A large Irish study found that higher belly fat was associated with reduced cognitive function in older adults.
The study by researchers at Trinity College Dublin, using data from over 5,000 individuals, has found that a measure of belly fat (waist:hip ratio) was associated with reduced cognitive function in older Irish adults (>60 years of age). These findings have significant implications as the global prevalence of dementia is predicted to increase from 24.3m in 2001 to 81.1m by 2040.
Previous studies have found that people who are overweight do not perform as well on tests of memory and visuospatial ability compared to those who are normal weight. However, it is not well known if this is true in older adults. This is of concern within Ireland, as over half of the over 50s population is classified as being centrally obese, with only 16% of men and 26% of women reported to have a BMI (body mass index) within the normal range.
The researchers used data from the Trinity Ulster Department of Agriculture (TUDA) ageing cohort study comprising, which is a cross-border collaborative research project gathering data from thousands of elderly adults in Northern Ireland and Ireland.
The researchers found that a higher waist:hip ratio was associated with reduced cognitive function. This could be explained by an increased secretion of inflammatory markers by belly fat, which has been previously associated with a higher risk of impaired cognition. On the contrary, body mass index (BMI) was found to protect cognitive function. BMI is a crude measure of body fat and cannot differentiate between fat and fat-free mass (muscle), thus it is proposed that the fat-free mass component is likely to be the protective factor.
To the best of the authors’ knowledge, this is one of the largest studies of older adults to report these findings. Given the high prevalence of overweight and obesity in the older population and the economic and social burden of cognitive dysfunction, the results suggest that reducing obesity and exposure to obeso-genic risk factors could offer a cost-effective public health strategy for the prevention of cognitive decline.
Clinical associate professor in medical gerontology at Trinity, Conal Cunningham, is the senior author of the study. He said: “While we have known for some time that obesity is associated with negative health consequences our study adds to emerging evidence suggesting that obesity and where we deposit our excess weight could influence our brain health. This has significant public health implications.”
Previous reports investigating adiposity and cognitive function in the population allude to a negative association, although the relationship in older adults is unclear. The aim of this study was to investigate the association of adiposity (BMI and waist:hip ratio (WHR)) with cognitive function in community-dwelling older adults (≥60 years). Participants included 5186 adults from the Trinity Ulster Department of Agriculture ageing cohort study. Neuropsychological assessment measures included the Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB) and Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Multi-variable linear regression models were used to assess the association between adiposity and cognitive function adjusting for insulin resistance, inflammation and cerebrovascular disease. The mean ages were 80·3 (SD 6·7), 71·0 (SD 7·3) and 70·2 (SD 6·3) years on the cognitive, bone and hypertensive cohorts, respectively. In the cognitive cohort, BMI was positively associated with immediate and delay memory, visuospatial/constructional ability, language and MMSE, and negatively with FAB (log-transformed), whereas WHR was negatively associated with attention. In the bone cohort, BMI was not associated with any cognitive domain, whereas WHR was negatively associated with visuospatial/constructional ability, attention and MMSE. In the hypertensive cohort, BMI was not associated with any cognitive domain, whereas WHR was negatively associated with immediate and delayed memory, visuospatial/constructional ability, language and MMSE and positively with FAB (log-transformed). In the cognitive and bone cohorts, the association of WHR and attention disappeared by further controlling for C-reactive protein and HbA1C. In this study of older adults, central adiposity was a stronger predictor of poor cognitive performance than BMI. Older adults could benefit from targeted public health strategies aimed at reducing obesity and obeseogenic risk factors to avoid/prevent/slow cognitive dysfunction.
Ontefetse Ntlholang, Kevin McCarroll, Eamon Laird, Anne M Molloy, Mary Ward, Helene McNulty, Leane Hoey, Catherine F Hughes, JJ Strain, Miriam Casey, Conal Cunningham