Waist Circumference and Domain-Specific Cognitive Function Among Non-Demented Japanese Older Adults Stratified by Sex: Results from the Takashima Cognition Study

BACKGROUND: While being obese in mid-life is associated with an increased risk of dementia and cognitive decline in late-life, being obese in late-life is shown to be associated with a lower risk of these outcomes in some studies. This phenomenon is known as the "obesity paradox", but the underlying reasons and potential sex difference have not been well understood. OBJECTIVE: To investigate the association between cognition and waist circumference (WC), an alternative measure of body fat which can be measured easier than body mass index (BMI), among older adults in each generation of late-life for men and women separately. METHODS: Three hundred thirty-five participants were used in the current study who were identified by random sampling of residents aged 65-74, 75-84, and 85 + years in Takashima County, Shiga Prefecture, Japan during 2005-2006. Associations between WC and domain-specific cognitive functions measured by 12 neuropsychological tests were examined using multivariable linear regression models with covariates: age, education, and hypertension. RESULTS: Larger WC was associated with better attention/working memory among 65-74-year old women and with better learning/acquisition among 65-74-year-old men, while larger WC was associated with worse learning/acquisition, memory, attention/working memory, and language/fluency among 75-84-year old men. CONCLUSION: We found age and sex differences in the association between WC and domain-specific cognitive functions. Among older old men (age 75-84), larger WC had negative effects on various domains including memory, attention, language, and executive functions, while we did not find any negative effects of larger WC on cognition among women in any age groups.