Objective. Although the link between low bone mineral density (BMD) and fracture is well established, the association between aged-related bone loss and fracture remains controversial. In this study, we aimed at testing the hypothesis that excessive bone loss is associated with increased fracture risk in elderly women.
Methods. This study involved 5581 women who were a part of the Study of Osteoporotic Fractures and had undergone a minimum of three BMD assessments. Femoral neck BMD was measured using DXA (Hologic QDR 1000) between 1992 and 2008. The rate of BMD change was determined by a linear mixed-effects regression model for each woman. The incidence of fractures (after 3 BMD measurements) was ascertained by reviewing hospital discharge records or physician reports. The Cox's proportional hazards model was utilized to assess the association between bone loss and fracture risk, while also accounting for pre-defined covariates such as baseline BMD, age, smoking, drinking, physical activity, prior and family history of fractures.
Results. During the median follow-up of 13 years (IQR: 9-17), there were 1470 incident fractures (including 679 hip fractures), yielding fracture incidences of 25 per 1000 person-years (95% CI: 23-26). The rate of bone loss was significantly associated with an increased risk of any fracture (hazard ratio: 1.18; 95% CI: 1.07-1.30) and hip fracture (1.30; 95% CI: 1.13-1.50). Importantly, those with an excess annual bone loss (e.g., at least 2% per year) were associated with a 2-fold (95% CI: 1.01-4.0) increase in hip fracture risk.
Conclusion. These data support the hypothesis that bone loss at the femoral neck is a risk factor for fracture, independent of age and baseline BMD. This suggests that repeated measurements of BMD can be useful in identifying individuals who are at high risk of fracture.