Weight loss from 20 years of age is associated with cognitive impairment in middle-aged and elderly individuals

BACKGROUND Few empirical studies have been conducted to identify modifiable factors that may affect cognitive impairment in Japanese individuals. The present study aimed to clarify whether body mass and lifestyle are associated with cognitive impairment in Japanese middle-aged and elderly individuals. METHODS Subjects were 1814 community-dwelling individuals aged 44-79 years, all of whom were participants of the Murakami Cohort Study baseline survey conducted in 2011-2013. Cognitive function was assessed using the Mini-Mental State Examination (MMSE) in 2014-2016, and cognitive impairment, the outcome measure, was defined as an MMSE score <24. Predictor variables were body mass index (BMI), long-term weight changes from 20 years of age, and lifestyle factors, such as smoking, drinking, and physical activity levels, which were obtained from a self-administered questionnaire in the baseline survey. Covariates were sex, age, education level, and histories of stroke and diabetes. Multiple logistic regression analysis was used to calculate the adjusted odds ratios (ORs). RESULTS The prevalence of overall cognitive impairment was 6.2%. The adjusted ORs of cognitive impairment in the lowest (<[-4]kg) (OR = 2.70, 95%CI, 1.18-6.20) and second ([-4]-[0]kg) (OR = 2.37, 95%CI, 1.04-5.37) quintiles for long-term weight change were significantly higher than the reference 4th quintile ([+4]-[+7]kg). The adjusted OR in the highest quintile (≥[+8]kg) was 2.24 (95%CI, 0.99-5.04). Current BMI was not associated with cognitive impairment. CONCLUSIONS Long-term weight loss is associated with cognitive impairment in Japanese middle-aged and elderly individuals. Because the present study was retrospective in nature, prospective studies should also be conducted for further characterization of this association.