Risk of hip fracture in Addison's disease: a population-based cohort study

Objectives. The results of studies of bone mineral density in Addison's disease (AD) are inconsistent. There are no published data on hip fracture risk in patients with AD. In this study, we compare hip fracture risk in adults with and without AD. Design. A population-based cohort study. Methods. Through the Swedish National Patient Register and the Total Population Register, we identified 3219 patients without prior hip fracture who were diagnosed with AD at the age of >= 30 years during the period 1964-2006 and 31 557 age-and sex-matched controls. Time to hip fracture was measured. Results. We observed 221 hip fractures (6.9%) in patients with AD and 846 (2.7%) in the controls. Patients with AD had a higher risk of hip fracture [hazard ratio (HR) = 1.8; 95% confidence interval (CI), 1.6-2.1; P < 0.001]. This risk increase was independent of sex and age at or calendar period of diagnosis. Risk estimates did not change with adjustment for type 1 diabetes, autoimmune thyroid disease, rheumatoid arthritis or coeliac disease. Women diagnosed with AD <= 50 years old had the highest risk of hip fracture (HR = 2.7; 95 % CI, 1.6-4.5). We found a positive association between hip fracture and undiagnosed AD [odds ratio (OR) = 2.4; 95 % CI, 2.1-3.0] with the highest risk estimates in the last year before AD diagnosis (OR = 2.8; 95 % CI, 1.8-4.2). Conclusion. Both clinically undiagnosed and diagnosed AD was associated with hip fractures, with the highest relative risk seen in women diagnosed with AD <= 50 years of age.