Citation

Hikichi H, Tsuboya T, Aida J, Matsuyama Y, Kondo K, Subramanian SV, Kawachi I. Lancet Planet. Health 2017; 1(6): e219.

Affiliation

Department of Social and Behavioral Sciences, Harvard T H Chan School of Public Health, Boston, MA, USA.

Copyright

(Copyright © 2017, Elsevier Publishing)

DOI

10.1016/S2542-5196(17)30098-0

PMID

29851606

Abstract

We thank Dr Ozaki and colleagues for their interest in our paper.1 Regarding loss of a loved one, we separately examined the effects of loss of relatives versus loss of friends on the decline in cognitive function. Neither type of loss was associated with cognitive decline. We note two limitations of our study. First, our survey asked about loss of “close relatives” in the disaster, and we could not distinguish between spouses and other close relatives (such as adult children). Second, we did not inquire on the baseline survey (ie, before the disaster) about the frequency of social interactions between the survivors and the relatives or friends who were lost. In some instances, the frequency of social interactions might have been quite intense (eg, daily), in which case their loss could have contributed more to the risk of cognitive decline.

Regarding potential gender differences, we fitted a three-way interaction term for housing damage × social capital × gender, and found that it was significant (p<0·001). In further gender-stratified analysis, we found that informal socialising and social participation appeared to significantly mitigate the effect of housing damage on cognitive decline in both sexes, but the effect was roughly twice as strong among women (coefficient −0·10, 95% CI −0·13 to −0·08, for females; coefficient −0·04, 95% CI −0·07 to −0·01, for males).

Regarding changes in living arrangement after the disaster, we checked the effect of changes in cohabiting with children. A change in living arrangement (ie, not living with children pre-disaster and living with children post-disaster) was adversely associated with cognitive function in women (coefficient 0·08, 95% CI 0·01 to 0·16), but not in men (coefficient −0·01, 95% CI −0·08 to 0·06). However, we believe those association reflects simultaneity bias—ie, changes in living arrangement triggered by a deterioration in cognitive function. The causal effect of changes in household composition might be difficult to identify because of this type of bias.

The Iwanuma city area was fortunately not affected by the radiation fallout from the Fukushima nuclear plant disaster. Thus, most of the survivors chose to stay, or relocated within the same city after the disaster. Indeed, the census population ...

Language: en