Background: Reproductive history can be conceptualized as a life-course exposure integrating biological and social factors. Although reproductive factors have been associated with stroke risk and cognitive function, their relationships with structural brain changes remain unclear. Evidence from general population–based studies linking reproductive factors to brain volume, an intermediate marker of cognitive decline, is limited. This study examined whether age at menarche, age at menopause, estrogen exposure duration, and parity are associated with brain volume in postmenopausal women.

Methods: This cross-sectional study included 361 postmenopausal women aged ≥55 years from the Ohasama Study in Japan. Reproductive factors were obtained from a 1998 questionnaire were categorized into quartiles, and MRI data from 2009 to 2019 were analyzed with voxel-based morphometry. Associations were assessed using analysis of covariance adjusted for intracranial volume, age, birth cohort, and BMI. Effect sizes were reported as percent change and standardized effect sizes, with the smallest effect size of interest (SESOI) based on one-year age-related brain volume change.

Results: After covariate adjustment, most associations between reproductive factors and brain volume were attenuated. Earlier age at menarche showed a weak trend toward larger temporal lobe volume (β = 0.59 cm³, 95% CI −0.03 to 1.21; p = 0.06), corresponding to a 0.63% change and 0.06 SD, which was comparable to the SESOI (±0.54% or 0.06 SD). Earlier age at menopause was associated with smaller occipital lobe volume (β = −0.52 cm³, 95% CI −1.01 to −0.03; p = 0.04), corresponding to a −1.08% change and 0.10 SD, exceeding the primary SESOI threshold (±0.64% or 0.06 SD), although confidence intervals included effects smaller than the SESOI. No significant associations were found for estrogen exposure or parity.

Conclusion: Reproductive factors were not associated with moderate or large differences in brain volume in postmenopausal women. The slight, region-specific differences observed were comparable in magnitude to short-term age-related changes. These findings suggest that the clinical significance at the individual level is likely limited. However, subtle associations at the population level cannot be entirely excluded.

Background: Heatstroke is a major public health problem during summer, and meteorological conditions, particularly wet bulb globe temperature (WBGT), strongly influence its occurrence. However, even under similar heat conditions, heatstroke risk may vary according to behavioural patterns on weekdays, weekends/holidays, and post-holiday days. This study aimed to examine whether heatstroke-related ambulance transports in Tokyo vary according to day type after adjusting for WBGT.

Methods: We conducted a time-series analysis using daily heatstroke-related ambulance transports in Tokyo, Japan, during the warm season (May–September) from 2015 to 2025. The days were classified as weekday, weekend/holiday, or post-holiday. The WBGT data for seven locations in Tokyo were used, and the highest daily maximum WBGT served as the heat exposure indicator. Modified Poisson regression models were used to estimate risk ratios (RRs) and 95% confidence intervals (CIs) according to day type, adjusting for the WBGT category at lags 0 and 1 and the calendar year. The same models were applied by age group, severity, and place of occurrence. Four sensitivity analyses, including the use of alternative heat exposure indicators and exclusion of the coronavirus disease 2019 period, were conducted.

Results: After adjusting for WBGT and calendar year, the occurrence of heatstroke-related ambulance transports differed according to day type. Overall, ambulance transports tended to be more frequent on post-holiday days than on weekdays (RR, 1.08; 95% CI, 0.97–1.22). Among adults aged ≥65 years, transports were more frequent on post-holiday days (RR, 1.13; 95% CI, 1.00–1.28) and less frequent on weekends/holidays (RR, 0.87; 95% CI, 0.79–0.96). Among individuals aged <18 years, transports were markedly more frequent on weekends/holidays (RR, 1.80; 95% CI, 1.61–2.03). Weekend/holiday increases were also observed in mild cases and in public indoor and outdoor spaces and educational institutions, whereas cases in residences and workplaces were less frequent. Sensitivity analyses yielded similar results.

Conclusions: Heatstroke-related ambulance transports in Tokyo varied according to day type even after adjusting for WBGT, with distinct patterns across age groups, severity categories, and places of occurrence. Weekly behavioural patterns may contribute to heatstroke risk and warrant consideration in preventive strategies.

Background: Long-term birth cohort studies depend on sustained participant engagement. In such studies, children are not only observed over time but also increasingly become participants who experience, interpret, and evaluate their own involvement in research. However, research on continued participation has focused mainly on parental perspectives, with limited attention to children’s own views or to similarities and differences between parents and children. Against the growing recognition that people in medical research should be understood as participants rather than passive subjects, this study examined research participation experiences and retention intentions in both parents and children within a Japanese birth cohort.

Methods: We conducted a questionnaire survey from September to October 2024 within the Japan Environment and Children’s Study (JECS). The primary outcome was retention intention. Factors associated with retention intention were analyzed separately for parents and children using ordinal logistic regression. Parent-child concordance in retention intention was assessed descriptively using weighted Cohen’s kappa.

Results: Among 1,008 eligible parents of fifth-grade children, 485 responded (response rate, 44%). A large majority of parents (92%) and children (79%) reported willingness to continue participation. Parent–child responses showed moderate agreement (κ = 0.46). In separate adjusted ordinal logistic regression models, stronger parental retention intention was associated with lower perceived questionnaire burden (adjusted odds ratio [aOR]: 5.58, 95% confidence interval [CI]: 3.40–9.17), fewer concerns about possible disagreement with their child (aOR: 5.75, 95% CI: 3.51–9.42), and less difficulty scheduling study activities (aOR: 5.80, 95% CI: 3.50–9.63). In children, stronger retention intention was associated with anticipated gifts (aOR: 7.38, 95% CI: 2.93–18.56), talking with friends about the study (aOR: 6.02, 95% CI: 2.25–16.09), and a desire for peer interaction (aOR: 6.72, 95% CI: 3.39–13.29).

Conclusions: Parents and children both showed generally positive retention intentions, but disagreement was not negligible. Their retention intentions were associated with different participation-related experiences, suggesting that long-term birth cohort studies should attend to participants’ perspectives in age-specific ways. Understanding research participation through both parental and child experiences may help inform more participant-centered engagement strategies and support the quality of long-term cohort research.

Background: Accessible and trustworthy health information sources support informed decisions. Longitudinal evidence on how health information sources influence behavioural changes in community-dwelling populations remains limited. Thus, we examined associations between health information sources and behaviour changes in walking time, balanced meal consumption, and smoking cessation.

Methods: Baseline (2021) and follow-up (2023) survey questionnaires were distributed to residents randomly selected from the 18 residential areas. Health information sources were classified into five categories: print media, television (TV) and radio, the Internet, family and friends, and professionals. Desirable health behaviours were defined as walking for ≥60 min/day; consuming ≥2 meals per day comprising staple grains, main dishes, and side items (SMS); and smoking cessation. Meeting these criteria was classified as good; not meeting them as poor. Improvement was defined as poor at baseline and good at follow-up. Maintenance was defined as good at both surveys. Improvement analyses included participants with poor baseline conditions. Maintenance analyses included those with good baseline conditions. Associations were analysed using multilevel modified Poisson regression models, accounting for clustering within residential areas and adjusting for covariates. Risk ratios (RRs) and 95% confidence intervals (95% CIs) were calculated.

Results: Of the 12 119 baseline participants, 6620 (54.6%) completed the follow-up. The most common health information sources were TV and radio (68.5%), the Internet (56.8%), and print media (48.9%). Use of family and friends as information sources was associated with improvement in walking time (RR: 1.19; 95% CI: 1.02–1.39), as was use of professionals (RR: 1.15; 95% CI: 1.03–1.28). Professionals showed a marginal association with sustained walking time (RR: 1.07; 95% CI: 0.99–1.15). TV and radio was associated with improvement in SMS meal consumption (RR: 1.13; 95% CI: 1.02–1.26), while print media was associated with maintenance of SMS meal consumption (RR: 1.05; 95% CI: 1.01–1.08). No sources were related to smoking cessation.

Conclusions: Health information sources showed distinct associations with improved and maintained health behaviours. Interpersonal sources were relevant for improving walking time, while mass media were linked to dietary improvement and maintenance. These findings suggest tailoring health communication strategies to specific health behaviours.

Depression affects more than 280 million people worldwide and remains a major public health challenge, with limited universally effective preventive strategies. Non-pharmacological interventions have gained increasing attention as complements or alternatives to pharmacotherapy. Shinrin-yoku (forest bathing), a Japanese health practice involving immersion in forest environments, has been reported to relieve stress, enhance immune function, and improve mood. This review synthesizes current evidence on the potential preventive effects of forest bathing on depressive symptoms and examines the mechanistic pathways underlying these effects. A structured search of major scientific databases identified studies investigating psychological responses, neuroendocrine and autonomic regulation, immune-inflammatory markers, and related physiological parameters. Across diverse populations, forest bathing consistently reduced negative mood states, improved vigor, and showed beneficial effects on anxiety, depressive symptoms, sleep quality, and stress biomarkers. Mechanistic evidence suggests that forest bathing may modulate the psycho-neuro-endocrino-immune network through improved sleep, reduced stress hormone levels, enhanced parasympathetic activation, and increases in circulating serotonin, oxytocin, and insulin-like growth factor-1, alongside reduced inflammatory markers. While existing findings are promising, most studies involve small samples, short-term interventions, and limited clinical populations. Future large-scale, controlled studies are needed to confirm long-term effects and to clarify whether forest bathing can contribute to prevention or adjunctive management of depressive symptoms.