Nutritional predictors of cognitive impairment severity in demented elderly patients: The key role of BMI

The body mass index (BMI) is commonly used to assess nutritional status and the Mini Mental State Examination (MMSE) is a validated tool for assessing cognitive status in elderly people. Nutritional and cognitive aspects are closely related in dementia. To establish whether BMI predicts cognitive decline in demented patients and whether an "alarm" BMI cut-off exists for declining MMSE scores. 82 elderly demented patients underwent clinical, bio-chemical and functional assessment. Transversal study. The mean BMI was 26.08 +/- 4.48 kg/m(2) and the mean MMSE 18.68 +/- 5.38. Patients with BMI < 25 kg/m(2) had significantly lower MMSE scores (16.5 +/- 5.53 vs 20.38 +/- 4.64; p 0.001), fat-free mass (FFM; 27.76 +/- 8.99 vs 37.38 +/- 10.58 kg; p < 0.001), fat-free mass index (FFMI; 11.52 +/- 3.03 vs 14.67 +/- 2.89 kg/m(2); p < 0.001), and fat mass (FM; 24.90 +/- 6.89 vs 36.86 +/- 6.77 kg; p < 0.001), as well as lower Mini Nutritional Assessment (MNA) scores (23.80 +/- 2.50 vs 25.00 +/- 2.29; p=0.03) and higher vitamin B12 levels (460.95 +/- 289.80 vs 332.43 +/- 82.07 pg/ml; p=0.01). In the sample as a whole, MMSE scores significantly correlated with scores for MNA (r=0.27, p=0.01), FFM (r=0.27, p=0.01), BMI (r=0.19, p=0.05), ADL (r=0.28, p=0.01) and instrumental activities of daily living (IADL; r=0.34, p=0.002). On multiple logistic regression, BMI < 25 kg/m(2) was independently associated with the risk of moderate-severe cognitive impairment (OR=2.96; 95% CI; 1.16-7.55) and female gender was independently associated with severity of dementia (OR=3.14; 95% CI; 1.09-9.03). BMI seems to indicate global health status in elderly demented people and a BMI of 25 kg/m(2) can be considered an "alarm" cutoff, lower values coinciding with a worse cognitive status based on MMSE scores.