Social isolation by housing type 6 years after the Great East Japan Earthquake in Iwate prefecture: longitudinal findings from the Tohoku Medical Megabank community-based cohort study.

Introduction: The Great East Japan Earthquake (GEJE) caused widespread devastation, displacing residents and increasing concerns about social isolation. In this study, we examine the association between housing type at a single postdisaster time point (6 years after the GEJE) and social isolation. Methods: Data from 16 610 participants (5828 men and 10 782 women; mean age 59.4±11.1 years) in the Tohoku Medical Megabank Project Community-based Cohort Study were analysed. Housing was categorised into eight types. Social isolation was measured using the Lubben Social Network Scale-6. Adjusted ORs and 95% CIs were calculated using logistic regression, with analyses stratified by gender and age. Results: Men living in rental housing, particularly those under 65, had a higher risk of social isolation compared with those who remained in their pre-GEJE homes (OR: 1.87, 95% CI 1.06 to 3.28). Men under 65 in rebuilt homes in affected areas also showed reduced risk (OR: 0.41, 95% CI 0.20 to 0.86). Men aged 65 and older in prefabricated or temporary housing were at high risk (OR: 2.19, 95% CI 1.19 to 4.03), but this association disappeared after adjusting for baseline social isolation. Among women, only those aged 65 and older living with friends or relatives had a significantly high risk of social isolation. Conclusions: Housing type influences social isolation after disasters, especially among men. Rental housing may increase isolation risk, while reconstructed homes may reduce it. Disaster recovery policies should address housing-related social isolation.