Association Between Adverse Childhood Experiences and Dementia in Older Japanese Adults.

Importance: The prevalence of dementia in Japan has been increasing. Childhood poverty has been associated with increased risk of cognitive impairment, possibly mediated by individuals' educational paths. However, the associations between dementia and adverse childhood experiences other than poverty and education have not been well documented. Objective: To examine the association between adverse childhood experiences and dementia onset among Japanese individuals born before 1948 who grew up during and after World War II. Design, Setting, and Participants: A 3-year (2013-2016) follow-up was performed of 17 412 participants in the Japan Gerontological Evaluation Study, a population-based cohort study of adults aged 65 years or older. Data were analyzed in December 2019. Main Outcomes and Measures: Dementia onset was assessed through the public long-term care insurance system. Adverse childhood experiences before the age of 18 years were assessed by survey at baseline. Seven adverse childhood experiences were assessed: parental death, parental divorce, parental mental illness, family violence, physical abuse, psychological neglect, and psychological abuse. Participants were classified according to whether they had 0, 1, 2, or 3 or more adverse childhood experiences. Cox regression models were used to estimate hazard ratios for the risk of dementia.
Results: Among 17 412 participants (9281 women [53.3%]; mean [SD] age, 73.5 [6.0] years), dementia occurred in 703 participants (312 men and 391 women) during a mean follow-up of 3.2 years (range, 2.4-3.3 years). Among all participants, 6804 (39.1%) were older than 75 years; 10 968 (63.0%) reported 0 adverse childhood experiences, 5129 (29.5%) reported 1 adverse childhood experience, 964 (5.5%) reported 2 adverse childhood experiences, and 351 (2.0%) reported 3 or more adverse childhood experiences. Participants who experienced 3 or more adverse childhood experiences had a greater risk of developing dementia compared with those who grew up without adverse childhood experiences, after adjustment for age, sex, childhood economic hardship, nutritional environment, and education (hazard ratio, 2.18; 95% CI, 1.42-3.35). After successive adjustment for adult sociodemographic characteristics, social relationships, health behavior, and health status, this hazard ratio was attenuated but remained statistically significant (1.78; 95% CI, 1.15-2.75; P = .009). Conclusions and Relevance: This study found that having 3 or more adverse childhood experiences was associated with increased dementia risk among older Japanese adults.