[Follow-up study of body mass index and risk of cognitive impairment among elderly adults aged ≥65 years old from longevity areas of China]

Objective: To discuss the relationship between body mass index (BMI) and cognitive impairment among elderly adults aged ≥65 years old from longevity areas of China. Methods: A total of 2 439 elderly adults from 8 longevity areas were included in our baseline survey by answering questionnaire and taking body measurements and blood biochemical examinations in 2012. In the follow-up study in 2014, we studied the cognitive impairment status among the 1 135 elderly adults aging ≥65 years old. Multivariate logistic regression model was used to analyze the relationship between BMI and cognitive impairment risk. Results: 113 participants were defined as cognitive impairment, with a positive rate at 10.0%. The positive rate in group of underweight, normal weight, and overweight and obese elderly were 22.2% (51/230), 7.5% (47/629), 5.4% (15/276). The rate of cognitive impairment in groups of low BMI (<19.7 kg/m(2)), middle BMI (19.7-23.1 kg/m(2)) and high BMI (>23.1 kg/m(2)) were separately 17.7% (66/372), 7.1% (27/379) and 5.2% (20/384) (P<0.001). Every 1.0 kg/m(2) increase in BMI, the risk of cognitive impairment would significantly decreased by 7% (RR(95%CI): 0.93(0.87-0.99)). Compared with participants with middle BMI level, the group of low BMI participants was associated with a significantly increased risk of cognitive impairment (RR (95% CI): 1.98(1.14-3.44)); while there was no significant association was observed in the high BMI group (RR(95%CI): 1.15(0.57-2.32)). Compared with elderly in normal weight, the elderly with under weight was in higher risk of cognitive impairment (RR (95%CI: 2.19(1.31-3.66)) and there was no significant association found between the elderly with overweight (RR(95%CI): 1.18(0.58-2.38)). Conclusion: Among the elderly ≥65 years old from longevity area, low BMI level and underweight were associated with the increased risk of cognitive impairment.