Socioeconomic Inequalities in All-Cause and Cause-Specific Mortality Among Patients With Osteoarthritis in the Skane Region of Sweden

Objective To assess the association between education and all-cause and cause-specific mortality among patients with osteoarthritis (OA) in comparison to an OA-free reference cohort. Methods Using data from the Skane Healthcare Register, we identified all residents age >= 45 years in the region of Skane in southern Sweden with doctor-diagnosed OA of peripheral joints between 1998 and 2013 (n = 123,993). We created an age- and sex-matched reference cohort without OA diagnosis (n = 121,318). Subjects were followed until death, relocation outside Skane, or the end of 2014. The relative index of inequality (RII) and the slope index of inequality (SII) were estimated by the Cox model and Aalen's additive hazard model, respectively. Results We found an inverse association between education and mortality. The magnitude of relative inequalities in all-cause mortality were comparable in the OA, with an RII of 1.53 (95% confidence interval [95% CI] 1.46, 1.61), and reference cohorts (RII 1.54 [95% CI 1.47, 1.62]). The absolute inequalities were smaller in the OA cohort (all-cause deaths per 100,000 person-years, SII 937 [95% CI 811, 1,063]) compared with the reference cohort (SII 1,265 [95% CI 1,109, 1,421]). Cardiovascular mortality contributed more to the absolute inequalities in the OA cohort than in the reference cohort (60.1% versus 48.1%) while the opposite was observed for cancer mortality (8.5% versus 22.3%). Conclusion We found higher all-cause and cause-specific mortality in OA patients with lower education. The observed inequalities in the OA cohort reflect the inequalities in the population at large. The greater burden of cardiovascular diseases in OA patients suggests that proper management of cardiovascular risk factors in OA patients is important.