Normal Weight with Central Obesity, Physical Activity, and Functional Decline: Data from the Osteoarthritis Initiative

ObjectivesTo 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. DesignLongitudinal Osteoarthritis Initiative Study. SettingCommunity based. ParticipantsAdults 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 18.5-24.9kg/m(2), overweight 25.0-29.9kg/m(2), obese 30.0kg/m(2)). High waist circumference (WC) was defined as greater than 88cm for women and greater than 102cm 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%). MeasurementsSix-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 6years was assessed (reference normal BMI, normal WC). Stratified analyses were performed according to age (60-69; 70). ResultsPhysical component scores, PASE, and LL-FDI declined with time. Mean PASE scores at 6years 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 6years 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 =-0.37, 95% confidence interval=-0.68 to -0.06). ConclusionNormal 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.