Social isolation and self-reported cognitive decline among older adults in Japan: A longitudinal study in the COVID-19 pandemic

Abstract Objectives We aimed to examine the association between the transition to social isolation and cognitive decline in older adults during the coronavirus disease 2019 (COVID-19) pandemic. Design Longitudinal study. Setting and Participants The study included participants from a community in a semiurban area of Japan. We conducted a mailed questionnaire survey of 2000 noninstitutionalized older adults who were randomly sampled. Of those who completed both the baseline and follow-up surveys in March and October 2020, respectively, participants aged ≥70 years without cognitive impairment at baseline were included in the analysis. Methods Participants were classified into 4 groups based on their baseline and follow-up social isolation status, which were as follows: “remained nonisolated,” “isolated from nonisolation,” “nonisolated from isolation,” and “consistent isolation.” Self-reported cognitive function was assessed using the Cognitive Performance Scale, and level 2 (mild impairment) or higher (moderate to severe impairment) was defined as cognitive impairment. Results Ultimately, 955 older adults were analyzed. The mean age of the participants was 79.6 years (standard deviation = 4.7) and 54.7% were women. During the follow-up period, 54 (5.7%) participants developed cognitive impairment. Multivariable logistic regression analysis revealed that compared with the group that remained nonisolated, the isolated from nonisolation and consistent isolation groups were significantly associated with the onset of cognitive impairment [isolated from nonisolation: odds ratio (OR) = 2.74, 95% confidence interval (CI) = 1.13-6.61, P = .026; consistent isolation: OR = 2.33, 95% CI = 1.07-5.05, P = .033]. Conclusions and Implications Social isolation during the COVID-19 pandemic was associated with a decline in cognitive function among older adults. Attention to the social isolation process during the pandemic may be necessary to protect older adults’ cognitive health.