Background Obesity, commonly defined as body mass index (BMI) >30, is a key modifiable risk factor for dementia. However, evidence on the relationships of adiposity measures and sarcopenia with cognitive impairments in older populations is largely conflicting. Moreover, research on relative adiposity measures and cognitive functioning is scarce. We aimed to examine whether obesity, fat mass (FM), sarcopenia and regional deposition of adipose tissue are associated with impaired cognitive functioning in a representative sample of older British men.

Methods Data are based on the British Regional Heart Study, a cohort study across 24 British towns initiated in 1978–80. In 2010–12, 1,570 participants aged 71–92 years were examined (55% response rate). Cognitive functioning was based on the Test-Your-Memory cognitive screening tool. Adiposity measures included central FM (CFM), peripheral FM (PFM), visceral FM (VFM) and total FM (TFM). Sarcopenia was defined using the Foundation for the National Institutes of Health criteria, including low appendicular muscle mass, gait speed and grip strength.

Results Among 1,570 men, 636 (41%) were classified in the mild cognitive impairment (MCI) and 133 (8%) in the Alzheimer’s disease (AD) range of cognitive functioning. Multinomial logistic regressions showed that compared to individuals in the normal cognitive ageing group, those in the AD range of cognitive functioning were significantly more likely to be in the upper quintiles of CFM, PFM, VFM and TFM, to have a BMI >30, waist circumference >102 cm and to be sarcopenic. After adjusting for insulin-resistance (IR), C-reactive protein (CRP) and interleukin-6 (IL-6), BMI (RR = 1.99, 95% CI 1.22–3.25), PFM (RR = 2.16, 1.27–3.65), VFM (RR = 1.98, 95% CI 1.15–3.41) and total FM (RR = 1.79, 95% CI 1.05–3.04) all remained significantly associated with AD range of cognitive functioning. VFM and sarcopenia were the only body composition characteristics associated with MCI, and these relationships remained significant after adjustments for IR, CRP and IL-6 (RR = 1.76, 95% CI 1.19–2.60 and RR = 1.54, 95% CI 1.09–2.16, respectively). Of the relative adiposity measures, PFM/CFM showed the strongest association with both mild and severe cognitive impairments (RR = 1.64, 95% CI 1.23–2.18 and RR = 3.07, 95% CI 1.95–4.82, respectively), while CFM/FM was inversely associated with AD range of cognitive functioning (RR = 0.49, 95% CI 0.27–0.88).

Conclusion This study highlights unique body composition characteristics including regional adiposity deposition and sarcopenia, which are associated with cognitive impairments in a representative sample of older British men. The results suggest that targeted public health interventions aiming to reduce regional adiposity and muscle loss in older people could reduce the risk of cognitive impairment.