Risk Factor for Incident Functional Disability and the Effect of a Preventive Exercise Program: A 4-Year Prospective Cohort Study of Older Survivors from the Great East Japan Earthquake and Nuclear Disaster

Objective: The aim of this study is to assess the risk factors for incident functional disability among long-term evacuees of Iitate village after Great East Japan Earthquake and nuclear disaster (GEJE). We also investigated the effectiveness of exercise classes as an intervention measure in this situation. Methods: 1159 subjects (75.2 ± 5.8 years, 57.5% female) were included at baseline, and followed-up for four years. Cox proportional hazard regression analysis was used to estimate the hazard ratio (HR) of incident functional disability according to the presence of risk factors evaluated by the municipality’s self-assessment Basic Checklist (BCL). Evacuees from Iitate who participated in the exercise classes and those who did not were matched using the propensity scores, which were then used to obtain the HR of incident functional disability. Results: New functional disability occurred in 280 (24.2%) participants during the follow-up. Participants who scored negative for the “Physical function” domain in the BCL had a HR of 2.04 (95% CI: 1.54–2.69) for incident functional disability when compared to those who scored positive for this domain. Similarly, the HR for “Cognitive function” was 1.37 (CI: 1.06–1.77), and 1.60 (CI: 1.24–2.08) for “Depression”. Using a Cox proportional hazard regression model, both the group with low-participation in the exercise program and the group with high-participation in the exercise program had a significantly lower rate of incident functional disability compared to those who did not participate at all (HR = 0.27, CI: 0.16–0.46; HR = 0.30, CI: 0.12–0.74, respectively). Conclusions: Pre-disaster BCL domains were useful to identify individuals at risk of functional disability after a major socio-technical disaster. Therefore, this instrument can be used to identify at-risk older adults who would benefit from early exercise programs to prevent incident functional disability.