OP0247 PERSISTENT PREMATURE MORTALITY GAP IN IDIOPATHIC INFLAMMATORY MYOPATHY: A GENERAL POPULATION-BASED COHORT STUDY
Authors: K. D’silva, L. Lu, A. Ogdie, A. Aviña, H. Choi
Journal: Annals of the Rheumatic Diseases (2020)

Background: Idiopathic inflammatory myopathy (IIM) is associated with significant premature mortality; however, whether the mortality gap has improved over recent years is unknown. Objectives: To determine trends in premature mortality in patients with IIM in a large cohort, representative of the United Kingdom (UK) general population. Methods: Using The Health Improvement Network (THIN), an electronic medical record database representative of the UK general population, we identified patients with incident IIM between 18 and 89 years of age (defined by at least one Read diagnosis code for dermatomyositis, polymyositis, or interstitial myositis with at least one year of continuous enrollment in THIN prior to the cohort entry date) and up to 10 controls without IIM matched on age, sex, birth year, and database entry year. The cohort was divided in two based on the year of IIM diagnosis: the early cohort (1999-2006) and the late cohort (2007-2014). We calculated adjusted hazard ratios for death using a multivariable Cox-proportional hazards model and adjusted rate differences using an additive hazard model. Results: The early cohort consisted of 355 patients with IIM and 3182 matched controls, while the late cohort consisted of 396 IIM patients and 3551 matched controls. In both cohorts, IIM patients had excess mortality compared to matched controls [57.4 vs. 15.2 deaths/1000 person-years (PY) in the early cohort and 43.2 vs. 14.1 deaths/1000 PY in the late cohort] (Table). The corresponding multivariate mortality hazard ratios were 2.73 (95% CI, 1.85 to 4.03) vs. 2.61 (95% CI, 1.75 to 3.89) in the early and late cohorts, respectively (p-value for interaction = 0.63) (Figure). The absolute multivariate mortality differences were 36.6 (95% CI, 20.4 to 52.8) and 25.8 (95% CI, 13.7 to 37.9) deaths/1000 PY, in the early and late cohorts, respectively (p-value for interaction = 0.24). Conclusion: In this general population-based cohort study, patients with IIM had over 2.5 times the risk of death compared to matched controls, even after adjusting for comorbidities and medications. Unlike trends seen in rheumatoid arthritis and granulomatosis with polyangiitis, there appears to be no improvement in mortality in IIM in recent years. This highlights the need for improved strategies for the management of patients with IIM and its comorbidities. Table. Association between idiopathic inflammatory myopathy (IIM) and all-cause mortality according to time period. 1999-2006 2007-2014 IIM cohort (n=355) Non-IIM cohort (n=3182) IIM cohort (n=396) Non-IIM cohort (n=3551) p-value for interaction Follow-up time, years (mean ± SD) 2.6 ± 2.1 2.9 ± 2.1 3.2 ± 2.4 3.5 ± 2.4 Number of deaths 53 140 55 177 Death rate/1000 PY (95% CI) 57.4 (43.0, 75.1) 15.2 (12.7, 17.9) 43.2 (32.5, 56.2) 14.1 (12.1, 16.3) Age-, sex-, and entry year-matched hazard ratio (95% CI) 4.02 (2.89, 5.59) 1.00 (ref) 3.43 (2.49, 4.73) 1.00 (ref) 0.50 Multivariable-adjusted hazard ratio (95% CI)* 2.73 (1.85, 4.03) 1.00 (ref) 2.61 (1.75, 3.89) 1.00 (ref) 0.63 Age-, sex-, and entry year-matched rate difference/1000 PY (95% CI) 42.2 (26.6, 57.9) 0.0 (ref) 29.1 (17.5, 40.7) 0.0 (ref) 0.24 Multivariable-adjusted rate difference/1000 PY (95% CI) 36.6 (20.4, 52.8) 0.0 (ref) 25.8 (13.7, 37.9) 0.0 (ref) 0.24 * Multivariable models were adjusted for age, sex, entry year, number of GP visits, BMI, smoking status (i.e., non-smokers, ex-smokers, current smokers), alcohol consumption (i.e., non-drinkers, ex-drinkers, current drinkers), comorbidities, and medication use. PY, person-year; BMI, body mass index; GP, general practitioner Figure. Cumulative mortality of patients with idiopathic inflammatory myopathy and matched controls without IIM in early versus late cohorts (1999-2006 versus 2007-2014). Disclosure of Interests: Kristin D’Silva: None declared, Leo Lu: None declared, Alexis Ogdie Grant/research support from: Pfizer to Penn, Novartis to Penn, Amgen to Forward/NDB, Consultant of: Abbvie, Amgen, Bristol-Myers Squibb, Celgene, Corrona, Janssen, Eli Lilly, Novartis, Pfizer, Antonio Aviña: None declared, Hyon Choi Grant/research support from: Ironwood, Horizon, Consultant of: Takeda, Selecta, Horizon, Kowa, Vaxart, Ironwood