Effect of the 2018 Japan floods and COVID-19 pandemic on cognitive decline among atomic bomb survivors in Hiroshima, Japan: a retrospective cohort study.

BACKGROUND

Atomic bomb survivors (ABSs) in Hiroshima are facing climate change-related natural disasters and emerging infectious diseases. The cognitive function of aging ABSs is vulnerable to the inevitable environmental changes caused by the 2018 Japan floods and COVID-19 pandemic.

AIMS

This study examined the effects of these two disastrous events on cognitive function.

METHODS

This retrospective cohort study included all verified individuals utilizing Long-Term Care Insurance services in Hiroshima Prefecture. The observation period was from January 2018 to December 2022. The participants were divided into three groups: ABSs, welfare recipients (WRs), and others. The objective variable was moderate or severe cognitive deterioration. We performed a difference-in-differences analysis using logistic regression models to investigate the effect of the two disastrous events on cognitive function compared with the effect of the other groups.

RESULTS

There were 184,252 participants, including 16,306 ABSs (8.8%) and 8,509 WRs (4.6%). The difference-in-differences analysis showed no statistically significant effect of the 2018 Japan floods. The analysis also revealed that moderate cognitive decline among ABSs and WRs decreased during the COVID-19 pandemic (2020, 2021, and 2022). Moreover, severe cognitive decline among ABSs decreased after the onset of the COVID-19 pandemic (2020 and 2021).

DISCUSSION

Although many older adults experienced cognitive exacerbations during the COVID-19 pandemic, ABSs had a lower risk of cognitive decline than those of non-WRs. However, no significant changes were observed during the 2018 Japan floods.

CONCLUSIONS

ABSs had a reduced risk of cognitive decline during the pandemic compared with that of the other groups.