BMI, Waist Circumference, and Risk of Incident Vertebral Fracture in Women

Objective The study aimed to investigate the association between BMI, waist circumference, and vertebral fracture (VF) risk in women. Methods This prospective study was conducted in 54,934 Nurses' Health Study participants. BMI was assessed biennially, and waist circumference was assessed in the year 2000. Self-reports of VF were confirmed by record review. BMI reflects lean body mass, and waist circumference reflects abdominal adiposity when included in the same regression model. Results This study included 536 VF cases (2002 to 2014). Compared with women with BMI of 21.0 to 24.9 kg/m(2), the multivariable-adjusted relative risk (RR) of VF for women with BMI >= 32.0 was 0.84 (95% CI: 0.61-1.14; P-trend = 0.08). After further adjustment for waist circumference, the multivariable-adjusted RR of VF for women with BMI >= 32.0 was 0.70 (95% CI: 0.49-0.98; P-trend = 0.003). Compared with women with waist circumference < 71.0 cm, the multivariable-adjusted RR of VF for women with waist circumference >= 108.0 cm was 1.76 (95% CI: 1.06-2.92; P-trend = 0.01), and after further adjustment for BMI, the multivariable-adjusted RR of VF was 2.49 (95% CI: 1.44-4.33; P-trend < 0.001). Conclusions Greater lean body mass was independently associated with lower VF risk. Larger waist circumference was independently associated with higher VF risk. These findings suggest that fat distribution is an important predictor of VF and that avoiding central adiposity, as well as maintaining muscle mass, may potentially confer reduced risk of VF in older women.