Studies over the past decade have made it clear that waist circumference is a better measure of the degree of harm resulting from excess fat tissue than body mass index. It is the visceral fat tissue packed around abdominal organs that is the harmful form of fat, when present in excessive amounts. It is metabolically active, promoting chronic inflammation and a greater burden of senescent cells. Thus any measure of fat in the abdomen is likely going to have a better correlation with age-related disease and mortality than a more global measure of fat throughout the body.
Obesity in midlife is a modifiable risk factor for dementia; however, in later life, a higher body mass index (BMI) has a protective effect. This discordance in findings might be due to the reverse causation of weight loss beginning approximately 10 years before the onset of dementia. It is also possible that BMI does not adequately reflect nutritional status (degree of obesity or weight loss) in later life. This discrepancy arises because older adults usually experience changes in body composition in which fat mass increases and fat-free mass decreases with age, although the change in BMI is small.
In this context, recent studies have measured abdominal adiposity using waist circumference (WC) and waist-hip ratio, but not BMI, to assess nutritional status. Higher WC and waist-hip ratio are associated with the development of dementia and brain structural changes, such as hippocampal atrophy and white matter hyperintensity, in later life. Based on the results of these studies, the accumulation of abdominal adiposity may have an adverse effect on brain health in later life.
This study investigated the association between abdominal adiposity at baseline and change in cognitive function in community-dwelling older adults using longitudinal data collected separately for men and women over 10 years. Cognitive function was evaluated biennially using the Mini-Mental State Examination (MMSE) over 10 years. Waist circumference (WC) was measured at the naval level, and subcutaneous fat area (SFA) and visceral fat area (VFA) were assessed using baseline computed tomography scans.
This study included 873 older adults. In men, the groups with the highest levels of WC, SFA, and VFA exhibited a greater decline in MMSE score than the groups with the lowest levels, with standardized coefficient β: WC, -0.12; SFA, -0.13; VFA, -0.11. In women, the group with the highest level of WC and SFA showed a greater decline in MMSE score than the group with the lowest level, with β: WC, -0.12; SFA, -0.18), but VFA was not associated with cognitive decline.
Link: https://doi.org/10.1...nha.2024.100175
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