Associations of fat and muscle tissue with cognitive status in older adults: the AGES-Reykjavik Study.

ABSTRACT

Background/Objective: studies on the association of dementia with specific body composition (BC) components are scarce. Our aim was to investigate associations of BC measures with different levels of cognitive function in late-life. Methods: we studied 5,169 participants (mean age 76 years, 42.9% men) in the AGES-Reykjavik Study of whom 485 (9.4%) were diagnosed with mild cognitive impairment (MCI) and 307 (5.9%) with dementia. Visceral fat, abdominal and thigh subcutaneous fat, and thigh muscle were assessed by computed tomography. MCI and dementia were based on clinical assessment and a consensus meeting; those without MCI or dementia were categorised as normal. Multinomial regression models assessed the associations stratified by sex and in additional analyses by midlife body mass index (BMI). Results: among women, there was a decreased likelihood of dementia per SD increase in abdominal subcutaneous fat (OR 0.72; 95% CI 0.59-0.88), thigh subcutaneous fat (0.81; 0.67-0.98) and thigh muscle (0.63; 0.52-0.76), but not visceral fat, adjusting for demographics, vascular risk factors, stroke and depression. Inverse associations of fat with dementia were attenuated by weight change from midlife and were strongest in women with midlife BMI <25. In men, one SD increase in thigh muscle was associated with a decreased likelihood of dementia (0.75; 0.61-0.92). BC was not associated with MCI in men or women. Conclusion: a higher amount of abdominal and thigh subcutaneous fat were associated with a lower likelihood of dementia in women only, while more thigh muscle was associated with a lower likelihood of dementia in men and women.