Community-level Educational Attainment and Dementia: A 6-year Longitudinal Multilevel Study in Japan

Abstract

Background:Understanding of the association between community-level socioeconomic status and dementia is insufficient. We examined the contextual effect of community-level prevalence of lower educational attainment on the risk of dementia incidence. This work further explored the potential differences in associations for urban and non-urban areas. Methods:We analyzed a six-year prospective cohort data from the Japan Gerontological Evaluation Study, a nationwide survey between 2010 and 2012 of 49,888 (23,339 men and 26,549 women) physically and cognitively independent individuals aged ≥65 years from 346 communities at 16 municipalities in seven prefectures. Dementia incidence was assessed through the public long-term care insurance system by the Ministry of Health, Labor, and Welfare in Japan. Educational years were dichotomized as ≤9 years and ≥10 years. We classified urban and non-urban areas using a Functional Urban Area defined by the European Union (EU) and Organisation for Economic Co-operation and Development (OECD). We performed a two-level (community- and individual-level) multilevel survival analysis to calculate hazard ratios (HRs) and 95% confidence intervals (CIs). Results:The cumulative incidence of dementia during the follow-up period was 10.3%. The mean proportion of educational attainment with ≤9 years was 41.1% (range, 4.7%–88.4%). Higher prevalence of community-level lower educational attainment had a significant association with a higher risk of dementia incidence (HR, 1.03; 95% CI, 1.00–1.06, estimated by 10 percentage points of lower educational attainment) post adjusting for individual-level educational years, age, sex, income, residential years, disease, alcohol, smoking, social isolation, and population density. The association was significant in non-urban areas (HR, 1.05; 95% CI, 1.00–1.10). Conclusions:Older people living in communities with a higher prevalence of less educational attainment among their age demographic tended to develop dementia more often than those living in areas with a lower prevalence of less educational attainment after adjusting for individual-level educational attainment and covariates. In particular, the association was more pronounced in non-urban areas than in urban areas. Securing education for adolescence as a life course and population approach could thus be crucial to prevent dementia later in life among all older people living in non-urban areas.