Body Mass Index Predicts Progression of Mild Cognitive Impairment to Dementia

To examine the relationship between body mass index (BMI) and progression to dementia and Alzheimer's disease (AD) in mild cognitive impairment (MCI).

Two hundred and twenty-eight MCI subjects (mean age 74.04 ± 6.94 years; 57% female) from a memory clinic were followed for 2.40 ± 1.58 years. Baseline height and weight were used to calculate the BMI. The main outcome was progression to dementia (DSM-IV criteria) and AD (NINCDS-ADRDA criteria). Cox proportional hazard models were used to assess the longitudinal association of BMI with dementia and AD, adjusting for a comprehensive set of covariates, including vascular risk factors/diseases and neuroimaging profiles.

Out of 228 subjects with MCI, 117 (51.3%) progressed to dementia. Eighty-nine (76%) of the incident dementia cases had AD. In both unadjusted and multi-adjusted models, a higher BMI was associated with a reduced risk of dementia (multi-adjusted HR 0.9; 95% CI 0.8-0.9) and AD (multi-adjusted HR 0.9; 95% CI 0.8-0.9). Being underweight increased the risk of all types of dementia (multi-adjusted HR 2.5; 95% CI 1.2-5.1) but was not specifically associated with AD (multi-adjusted HR 2.2; 95% CI 0.9-5.3).

BMI predicted progression of MCI to dementia and AD. In particular, a higher BMI was associated with a lower risk of dementia and AD, and underweight was associated with a higher risk of dementia. BMI assessment may improve the prognostic accuracy of MCI in clinical practice.