Body mass index predicts progression of mild cognitive impairment to dementia

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