Social capital and cognitive decline in the aftermath of a natural disaster: a natural experiment from the 2011 Great East Japan Earthquake and Tsunami.

BACKGROUND

We examined prospectively whether social capital mitigates the adverse effects of natural disaster on cognitive decline.

METHODS

The baseline for our study was established seven months before the 2011 Great East Japan Earthquake and Tsunami in a survey of older community-dwelling adults who lived 80 kilometers west of the epicenter (59.0% response rate). Approximately two and a half years after the disaster, the follow-up survey gathered information about personal experiences of disaster as well as incidence of cognitive disability (82.1% follow-up rate). Our primary outcome was cognitive disability (measured on an 8-level scale) assessed by in-home assessment.

FINDINGS

The experience of housing damage was associated with risk of cognitive impairment (coefficient = 0.04, 95% confidence interval: 0.02 to 0.06). Factor analysis of our analytic sample (n = 3,566) established two sub-scales of social capital: a cognitive dimension (perceptions of community social cohesion) and a structural dimension (informal socializing and social participation). Fixed effects regression showed that informal socializing and social participation buffered the risk of cognitive decline resulting from housing damage.

INTERPRETATION

Informal socializing and social participation may prevent cognitive impairment following natural disaster.

FUNDING

National Institutes of Health (R01AG042463-04), the Japan Society for the Promotion of Science, the Japanese Ministry of Health, Labour and Welfare and the Japanese Ministry of Education, Culture, Sports, Science and Technology.