To identify the risks of the combination of normal body mass index (BMI) and central obesity (normal weight and central obesity (NWCO)) on physical activity and function.
Longitudinal Osteoarthritis Initiative Study.
Community based.
Adults aged 60 and older at risk of osteoarthritis (N = 2,210; mean age 68, range 67.1-69.0) were grouped according to BMI (normal 18.5-24.9 kg/m(2) , overweight 25.0-29.9 kg/m(2) , obese ≥30.0 kg/m(2) ). High waist circumference (WC) was defined as greater than 88 cm for women and greater than 102 cm for men. Subjects were subcategorized according to WC (five categories). Subjects with normal BMI and a large WC were considered to have NWCO (n = 280, 12.7%).
Six-year changes in the Physical Component Summary of the Medical Outcomes Study 12-item Short Form Survey (PCS), Physical Activity Scale for the Elderly (PASE), and Late-Life Function and Disability Index (LL-FDI) were examined. The association between BMI and WC over 6 years was assessed (reference normal BMI, normal WC). Stratified analyses were performed according to age (60-69; ≥70).
Physical component scores, PASE, and LL-FDI declined with time. Mean PASE scores at 6 years differed between the NWCO group and the group with normal BMI and WC (117.7 vs 141.5), but rate of change from baseline to 6 years was not significantly different (P = .35). In adjusted models, those with NWCO had greater decline in PCS over time, particularly those aged 70 and older than those with normal BMI and WC (time interaction β = -0.37, 95% confidence interval = -0.68 to -0.06).
Normal weight and central obesity in older adults at risk of osteoarthritis may be a risk factor for declining function and physical activity, particularly in those aged 70 and older, suggesting the value of targeting those with NWCO who would otherwise be labeled as low risk.