Incidence of and risk of mortality after hip fractures in Rheumatoid Arthritis relative to the general population.

Abstract

Objectives: Osteoporosis, a known complication of rheumatoid arthritis (RA), increases the risk of hip fracture, which is associated with high morbidity and mortality. Fracture risk estimates in RA patients treated with contemporary treatment strategies are lacking. The objectives were 1) to estimate age- and sex-specific incidence rates and compare the risk of hip fractures in RA relative to age and sex-matched general population controls, and 2) to compare the risk of all-cause mortality in RA and general population controls after hip fracture.

Methods: A longitudinal study of a population-based incident cohort of RA patients diagnosed between 1997 and 2009, followed until 2014, with age- and sex-matched controls from the general population of British Columbia, using administrative health data. Hip fracture outcomes (ICD9-CM codes 820.0 or 820.2; ICD10-CA code S72.0 to S72.2) and mortality at pre-defined intervals after fracture (in-hospital, 90 days, 1-year, 5-year) were identified. Hip fracture incidence rates for RA and controls, and incidence rate ratios (IRR) were calculated. Cox proportional hazards models compared hip fracture and mortality risk in RA vs. controls; logistic regression compared in-hospital mortality risk.

Results: Overall, 1314 hip fractures over 360,521 person-years were identified in 37,616 RA individuals and 2083 over 732,249 person-years in 75,213 controls, yielding a 28% greater fracture risk in RA (IRR 1.28 [95%CI, 1.20;1.37]). Mean age at time of fracture was slightly younger for RA than controls (79.6 + 10.8 vs. 81.6 + 9.3 yrs). Post-fracture mortality risk at 1- and 5-years did not differ between RA and general population controls. Results were similar in a sensitivity analysis including only RA individuals who received disease-modifying antirheumatic drugs (DMARDs).

Conclusion: People with RA had a greater risk of hip fractures, but no greater risk of mortality post fracture, than the general population. The relative risk of hip fractures observed was not as high as previously reported, likely reflecting better treatment of inflammation and management of osteoporosis and its risk factors.