Background: Recent studies have demonstrated a declining trend in RA mortality relative to the general population (1). This improvement in mortality could be due to improvement in incident risk of cardiovascular events that are the leading cause of excess deaths in RA (2).
Objectives: Our objective was to assess secular trends in ten-year incident risk of acute myocardial infarction (AMI) in incident cohorts of RA versus general population controls, using administrative health data.
Methods: We conducted a retrospective study of a population-based cohort of incident RA cases who first met previously published RA criteria between 01/01/1997 and 31/12/2004 in British Columbia, followed until 12/2014, with general population controls matched 2:1 on gender, age, and index year. Individuals were excluded if they had a diagnosis of MI prior to index date. Incident AMI was defined as first AMI during follow-up using ICD codes (ICD-9 code 410/ICD-10 code I21) in Hospital Discharge data or death certificate in Vital Statistics data. RA and general population cohorts were stratified according to year of RA incidence, defined according to first RA visit, using a 7-year wash-out period. Incident rates (IRs) of AMI for RA and general population cohorts, as well as incident rate ratios (IRRs), with 95% confidence intervals (CI) were calculated per calendar years of incidence. Multivariable Cox Proportional Hazard models with left truncation were used to estimate risk of AMI in RA relative to general population while controlling for potential confounders, with contribution of person time of follow-up starting from index date (second RA visit) to avoid immortal time bias and censoring at ten years from incident year, or last health care utilization. To examine whether secular trends differed in RA relative to general population, an interaction term was tested between the RA indicator and year of RA incidence. To account for non-linear effect of cohort year, we compared cox regression models with linear, quadratic, and flexible spline forms of the cohort-year effects and the model with the best AIC was used to interpret the data.
Results: 23,237 RA individuals (66.4% female; mean [SD] age 58[16.88] years) and 46,474 controls experienced 1,133 and 1,646 incident AMI, respectively. Cox Proportion model with the lowest AIC best fit the data. Risk of AMI was significantly higher in RA vs. general population [aHR (95% CI): 1.21(1.10, 1.32); p<0.001]. A significant decline was observed in risk of AMI over calendar year of incidence in both RA [0.94(0.92, 0.97); p<.0001] and controls [0.93(0.91, 0.95); p<.0001]. The decline in AMI risk did not differ significantly in RA vs. general population [interaction p=0.555].
Conclusion: Our finding suggests that the risk of AMI has significantly decreased over time in RA and general population cohorts. However, the declining trend was not significantly different in RA compared to the general population.
References:  Lacaille, D., et al., Improvement in 5-year mortality in incident rheumatoid arthritis compared with the general population—closing the mortality gap. Annals of the Rheumatic Diseases, 2016.
 Myasoedova, E. and S.E. Gabriel, Overview of rheumatoid arthritis and mortality in relation to cardiovascular disease, in Handbook of Cardiovascular Disease Management in Rheumatoid Arthritis, A.G. Semb, Editor. 2017, Springer International Publishing: Cham. p. 1-17.
Disclosure of Interests: Kiana Yazdani: None declared, Hui Xie: None declared, Antonio Aviña: None declared, Yufei Zheng: None declared, Michal Abrahamowicz: None declared, Diane Lacaille Grant/research support from: Bristol-Myers Squibb and Eli Lilly Canada
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