE) study. Participants aged 65–84 years were randomly selected from Tokamachi City, Japan. Of the 527 older adults surveyed at baseline, 279 who underwent magnetic resonance imaging at both baseline (2017) and follow-up (2021) were included. Social relationship (dis)similarities were assessed using ten items, and network homogeneity and heterogeneity domains were derived through factor analysis. Covariates included sociodemographic factors, health behaviors, health conditions, and apolipoprotein E genotype.

Results: Participants were 47.6% male, with a mean age of 73.2 years (SD = 5.1). Multiple linear regression analyses with inverse probability weighting indicated no association between homogeneous social networks and brain volume changes. However, lower network heterogeneity was significantly associated with a greater decline in hippocampal volume. This was particularly pronounced in the right hippocampus.

Conclusion: Greater social network heterogeneity may attenuate age-related hippocampal volume loss in older adults, highlighting potential benefits of social network heterogeneity for structural brain aging and cognitive aging in later life. Further studies are warranted to clarify the underlying mechanisms.

Background: Long-term trends in cancer incidence were reported until 2015 in Japan, but recent data have been limited since the launch of the National Cancer Registry (NCR) in 2016. We analyzed 30-year trends in cancer incidence and mortality, emphasizing the NCR’s establishment.

Methods: Cancer incidence data were obtained from high-quality population-based cancer registries in three prefectures (Yamagata, Fukui, and Nagasaki) from 1985 to 2015, and the NCR extracted data from these prefectures between 2016 and 2021. National cancer mortality data from 1979 to 2023 were obtained from published vital statistics. Trends in age-standardized rates (ASR) calculated using the 1985 Japan Standard Population were examined using joinpoint regression analysis.

Results: The ASR incidence in 2016 (the first year of the NCR) was the highest ever recorded. All-cancer incidence (for both sexes) increased between 1985 and 2021 (annual percentage change, 0.9%; 95% confidence interval [95% CI]: 0.8 to 1.0). For males, all-cancer incidence stabilized after increasing until 2017, whereas for females, it increased after 2002 (1.7%; 95% CI: 1.4 to 2.3). All-cancer mortality (for both sexes) declined between 1997 and 2023 (-1.5%; 95% CI: -1.5 to -1.4), mainly due to decreases in stomach, lung, and liver cancers.

Conclusions: The NCR’s launch and the sharp rise in incidence in 2016 may have influenced trend interpretation and should be considered with caution. A longer observation period is needed before clear secular trends can be established under the NCR data system.

Age-standardization is a key statistical method used in health statistics to adjust rates such as mortality or incidence, enabling comparisons across populations or time points with different age structures. This review traces its historical development, global and country-specific practices, and future directions. The method dates back to the 19th century, with major adoption in the 20th century through the Segi and Doll's World Standard Population. While the World Health Organization (WHO) introduced an updated standard in 2000, the International Agency for Research on Cancer (IARC) continues to use the Segi and Doll's standard in the Cancer Incidence in Five Continents series, prioritizing consistency and comparability in long-term cancer surveillance. Case studies from the IARC, the United States (U.S.), Japan, and the Republic of Korea (Korea) illustrate different responses to changing demographics. The U.S. adopted the 2000 standard with expanded age detail for the elderly population. Japan introduced the 2015 Japan Standard Population to account for its rapidly aging society, though regional data limitations presented challenges. Korea, experiencing one of the fastest aging transitions globally, updated to a 2020 standard for more accurate national and sub-national reporting. The review also emphasizes that age-standardization can obscure important age-specific trends. Methods like Joinpoint clustering help detect divergent trends by age groups. Looking forward, age-standardization remains essential amid global demographic shifts. However, updates of standard populations must balance improved relevance with the need for continuity and robust data. International coordination and digital tools will support more flexible and transparent health statistics in the future.

Background: The Physical Effort Scale (PES) assesses tendencies to approach or avoid physical effort and provides a framework for examining how automatic effort-avoidance tendencies influence physical activity (PA) behavior. To facilitate cross-cultural PA research, this study developed and validated a Japanese version of the PES (PES-JP) following cross-cultural adaptation guidelines. Methods: An online survey was conducted among 398 Japanese aged 20–59 years. Results: Exploratory analyses suggested a two-factor structure of the PES-JP (approach and avoidance), and both subscales demonstrated high internal consistency (α = .92, .87). Concurrent validity was supported by associations with PA. The approach score was positively related to moderate-to-vigorous PA (MVPA; β = .19) and negatively to sitting time (β = –.17). In contrast, the avoidance score showed the opposite pattern (β = –.13 for MVPA, β = .20 for sitting). The global score (approach minus avoidance), which reflects the overall tendency to approach rather than avoid physical effort, showed a similar pattern to the approach dimension (β = .19 for MVPA, β = –.22 for sitting). Test-retest reliability was acceptable (ICCs = .65–.81). Conclusions: The PES-JP demonstrates sound psychometric properties for assessing tendencies toward physical effort in Japanese adults and provides a useful tool for research on individual differences in PA behavior. The scale may also facilitate cross-cultural investigations of how tendencies toward physical effort influence PA across diverse populations.

Background: The coronavirus disease 2019 (COVID-19) pandemic disrupted access to healthcare for homebound older adults, particularly those with cancer. We compared changes in the initiation and outcomes of physician-led home-visit care among older Japanese patients with and without cancer during the pandemic.

Methods: We conducted a retrospective observational study using national medical claims data of patients aged ≥65 years who began physician-led home visits between April 2018 and December 2020 in Japan. The proportions of all-cause death, in-home death, and at least one hospitalization within 90 days after the initiation of home visit care were compared between the pre-pandemic (April 2018 to December 2019) and pandemic periods (January 2020 to December 2020), stratified by cancer diagnosis. Differences between the cancer and non-cancer groups were estimated using linear regression models with an interaction term for cancer status and pandemic period.

Results: Among 509,718 patients (251,311 with cancer), the initiation of home-visit care increased in both groups during the pandemic. All-cause and in-home death rates increased and hospitalization rates decreased in both groups, with greater changes among patients with cancer: 1.6% (95% confidence interval, 1.1 to 2.1) for all-cause death, 3.8% (95% CI, 3.4 to 4.3) for in-home death, and –2.9% (95% CI, –3.7 to –2.2) for hospitalization.

Conclusions: During the COVID-19 pandemic, physician-led home-visit care expanded, and patients with cancer showed a greater shift toward home-based end-of-life care. These findings highlight the need for targeted resource allocation strategies to support home-visit physicians caring for patients with cancer during public health emergencies.

Background:

Despite guideline recommendations to deliver cessation advice, implementation in Japan remains inconsistent. We examined tobacco use prevalence, receipt of healthcare providers' advice, and its association with quit attempts.

Methods:

We analyzed the 2024 wave of a nationwide web-based survey (N=27,374; ages 16–74). Non-probability quota sampling and post-stratification weighting were used to approximate national population distributions. Current (past-30-day) tobacco use was assessed for heated tobacco products (HTPs), cigarettes, non-cigarette combustible tobacco, and dual use (HTPs plus combustible). Exposure was receipt of healthcare providers’ advice, and outcome was quit attempt in the past year. Associations were analyzed using multivariable Poisson regression to obtain adjusted prevalence ratios (APRs) and 95% confidence intervals (CIs).

Results:

Overall, 24.2% reported current any tobacco product use: 12.9% HTPs, 17.8% cigarettes, 3.7% non-cigarette combustible, and 7.3% dual use. Among any tobacco users (N=6,361), 13.2% received advice and 26.7% attempted to quit. Among any tobacco users currently receiving medical care (N=2,779), 20.9% received advice, primarily from doctors (10.3%) and nurses (8.0%), and 29.9% attempted to quit. Compared with no advice, quit attempts were more likely when advice came from one professional (APR, 1.28; 95% CI, 1.05–1.58) or multiple professionals (APR, 1.61; 95% CI, 1.17–2.23). Exclusive HTP users were less likely than exclusive combustible tobacco smokers to attempt quitting (APR, 0.57; 95% CI, 0.41–0.81).

Conclusion:

Receipt of providers’ advice remains low in Japan yet is strongly associated with quit attempts, especially with multi-professional involvement. Policy, training, and system-level supports are needed to strengthen provider engagement.

Background: Limited information has been shown quantitatively assessed factors associated with the risk of secondary transmission in measles index cases.

Method: We collected data on measles index cases reported in Osaka Prefecture between November 2018 and March 2019, along with their close contacts. Secondary attack rates (SARs) in contacts of index cases were calculated and compared depending on the vaccination status, classical or modified measles and other risk factors in index cases. For the multivariate analyses, we used binary logistic regression to adjust for these potential confounding factors on the secondary transmission and calculated the adjusted odds ratio (aOR) for the SARs.

Result: A total of 105 index cases were included, involving 9,846 close contacts, with 72 secondary cases identified. A significant negative association between the number of vaccinations received by index cases and the risk of secondary infection in his/her close contacts (p < 0.01). Index cases who had received one vaccine dose had an aOR of 0.22 (95% CI: 0.08–0.65), while those with two or more doses had an aOR of 0.25 (95% CI: 0.07–0.85). Index cases who did not exhibit all three classic measles symptoms had a significantly lower risk of causing secondary infections compared to those who presented with all three symptoms (aOR: 0.12, 95% CI: 0.03–0.39).

Conclusion: The indirect protective effect of measles vaccination would present important evidence supporting the further strengthening of vaccination policies.

Background: In Korea, grandparents often play a crucial role in childrearing. Therefore, this study investigated the association between family structure and obesity among Korean adolescents.

Methods: Data were analyzed from 3,328 adolescents (1,783 male adolescents and 1,545 female adolescents, aged 10–18 years) who participated in the Korea National Health and Nutrition Examination Survey from 2018 to 2023. Overweight and obesity were defined as a body mass index ≥85^th and ≥95^th percentiles, respectively, based on the 2017 Korean Growth Charts. Family structure was categorized as follows: living with both parents; living with a single parent; living with grandparents and parents; or living with grandparents only. Multivariable logistic regression was used to assess associations, adjusting for age and household income, number of siblings, region, parental education level, frequency of eating out, and regular breakfast intake.

Results: The prevalence of obesity was 15.0% (17.7% in male adolescents and 12.1% in female adolescents). Male adolescents living with grandparents and parents were more likely to be overweight (odds ratio [OR] 2.36; 95% confidence interval [CI], 1.46–3.81) or obese (OR 2.47; 95% CI, 1.46–4.19) than those living with both parents, whereas no significant associations with family structure were observed in female adolescents.

Conclusion: Korean adolescents living with grandparents had higher odds of being overweight or obese. Accordingly, further research is warranted to explore how family structure influences adolescent obesity.

The Tokyo Adolescent Mental Health Study (TAMHS) is an ongoing, school-based longitudinal cohort designed to elucidate the developmental trajectories of mental health among adolescents in Japan and to inform evidence-based strategies for promoting adolescent well-being. Since its inception in 2009, TAMHS has annually tracked adolescents aged 12–18 from a Tokyo secondary school known for its tradition of enrolling twins and triplets. Participants are followed for up to six years. As of 2024, 2,435 adolescents (1,211 boys, 1,196 girls, 28 unspecified), including 551 twins and triplets (22%), have been enrolled. This unique sample composition allows for rigorous comparisons between singletons and multiples to examine the impact of birth plurality on neurodevelopmental and mental health trajectories. High annual retention (96.2%–99.2%) ensures the integrity of longitudinal analyses. Data are collected through self-report questionnaires covering demographics, physical and mental health status, daily habits and lifestyle behaviors, social relationships, behavioral problems, healthcare access, and social and environmental determinants of health. The study has yielded important insights into associations between adolescent lifestyle behaviors and mental health outcomes.

The Community Empowerment and Care for Well-being and Healthy Longevity (CEC) Study is an ongoing, multigenerational, population-based cohort designed to evaluate community-driven lifespan developmental care in a rapidly aging society. Conducted in Village T, Aichi Prefecture, Japan, whose demographic structure broadly resembles national patterns, the study includes residents from infancy to older adulthood. Since 2017, the CEC Study has maintained three age-specific sub-cohorts (0–19, 20–64, and ≥65 years), integrating questionnaire surveys, health examinations, home visits, and administrative records from medical, health, and long-term care systems. A total of 4,638 residents participated in the baseline survey, with 4,079 subjects responding.

The study adopts a community empowerment approach in which residents serve as co-designers and co-implementers of local health initiatives through workshops, monitoring activities, and public feedback sessions. Triennial follow-up surveys and continuous administrative data linkage enable long-term tracking of health trajectories and contextual influences across the life course. The dataset provides detailed information on physical and cognitive function, mental health, lifestyle, social participation, and environmental factors.

Although generalizability may be greatest for regions with demographic and socioeconomic profiles similar to Village T, the CEC Study offers a valuable platform for evaluating real-world, community-led health strategies. Its integration of longitudinal data with empowerment-oriented practice provides insights relevant to evidence-based community health policy and global healthy aging initiatives.

Background: The Diagnosis Procedure Combination (DPC) database is Japan’s most widely used administrative inpatient dataset, supporting epidemiological and health services research. While its validity is established for various diagnoses and procedures, accuracy for intensive care unit (ICU) variables has not been directly evaluated using a clinical registry as the gold standard.

Methods: We conducted a multicenter retrospective validation study using four Japanese ICUs. Patient records from the national ICU registry, the Japanese Intensive Care Patients Database (JIPAD), were matched with corresponding DPC data, retaining only successfully matched patients to evaluate coding accuracy rather than case ascertainment. We assessed binary variables (demographics, comorbidities, diagnoses, interventions, ICU admission, mortality) and continuous variables (demographics, Sequential Organ Failure Assessment [SOFA] scores). We calculated sensitivity and specificity for binary variables and intraclass correlation coefficients (ICCs) for continuous variables.

Results: We included 14,070 ICU admissions. Most binary variables, including demographics, major diagnostic categories, ICU interventions, and mortality, had high sensitivity and specificity (≥80%). Comorbidity specificity exceeded 95%, but sensitivity was <30% for several diseases. Sensitivity was 83.3% for invasive mechanical ventilation but low for noninvasive positive pressure ventilation (5.5%) and high-flow nasal cannula (36.1%), although specificity was high across respiratory supports (97.3%–99.9%). SOFA scores showed moderate agreement (ICC, 0.61). Sensitivity/specificity were 99.1%/100.0% for in-hospital mortality and 96.2%/99.9% for ICU mortality.

Conclusions: The DPC administrative inpatient database accurately captures most key ICU variables, but comorbidities, noninvasive respiratory support, and SOFA scores require caution. These findings support its use for ICU clinical and epidemiological research in Japan.

Background

The Shanghai University of Sport (SUS) Longitudinal Cohort Study (SUS Cohort) was established to investigate the influence of lifestyle and modifiable behavioural factors in early adulthood on the development of non-communicable diseases (NCDs) later in life. The cohort aims to identify novel biomarkers and explore mechanisms underlying chronic diseases using a multi-omics approach.

Methods

The SUS Cohort study is a prospective cohort study of undergraduate students between 2018 and 2019, with follow-ups conducted every two years during early adulthood and every ten years thereafter. Comprehensive data collection includes body composition measurements, lifestyle surveys, physical fitness tests, and clinical laboratory tests. Multi-omics analysis, including genome-wide genotyping, gut microbiome and serum metabolome, is integrated to provide insights into disease pathophysiology.

Results

A total of 1,758 participants aged 18 to 22(mean age: 18.64 ± 3.15) were conducted from baseline surveys, with a follow-up period between September 2021 and September 2022. The median age at baseline was 18 years, and the proportion of female participants was about 871(49.5%). Of the initial participants, 1,055 individuals (60%) completed the follow-up.

Conclusion

The SUS Cohort provides multidimensional data to study how early-life factors influence long-term health outcomes.