Women with severe obesity and relatively low bone mineral density have increased fracture risk

Among women with obesity, those with the lowest bone density have the highest fracture risk. The types of fractures include any fracture, fragility-type fractures (vertebra, hip, upper arm, forearm, and lower leg), hand and foot fractures, osteoporotic, and other fracture types.

Recent reports have contradicted the traditional view that obesity is protective against fracture. In this study, we have evaluated the relationship between fracture history and bone mineral density (BMD) in subjects with obesity.

Fracture risk was assessed in 400 obese women in relation to body mass index (BMI), BMD, and clinical and laboratory variables.

Subjects (mean age, 43.8 years; SD, 11.1 years) had a mean BMI of 46.0 kg/m(2) (SD, 7.4 kg/m(2)). There were a total of 178 self-reported fractures in 87 individuals (21.8% of subjects); fragility-type fractures (hip, vertebra, proximal humerus, distal forearm, and ankle/lower leg) were present in 58 (14.5%). There were higher proportions of women in the lowest femoral neck BMD quintile who had any fracture history (41.3 vs. 17.2%, p < 0.0001), any fragility-type fractures (26.7 vs. 11.7%, p = 0.0009), hand and foot fractures (16.0 vs. 5.5%, p = 0.002), other fracture types (5.3 vs. 1.2%, p = 0.02), and osteoporotic fractures (8.0 vs. 1.2%, p < 0.0001) compared to the remaining population. The odds ratio for any fracture was 0.63 (95% CI, 0.49-0.89; p = 0.0003) per SD increase in BMD and was 4.3 (95% CI, 1.9-9.4; p = 0.003) in the lowest BMD quintile compared to the highest quintile. No clinical or biochemical predictors of fracture risk were identified apart from BMD.

Women with obesity who have the lowest BMD values, despite these being almost normal, have an elevated risk of fracture compared to those with higher BMD.