Long-term fracture risk following adult-onset asthma: a population-based study

Abstract

There are few data on skeletal outcomes in the growing population of patients with adult-onset asthma. We conducted a population-based retrospective (historical) cohort study among 226 residents of Rochester, Minnesota, USA, who were 35 years of age or older when first diagnosed with asthma. Fractures were ascertained by review of comprehensive community medical records, and observed fractures were compared with expected numbers based on incidence rates in the local population (standardized incidence ratios, SIR). During 4,022 person-years of follow-up, 100 patients experienced 211 fractures, for an actuarially estimated cumulative incidence of 63% after 30 years compared with 59% expected ( p=0.004). Statistically significant increases were seen for moderate trauma fractures of the vertebrae (SIR, 2.9; 95% CI, 2.1 to 3.8) and ribs (SIR, 2.0; 95% CI, 1.2 to 3.2), as well as the proximal femur (SIR, 1.8; 95% CI, 1.02 to 2.8). As assessed by proportional hazards models, the only independent predictors of any subsequent moderate trauma fracture were age (hazard ratio [HR] per 10-year increase, 1.7; 95% CI, 1.5 to 2.1) and cumulative corticosteroid dose greater than the median of 1,775 mg (HR, 1.8; 95% CI, 1.1 to 3.0). In another multivariate analysis, the predictors of a moderate trauma vertebral fracture were older age (HR, 1.6; 95% CI, 1.3 to 2.1), concomitant chronic obstructive pulmonary disease (HR, 2.4; 95% CI, 1.2 to 4.9), cigarette smoking (HR, 2.3; 95% CI, 1.2 to 4.8), and cumulative corticosteroid dose greater than the median (HR, 2.6; 95% CI, 1.4 to 5.0). Other asthma therapies did not contribute significantly to these models. Thus, a 70% increase in overall fracture risk among unselected community patients with adult onset asthma was mainly confined to the subset who also had chronic obstructive pulmonary disease and was influenced by substantial corticosteroid use.