Body mass index and cognitive function in community-living elderly men and women: The Tromsø Study

Abstract

<p><i>Background:</i> Previous studies have reported conflicting results regarding the relationship between cognitive function and nutritional status in the elderly. The primary objective of this study was to investigate the associations between body mass index (BMI) and cognitive function in a sample of community-living elderly men and women. <p><i>Methods:</i> This population-based study comprised data from 1148 men and 1344 women aged 65 years or older from the municipality of Tromsø, Norway. The data was collected from the 5th survey of the Tromsø Study. A cross-sectional design was used to examine the associations between nutritional status and cognitive function. BMI was categorized into six groups (≤19.99, 20.00-22.49, 22.50-24.99, 25.00-27.49, 27.50-29.99 and ≥30 kg/m2). Cognitive function was measured by use of the 12-word test, part one (immediate recall) and part two (short-term delayed recall), the digit symbol coding test, and the finger tapping test with dominant and non-dominant hand. The statistical associations between BMI and cognitive function were assessed using multiple logistic regression models. The data was adjusted for age, sex, educational level, co-morbidity, alcohol use and smoking habits, factors known to be associated with both BMI and cognitive function. <p><i>Results:</i> A BMI ≥30 kg/m2 was associated with a reduced score on the finger tapping test in the non-dominant hand (OR: 1.53, 95% CI: 1.11-2.10, p= 0.009). A BMI of ≤22.49 kg/m2 was associated with a reduced score on the short-term delayed recall test (OR: 1.54, 95% CI: 1.07-2.23, p=0.020). For the other BMI categories and cognitive test scores there were no significant associations. <p><i>Conclusion:</i> Overall, there were no statistically significant associations between underweight, overweight or obesity and cognitive function in this study, also when adjusting for age, sex and confounding factors. An obese subgroup showed reduced performance on the finger tapping test, whereas an underweight subgroup performed poorer on the short-term delayed recall test.