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

Abstract

Introduction: 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.

Objectives: To establish whether BMI predicts cognitive decline in demented patients and whether an "alarm" BMI cut-off exists for declining MMSE scores.

Subjects and methods: 82 elderly demented patients underwent clinical, bio-chemical and functional assessment.

Design: Transversal study.

Results: The mean BMI was 26.08±4.48 kg/m² and the mean MMSE 18.68±5.38. Patients with BMI<25 kg/m² 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/m²; 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/m² 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).

Conclusion: BMI seems to indicate global health status in elderly demented people and a BMI of 25 kg/m² can be considered an "alarm" cut-off, lower values coinciding with a worse cognitive status based on MMSE scores.