Associations of abdominal adiposity, lean body mass, and fat body mass with dementia and cognitive change in older age

INTRODUCTION: This study examined whether the waist circumference–body mass index ratio (WBR), lean body mass (LBM), and fat body mass (FBM) were associated with dementia or cognitive change. METHODS: We analyzed data from >17,000 individuals aged 65 to 98 years at enrollment. LBM and FBM were estimated using the Hume equation. Dementia was determined according to DSM-IV. Global cognition, verbal fluency, episodic memory, and psychomotor speed were assessed across 11 years. Cox and mixed-effects models were used to examine the associations with dementia and cognitive change. RESULTS: WBR was positively associated with dementia (Q4 versus Q1, hazard ratio [HR]: 1.29, p = 0.004) and cognitive decline (coefficients:−0.122 to −0.025, p < 0.05). Dementia risk was 15% to 38% lower for individuals in higher quartiles of LBM and FBM (Q2 to Q4), compared to Q1 (p < 0.05). Higher LBM and FBM were associated with slower cognitive decline (coefficients: 0.035 to 0.203, p < 0.05), except for verbal fluency. DISCUSSION: Higher LBM and FBM in later life may be associated with better cognition, while abdominal fat could be a risk factor. Highligths: Higher WBR is associated with greater dementia risk, only in men. Higher WBR is associated with faster cognitive decline. Greater LBM and FBM are associated with lower dementia risk. Greater LBM and FBM are associated with slower cognitive decline. Central adiposity may be a risk factor for cognitive impairment in older adults.