A higher body mass index is linked to faster cognitive decline in older adults, indicating BMI could be a modifiable risk factor for brain aging.

The strongest link appears in the eighth year of the study and is more pronounced among participants over 65.

Current obesity estimates show about two in five Americans meet BMI-based obesity criteria, and broadening the definition to include waist size and related conditions could raise the prevalence to roughly 75%.

There are no cures for dementia, making the identification of modifiable risk factors essential to prevent or delay onset.

Researchers stress that mitigating modifiable risks is crucial given the absence of a dementia cure.

More than 7 million Americans live with dementia, with projections suggesting the number could double by 2050.

Dementia prevalence in the United States exceeds 7 million and is expected to double by mid-century, highlighting the importance of addressing modifiable factors like BMI.

Source study: Xu et al., 2026, in the Journal of Neurology, titled “Association between cumulative average BMI and cognitive decline: a 24-year cohort study.”

Reference: Xu Q et al., 2026, Journal of Neurology, DOI 10.1007/s00415-026-13696-2.