Risk of Osteoporotic Fractures Among Obese Women Based on Body Mass Index and Waist Circumference: A Nationwide Cohort in South Korea

We evaluated the association between obesity status by body mass index (BMI) or waist circumference (WC) and osteoporotic fracture risk. We collected data of 143,673 women with a mean age of 58.5 years without history of osteoporotic fracture from the Korean National Health Insurance Service Cohort. Participants were divided into four groups according to obesity by BMI and WC, normal BMI/WC (BMI 18.5-24.9 kg/m and WC < 85 cm, reference), obese BMI/normal WC (BMI ≥ 25 kg/m and WC < 85 cm), normal BMI/obese WC (BMI < 25 kg/m and WC ≥ 85 cm), and obese BMI/WC (BMI ≥ 25 kg/m and WC < 85cm). Cox proportional hazards regression analyses were performed to obtain hazard ratios (HRs) with 95% confidence intervals (CIs) for the subsequent median 6.0 years, which were adjusted for age, socioeconomic status, lifestyle, morbidity index, and osteoporosis medication. Compared with the normal group, normal BMI/obese WC was associated with a higher osteoporotic fracture risk after multivariable adjustment (HRs [95% CI], 1.13 [1.05-1.21]), and obese BMI/normal WC was associated with a lower osteoporotic fracture risk (0.89 [0.84-0.94]). Obese BMI/normal WC was associated with a lower risk for hip fractures (0.75 [0.57-0.99]). Obese BMI/normal WC was associated with decreased risk of osteoporotic fracture, whereas normal BMI/obese WC was associated with increased risk of osteoporotic fracture compared with the normal group among East Asian women in their late 40s or more.