UBC Faculty Research and Publications

The Impact of Systemic Lupus Erythematosus on the Risk of Newly Diagnosed Hip Fracture : A General Population-Based Study Li, Lingyi; Xie, Hui; Lu, Na; Esdaile, John M.; Aviña-Zubieta, Juan Antonio

Abstract

Objective: Hip fractures have serious consequences, including a one-year mortality rate of 30%. Population-based studies on hip fractures in individuals with systemic lupus erythematosus (SLE) are scarce. This study assesses the independent risk of hip fractures in patients with newly diagnosed SLE compared to the general population, accounting for baseline and time-varying confounders. Methods: A cohort of all patients with incident SLE who received healthcare between January 1, 1997 and March 31, 2015 was assembled. The outcome was first hip fracture after study entry. Non-SLE individuals were randomly selected from the general population and matched (5:1) to those with SLE on age-, sex-, and index year. Cumulative incidence was produced after accounting for competing risks of death. Marginal structural Cox models were used to estimate the impact of SLE on hip fractures, adjusting for baseline and time-dependent covariates (i.e., glucocorticoid use and number of outpatient, inpatient and rheumatologist visits). Results: Among 5,047 incident SLE and 25,235 non-SLE individuals (86% female, mean age 40), we found 73 and 272 hip fractures during 78,915 and 395,427 person-years, respectively. The crude incidence rate ratio was 1.34 (95% CI; 1.02-1.75). After adjusting for baseline covariates, the hazard ratio (HR) was 1.86 (95% CI; 1.37-2.52). The HR after further adjustment for time-dependent covariates remained significant (HR=1.62 [95% CI; 1.06-2.48]). Conclusion: Patients with newly diagnosed SLE have a 62% increased risk of hip fractures compared to non-SLE individuals. This result has important implications for prevention of osteoporosis in SLE patients that may lead to hip fractures.

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