[Intra-household isolation and psychological health among community-dwelling middle-aged and older adults: A cross-sectional analysis from the Wako Cohort Study].

Objective Traditionally, families and households have served as stable sources of support and the primary settings of daily life; however, their roles have changed significantly in recent years. This study defined "intra-household isolation" as a state in which individuals live with family members or housemates yet experience markedly limited interactions within the household. We examined the association between intra-household isolation and psychological health among community-dwelling middle-aged and older adults.Methods Data were collected through a mail-in questionnaire as part of the baseline survey of the Wako Cohort Study conducted in 2023, targeting the residents of Wako City, Saitama Prefecture. The mail-in questionnaire comprised two separate surveys for individuals aged 40-64 years and those aged ≥65 years, yielding 2,395 and 6,429 valid responses, respectively, for a total of 8,824 responses. Intra-household isolation was defined as cohabitation with others but spending ＜15 minutes daily conversing with them and being alone at home for most of the time on weekdays, weekends, and holidays. Psychological health outcomes included self-rated health, depression, well-being, and loneliness. We conducted modified Poisson regression and multiple regression analyses, adjusting for demographic factors, socioeconomic status, health behaviors, health status, and social networks outside the household.Results Among the respondents, 44.7% were male, and the average age was 70.0 years (standard deviation: 12.7). The prevalence of intra-household isolation was 4.7% for all participants (3.2% in those aged 40-64 years and 5.3% in those aged ≥65 years) and 5.8% for cohabiting participants (3.7% in those aged 40-64 years and 6.7% in those aged ≥65 years). The proportion of intra-household isolation was higher in the older age group, and across nearly all age groups, men were more likely to experience intra-household isolation than women. Multivariate analyses revealed that, even after adjusting for social networks outside the household and other covariates, individuals experiencing intra-household isolation had poorer self-rated health, greater depression, lower well-being, and stronger feelings of loneliness than those who lived alone or were not isolated within the household. After examining the interaction terms, we found that the association between intra-household isolation and depression was strong among individuals aged ≥65 years. In contrast, this association was weak among those with strong neighborhood ties and those who frequently interacted with non-cohabiting individuals.Conclusion The findings suggest that even when cohabiting with others, limited interactions within a household may increase the risk of psychological health deterioration. It is essential to carefully assess not only social interactions outside the household, but also isolation within it.