Body Mass Index and Cognitive Health in Aging Populations

Body mass index (BMI), a widely used indicator of relative weight, shows complex associations with cognitive health across the life course. Midlife overweight and obesity have been linked to elevated risk of subsequent cognitive decline and dementia, often through vascular injury, metabolic dysfunction and chronic inflammation. In contrast, low or declining BMI in later life frequently heralds preclinical neurodegenerative processes and accelerated loss of neuronal integrity. Life-course trajectories reveal that cumulative exposure to excess bodyweight from adolescence through midlife may exert subtle effects on later cognitive performance, although early-life factors such as baseline cognition and socioeconomic conditions can confound these relationships. Neuroimaging and biomarker studies suggest divergent pathways: adiposity-related vascular changes may amplify amyloid-β accumulation and tau pathology, while unintentional weight loss in older adults often reflects evolving tau-mediated neurodegeneration. Globally, these insights emphasise the need for age-specific weight management strategies, targeting midlife prevention of obesity-related cerebrovascular damage, alongside monitoring of unintentional weight loss in the elderly as an early warning of cognitive decline.

Research from Nature Portfolio

A cross-sectional analysis of asymptomatic carriers of autosomal dominant Alzheimer’s mutations demonstrated that reductions in BMI begin almost two decades before expected clinical onset. Lower BMI correlated with higher cerebral amyloid-β burden and poorer episodic memory performance, suggesting that weight loss may be an early systemic sign of underlying neuropathology. These findings underscore a temporal window in which metabolic changes parallel accumulating Alzheimer’s-related pathology and point to weight trajectories as a potential biomarker of preclinical disease.

Body Mass Index and Cognitive Health in Aging Populations publication trend

The graph below shows the total number of articles in body mass index and cognitive health in aging populations across all publications each year (not limited to Nature Index journals).

Technical terms

Body Mass Index (BMI): A ratio of weight to height squared used to classify underweight, normal weight, overweight and obesity.

Dementia: A clinical syndrome characterised by progressive decline in memory, reasoning and other cognitive functions severe enough to interfere with daily life.

Amyloid-β (Aβ): A protein fragment that accumulates in the brain and forms plaques, a hallmark of Alzheimer’s disease pathology.

Tau deposition: The accumulation of tau protein tangles in the brain, another key feature of Alzheimer’s disease linked to neuronal dysfunction.

Metabolically healthy obesity (MHO): A condition in which individuals have a BMI in the obese range but lack the metabolic abnormalities typically associated with obesity.

References

1. Decreased body mass index in the preclinical stage of autosomal dominant Alzheimer’s disease. Scientific Reports (2017).
2. Early-life cumulative exposure to excess bodyweight and midlife cognitive function: longitudinal analysis in three British birth cohorts. The Lancet Healthy Longevity (2024).
3. Is metabolic-healthy obesity associated with risk of dementia? An age-stratified analysis of the Whitehall II cohort study. BMC Medicine (2023).
4. Body mass index and two-year change of in vivo Alzheimer’s disease pathologies in cognitively normal older adults. Alzheimer's Research & Therapy (2023).