[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]
Increased risk of dementia in the aftermath of the 2011 Great East Japan Earthquake and Tsunami
Hiroyuki Hikichi a,1, Jun Aida b, Katsunori Kondo c,d, Toru Tsuboya b, Yusuke Matsuyama b, S. V. Subramanian a, and Ichiro Kawachi a
Author Affiliations: a Department of Social and Behavioral Sciences, Harvard T. H. Chan School of Public Health, Boston, MA 02115; b Department of International and Community Oral Health, Tohoku University Graduate School of Dentistry, Sendai, Miyagi 980-8575, Japan; c Center for Preventive Medical Sciences, Chiba University, Chiba-shi, Chiba 260-8670, Japan; d Center for Gerontology and Social Science, National Center for Geriatrics and Gerontology, Obu, Aichi 474-8511, Japan
Edited by Susan T. Fiske, Princeton University, Princeton, NJ, and approved September 16, 2016 (received for review May 15, 2016)
Recovery after major disaster poses potential risks of dementia for the elderly population. However, no previous studies have examined exposure to natural disaster and changes in risk factors as predictors of deterioration in cognitive function. We prospectively examined whether housing damage and loss of relatives or friends were associated with cognitive decline in the aftermath of the 2011 Great East Japan Earthquake and Tsunami. In this study, which included 3,566 survivors who are 65 y old or older, the severity of housing damage was significantly associated with cognitive decline after controlling changes of covariates and risk factors during the follow-up period. The cognitive decline should be listed as a health risk of older survivors in the aftermath of natural disasters.
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.
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Author contributions: H.H. and I.K. designed research; H.H., J.A., K.K., T.T., Y.M., S.V.S., and I.K. performed research; H.H. analyzed data; and H.H., J.A., K.K., T.T., Y.M., S.V.S., and I.K. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at http://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1607793113/-/DCSupplemental.
Keywords: Japan; Dementia; Mass Casualty Events; Earthquakes; Tsunami.