Trends in myocarditis incidence, complications and mortality in Sweden from 2000 to 2014

Investigate trends in myocarditis incidence and prognosis in Sweden during 2000-2014. Little data exist concerning population-trends in incidence of hospitalizations for myocarditis and subsequent prognosis. Linking Swedish National Patient and Cause of Death Registers, we identified individuals >= 16 years with first-time diagnosis of myocarditis during 2000-2014. Reference population, matched for age and birth year (n = 16,622) was selected from Swedish Total Population Register. Among the 8 679 cases (75% men, 64% < 50 years), incidence rate/100,000 inhabitants rose from 6.3 to 8.6 per 100,000, mostly in men and those < 50 years. Incident heart failure/dilated cardiomyopathy occurred in 6.2% within 1 year after index hospitalization and in 10.2% during 2000-2014, predominantly in those >= 50 years (12.1% within 1 year, 20.8% during 2000-2014). In all 8.1% died within 1 year, 0.9% (< 50 years) and 20.8% (>= 50 years). Hazard ratios (adjusted for age, sex) for 1-year mortality comparing cases and controls were 4.00 (95% confidence interval 1.37-11.70), 4.48 (2.57-7.82), 4.57 (3.31-6.31) and 3.93 (3.39-4.57) for individuals aged < 30, 30 to < 50, 50 to < 70, and >= 70 years, respectively. The incidence of myocarditis during 2000-2014 increased, predominantly in men < 50 years. One-year mortality was low, but fourfold higher compared with reference population.

Automated summary

This study investigated the incidence and prognosis of myocarditis in Sweden from 2000 to 2014. The results showed an increasing trend in myocarditis incidence during this period, predominantly in men and individuals under 50 years of age. The incidence of heart failure and dilated cardiomyopathy was relatively low, but the one-year mortality rate was significantly higher compared to the reference population.