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Two frequently encountered but underrecognized challenges for causal inference in studying the long-term health effects of disasters among survivors include 1) time-varying effects of disasters on a time-to-event outcome and 2) selection bias due to selective attrition. In this paper, we review approaches for overcoming these challenges and demonstrate application of the approaches to a real-world longitudinal data set of older adults who were directly affected by the 2011 Great East Japan Earthquake and Tsunami (n = 4,857). To illustrate the problem of time-varying effects of disasters, we examined the association between degree of damage due to the tsunami and all-cause mortality. We compared results from Cox regression analysis assuming proportional hazards with those derived using adjusted parametric survival curves allowing for time-varying hazard ratios. To illustrate the problem of selection bias, we examined the association between proximity to the coast (a proxy for housing damage from the tsunami) and depressive symptoms. We corrected for selection bias due to attrition in the 2 postdisaster follow-up surveys (conducted in 2013 and 2016) using multivariable adjustment, inverse probability of censoring weighting, and survivor average causal effect estimation. Our results demonstrate that analytical approaches which ignore time-varying effects on mortality and selection bias due to selective attrition may underestimate the long-term health effects of disasters.

Background Long-term care (LTC) costs create burdens on aging societies. Maintaining oral health through dental visits may result in shorter LTC periods, thereby decreasing LTC costs; however, this remains unverified. We examined whether dental visits in the past 6 months were associated with cumulative LTC insurance (LTCI) costs. Methods This cohort study of the Japan Gerontological Evaluation Study targeted independent adults aged≥65 years in 2010 over an 8-year follow-up. We used data from a self-reported questionnaire and LTCI records from the municipalities. The outcome was cumulative LTCI costs, and exposure was dental visits within 6 months for prevention, treatment, and prevention or treatment. A 2-part model was used to estimate the differences in the predicted cumulative LTCI costs and 95% confidence intervals (CIs) for each dental visit. Results The mean age of the 8 429 participants was 73.7 years (standard deviation [ SD ] = 6.0), and 46.1% were men. During the follow-up period, 17.6% started using LTCI services. The mean cumulative LTCI cost was USD 4 877.0 (SD  = 19 082.1). The predicted cumulative LTCI costs were lower among those had dental visits than among those who did not. The differences in predicted cumulative LTCI cost were −USD 1 089.9 (95% CI = −1 888.5 to −291.2) for dental preventive visits, −USD 806.7 (95% CI = −1 647.4 to 34.0) for treatment visits, and −USD 980.6 (95% CI = −1 835.7 to −125.5) for preventive or treatment visits. Conclusions Dental visits, particularly preventive visits, were associated with lower cumulative LTCI costs. Maintaining oral health through dental visits may effectively reduce LTCI costs. [ABSTRACT FROM AUTHOR]

Objective This study aimed to determine whether the frequency of eating together is associated with the incidence of functional disability in older adults who live alone. Methods This 6-year observational prospective cohort study utilised self-reported questionnaires. Data were drawn from the participants of the Japan Gerontological Evaluation Study project between 2016 and 2022. The participants were independent older adults aged ≥65 years living alone in Japan. The primary outcome was the incidence of functional disability during the follow-up period, with the self-reported frequency of eating together serving as the explanatory variable. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards models after adjusting for confounders associated with incident functional disability. Results Among the 7167 participants, the mean age at baseline was 75.3 ± 6.5 years and 69.2% were female. About, 12.8% of participants (n  = 917) developed functional disabilities during the observation period. The incidence rates were 11.7% for 'every day', 11.3% for 'several times a week', 11.5% for 'several times a month', 12.7% for 'several times a year' and 19.0% for 'seldom'. The frequency of eating together 'seldom' was significantly associated with an increased incidence of functional disability (HR: 1.55, 95% CI: 1.10–2.18). Conclusion Among older adults living alone, infrequent eating together ('seldom') was identified as a risk factor for developing functional disability. [ABSTRACT FROM AUTHOR]