Increased risk of dementia in the aftermath of the 2011 Great East Japan Earthquake and Tsunami

Abstract

No previous study has been able to examine the association by taking account of risk factors for dementia before and after the disaster. We prospectively examined whether experiences of a disaster were associated with cognitive decline in the aftermath of the 2011 Great East Japan Earthquake and Tsunami. The baseline for our natural experiment was established in a survey of older community-dwelling adults who lived 80 km west of the epicenter 7 mo before the earthquake and tsunami. Approximately 2.5 y after the disaster, the follow-up survey gathered information about personal experiences of disaster as well as incidence of dementia from 3,594 survivors (82.1% follow-up rate). Our primary outcome was dementia diagnosis ascertained by in-home assessment during the follow-up period. Among our analytic sample (n = 3,566), 38.0% reported losing relatives or friends in the disaster, and 58.9% reported property damage. Fixed-effects regression indicated that major housing damage and home destroyed were associated with cognitive decline: regression coefficient for levels of dementia symptoms = 0.12, 95% confidence interval (CI): 0.01 to 0.23 and coefficient = 0.29, 95% CI: 0.17 to 0.40, respectively. The effect size of destroyed home is comparable to the impact of incident stroke (coefficient = 0.24, 95% CI: 0.11 to 0.36). The association between housing damage and cognitive decline remained statistically significant in the instrumental variable analysis. Housing damage appears to be an important risk factor for cognitive decline among older survivors in natural disasters.