Context: Fractures in obese individuals are of public health importance, but the relationship between obesity and fracture is complex and remains poorly understood. Objective: The study examined the association of body mass index (BMI) with bone structural and strength parameters and incident fracture. Design and Setting: We performed cross-sectional and longitudinal analyses using data from the Manitoba Bone Density Program. Participants: We included 51 313 women and 4689 men aged 50 years or older referred for dualenergy X-ray absorptiometry scans. For 41 919 women and 4085 men, we were able to derive hip structural parameters. Main Outcome Measure: Cross-sectional moment of inertia, cross-sectional area, and femoral strength index were derived from dual-energy X-ray absorptiometry. Health service records were assessed for incident major osteoporotic fractures (MOFs)(meanfollow-up 6.2 y inwomenand4.7 y in men). Results: Among individuals with a BMI of less than 30 kg/m2, increasing BMI was associated with progressive increases in bone mineral density (BMD), cross-sectional moment of inertia, and crosssectional area. The relationship reached a plateau around a BMI of 30 kg/m2, with little additional increment with further increases in BMI (all P for interaction .0001, obese vs nonobese). Increasing BMI was linearly associated with decreases in strength index in both women and men. MOFs were ascertained in 3721womenand 276men(1027 female and 75 male hip fractures). Higher BMI was associated with a lower risk ofMOFinwomenin multivariable models, but this association was largely explained by their higher BMD. Protective association of higher BMI with hip fracture were stronger and only partially explained by BMD (hazard ratio [95% confidence interval] 0.79 [0.73-0.99] for obese I and 0.67 [0.46-0.98] for obese II). Higher BMI was not significantly associated with a risk of MOF or hip fracture in men. Conclusions: Despite structural and biomechanical disadvantages, obesewomenwere at lower risk of fracture.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical