Incidence of osteoporosis and fragility fractures in asthma: a UK population-based matched cohort study

Introduction: Osteoporosis and fragility fractures are associated with corticosteroids which are the mainstay treatment for asthma; however, these bone comorbidities within asthma need to be better described. Methods: A matched cohort study was conducted using the UK Clinical Practice Research Database (CPRD). Adults with an incident asthma code were identified and matched, with up to four randomly selected people without asthma, by age, sex and practice. Osteoporosis and fragility fracture incidence rates were calculated, and Cox regression was performed comparing hazard rates to the general population. We report the impact of age, sex, glucocorticoids and the risk of specific fractures. Results: Patients with asthma had a higher risk of osteoporosis (adjusted hazard ratio (aHR) 1.18, 95% CI 1.13-1.23) and were 12% (aHR 1.12, 95% CI 1.07-1.16) more likely to sustain fragility fractures than the general population. Age modified the effect of asthma on osteoporosis and fragility fractures, such that the effect was stronger in younger people (P-interaction <0.0001). The vertebra (aHR 1.40, 95% CI 1.33-1.48) and forearm/wrist (aHR 1.27, 95% CI 1.22-1.32) were the sites linked with a larger incidence. A dose-response relationship between oral corticosteroids (OCS) and osteoporosis was observed, whereas the risk of fragility fractures increased in those with six or more OCS courses per year. Regular use of inhaled corticosteroids (ICS) increased the risk of both bone conditions. Conclusions: Patients with asthma are more likely to develop osteoporosis or sustain fragility fractures than the general population, with a particular concern in younger people and those more frequently using OCS and ICS.