The relationship between body mass index and self-reported functional limitation among older adults: A gender difference

OBJECTIVES: To determine whether there is a gender difference in how body m ass index (BMI) relates to self-reported functional limitation. Also, to ev aluate whether the method of categorizing BMI changes the observed results. DESIGN: Cross-sectional cohort study. SETTING: Rural Pennsylvania. PARTICIPANTS: A total of 7,120 male (n = 3,312) and female (n = 3,808) comm unity-dwelling older adults enrolled in a Medicare managed-risk contract. MEASUREMENTS: All subjects completed a modified Level II Nutrition Risk Scr een upon enrollment in the health plan. Height and weight were obtained by nursing personnel during an enrollment clinic visit. Subjects who reported 10 or more pounds weight loss in the previous 6 months were excluded. Logis tic regression was used to evaluate the relationship between BMI and self-r eported functional limitation separately for each sex, adjusting for age, d epression, and polypharmacy. Two schemes were used to categorize BMI: equal ly distributed sex-specific quintiles and arbitrary division based on Natio nal Institutes of Health (NIH) Obesity Guidelines. RESULTS: How BMI relates to functional limitation depends upon both sex and method of categorizing BMI. When BMI was considered in gender-specific qui ntiles, women in the highest quintile of BMI had increased risk of function al impairment; there was no relationship between BMI and functional limitat ion for men. When BMI was categorized by the NPH obesity guidelines, both m en and women with BMI >40 had significantly increased risk of functional li mitation. CONCLUSIONS: The mechanisms behind gender discrepancy in self-reported func tional limitation remain unclear. Studies may need to consider men and wome n separately, because how BMI relates to function depends on gender. Furthe r research is needed to evaluate how changes in weight and body composition during middle and old age affect functional status.