Airflow limitation as a risk factor for low bone mineral density and hip fracture: The Hordaland Health Study (HUSK) – 10 years follow-up of a general population

AIM: To investigate whether airflow limitation is associated with bone mineral density (BMD) and risk of hip fractures. METHODS: A community sample of 5,100 subjects 47–48 and 71–73 years old and living in Bergen was invited. Participants filled in questionnaires and performed a post-bronchodilator spirometry measuring forced expiratory volume in 1 second (FEV(1)) and forced vital capacity (FVC). All attendants were invited to have a BMD measurement of the hip. During 10 years of follow-up, information on death was collected from the Norwegian Cause of Death Registry, and incident hip fractures were registered from regional hospital records of discharge diagnoses and surgical procedure codes. RESULTS: The attendance rate was 69% (n=3,506). The prevalence of chronic obstructive pulmonary disease (COPD) (FEV(1)/FVC<0.7) was 9%. In multiple logistic regression, the lowest quartile of BMD versus the three upper was significantly predicted by FEV(1)/FVC<0.7 and FEV(1)% predicted (odds ratio [OR]: 1.58, 95% confidence interval [CI]: 1.11 to 2.25, and OR per increase of 10%: 0.92, 95% CI: 0.86 to 0.99, respectively). Hip fracture occurred in 126 (4%) participants. In a Cox regression analysis, FEV(1)% predicted was associated with a lowered risk of hip fracture (hazard ratio per increase of 10%: 0.89, 95% CI: 0.79 to 0.997). CONCLUSION: Airflow limitation is positively associated with low BMD and risk of hip fracture in middle-aged and elderly.