Lifestyle-related factors that explain disaster-induced changes in socioeconomic status and poor subjective health: a cross-sectional study from the Fukushima health management survey

BACKGROUND Socioeconomic status (SES) and lifestyle-related factors are determinants of subjective health. However, changes in SES are inevitable in times of natural disaster, while lifestyle-related factors remain modifiable. The aim of this study was to use a cross-sectional approach to examine lifestyle-related factors that may attenuate the negative impact of disaster-induced changes in SES on poor subjective health. METHODS We analyzed 33,350 men and women aged 20-64 years who were living in evacuation zones due to the radiation accident in Fukushima, Japan. Disaster-induced changes in SES were defined by living arrangements and working conditions. Using Poisson regression analysis adjusted for confounders (model 1) and lifestyle-related factors as intermediate variables (model 2), we compared the prevalence ratios (PRs) of poor subjective health of participants who did not undergo disaster-induced changes in SES (did not become unemployed, income did not decrease, and living in relative's home/own home) with that of participants who did undergo disaster-induced changes in SES (became unemployed, decreased income, or lived in an evacuation shelter, temporary housing, or rental housing/apartment). We calculated the percentage of excess risks explained by lifestyle-related factors as follows: ((PRmodel 1 - PRmodel 2)/(PRmodel 1-1)) × 100. RESULTS Disaster-induced changes in SES were significantly associated with poor subjective health. The PRs (95% CIs) among participants who underwent disaster-induced changes in SES were 2.02 (1.81-2.24) for men and 1.80 (1.65-1.97) for women. After adjusting for lifestyle-related factors, we found that the PRs in men and women were remarkably attenuated, decreasing to 1.56 (1.40-1.73) and 1.43 (1.31-1.55), respectively. Controlling for lifestyle-related factors resulted in PR attenuation by 45.1% (men) and 46.3% (women). Satisfaction of sleep and participation in recreation and community activity particularly contributed to this attenuation. CONCLUSIONS While disaster-induced changes in SES are unavoidable, lifestyle-related factors have the potential to attenuate the impact of these changes on poor subjective health.