The association between psychological distress and risk of incident functional disability in elderly survivors after the Great East Japan Earthquake: The mediating effect of lifestyle and bodily pain

Background: We previously reported that psychological distress was associated with an increased risk of functional disability. However, the mechanism of the association remains unclear. Our aim was to estimate the mediating effect of lifestyle and bodily pain on the association among elderly survivors after the Great East Japan Earthquake. Methods: The study population comprised 1037 residents aged ≥ 65 years. The baseline surveys (exposure and mediators) were conducted in 2011. We classified participants into three categories according to their Kessler 6 score (low: 0–9, moderate: 10–12, and high: 13–24) and defined functional disability as certification for long-term care insurance in Japan. The Cox proportional hazards model was used to calculate the hazard ratios (HRs) and 95% confidence intervals (CIs) for incident functional disability according to Kessler 6 categories and explored the mediating effects of lifestyle and bodily pain on the association. Results: During approximately 8 years of follow-up, we documented 271 incident cases of functional disability. Compared with those in the low distress group, the multivariate adjusted HR for incident functional disability was 1.95 (95% CI 1.21–3.13) for those in the high distress group. Time spent walking, going out, and bodily pain significantly mediated the association between psychological distress and incident functional disability by 10.2%, 10.5%, and 10.3% for the high distress group, respectively. Limitations: We did not consider unmeasured confounders and use of appropriate medication. Conclusions: The evaluation and treatment of bodily pain as well as promotion of active lifestyle would be important for preventing disability among disaster survivors.