Underweight increases the incidence of infective endocarditis in the Korean population: a nation-wide cohort study.

Background: In general, obesity is associated with infectious diseases, however, the relationship between underweight and infectious disease is controversial. Moreover, the association between body mass index (BMI) and the incidence of infective endocarditis (IE) has not been studied to date. Therefore, we investigated the relationship between BMI and incidence of IE in the Korean population.

Methods: We analyzed 4,080,331 participants (mean age 47.12 ± 14.13 years) from the National Health Insurance health checkup database. Hazard ratios (HRs) and 95 % confidence intervals (CIs) for IE incidence according to five BMI levels were calculated using multivariable Cox proportional hazards models with or without IE risk.

Results: During the 9-year follow-up, the incidence rate of IE was 3.244 persons per 100,000 person-years in the underweight group, 2.023 in normal weight, 2.105 in overweight, 2.133 in obesity stage I, and 3.294 in obesity stage II. After adjusting for all covariates, overall HR for the incidence of IE increased among participants with IE risk in all BMI levels compared to subjects without IE risk when the normal weight group without IE risk was designated as the reference group. An increase in the HR for the incidence of IE was observed only in underweight subjects in both the total and no IE risk groups [HR: 2.01 (95 % CI, 1.46-2.77); HR: 2.01 (95 % CI, 1.45-2.78)].

Conclusion: Underweight is associated with increased risk of developing IE, especially in subjects without IE risk. Considering increasing incidence of IE, clinicians should pay more attention to underweight patients with no IE risks.