Aims
Autoimmune diseases (AIDs) are associated with a higher risk of heart failure (HF). However, data on the prognosis of HF patients with a history of AID are limited. The aim was to investigate the rates of all-cause mortality and HF hospitalization in a large, nationwide cohort of patient with HF according to a history of 29 AIDs

Methods and results
Using Danish nationwide registries, each HF patient (diagnosed 2000–18) with a history of AID was matched with four HF patients without AID by age, sex, and year of HF diagnosis. Rates of outcomes were compared by Cox regression models. The prevalence of AID in patients with HF was 10.7%. In total, 21 256 HF patients with a history of AID were matched with 85 024 HF patients without AID (median age 77 years; 58.9% female). During a median follow-up of 3.2 years, the incidence rates per 100 person-years for all-cause mortality were 17.1 (95% confidence interval, 16.9–17.4) and 14.4 (14.3–14.6) in patients with and without AID, respectively. The corresponding rates for HF hospitalization were 5.0 (4.9–5.1) and 5.2 (5.1–5.4), respectively. A history of AID was associated with higher rate of all-cause mortality [hazard ratio (HR) 1.14 (1.12–1.17)], but not HF hospitalization [HR 1.00 (0.96–1.04)] compared with no AID.

Conclusions
In a nationwide cohort study, patients with HF and a history of AID had a higher associated rate of mortality than those without a history of AID.