Carried out by researchers from Trinity College, Dublin, the University of Ulster, and St James’s Hospital, the new study looked at data taken from 5,186 adults over the age of 60 participating in the Trinity Ulster Department of Agriculture (TUDA) aging cohort study, which has gathered data from thousands of elderly adults in Northern Ireland and Ireland.

The participants completed neuropsychological assessments, and their body mass index (BMI) and waist-to-hip ratio were also recorded.

The team found that a higher waist-hip ratio was associated with a reduced cognitive function, which it said may be explained by an increased secretion of inflammatory markers by belly fat, which has been previously associated with a higher risk of impaired cognition.

In contrast, BMI appeared to have a protective effect on cognitive function. Though the BMI does not differentiate between fat and muscle, the researchers said they believed that the protective factor is likely to be the muscle component.

Previous studies have found that people who are overweight perform worse on tests of memory and visuospatial ability, compared to those who are of normal weight, although data on whether this is also true for older adults is lacking. The authors noted that, to the best of their knowledge, this is one of the largest studies of older adults to report these findings.

Senior study author Conal Cunningham commented, “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.”

The global prevalence of dementia is predicted to increase from 24.3 million in 2001 to 81.1 million by 2040.