Scrub typhus increases the risk of developing acute coronary syndrome: a nationwide cohort study

Background Studies investigating the epidemiological relationship between scrub typhus and the subsequent development of acute coronary syndrome (ACS) are lacking. Therefore, we conducted a nationwide longitudinal cohort study in Taiwan to explore whether patients with scrub typhus are at an increased risk of developing ACS. Methods This study investigated the incidence and risk factors for ACS in 5215 patients newly diagnosed with scrub typhus from the Taiwan National Health Insurance Research Database between 2000 and 2011. The comparison cohort contained 20 860 persons from the general population without scrub typhus. The follow-up period ran from the time of the initial diagnosis for scrub typhus to the date of an ACS event, censoring, or 31 December 2011. We used Cox proportional hazard regression models to analyse the risk of ACS by including the variables of sex, age and comorbidities. Results The incidence of ACS was higher in patients with scrub typhus than in the comparison cohort (3.10 vs 1.92 per 1000 person-years). The HR of developing ACS increased by 37% in patients with scrub typhus after adjusting for age, sex and comorbidities. Men, increased age, hypertension, diabetes, hyperlipidaemia, chronic obstructive pulmonary disease and coronary artery disease were identified as independent risk factors of developing ACS after controlling for covariates. The prominent effect of scrub typhus on subsequent ACS development appeared within 1 year after infection. Conclusions This nationwide study determined that patients with scrub typhus exhibited a 37% increase in the risk of subsequently developing ACS compared with that of the general population.