Infective endocarditis and the association to income as a proxy for socioeconomic position - A Danish nationwide register-based cohort study.

Aims: Despite continued focus on infective endocarditis morbidity and mortality remains high. Socioeconomic position is known to influence the risk of multiple diseases but the impact on the occurrence of infective endocarditis is unknown. We aimed to investigate the association between available income as a proxy for socioeconomic position and infective endocarditis in an unselected nationwide population.

Methods and results: By cross-linking Danish nationwide registers, we identified all Danish residents above 30 years of age, from January 1^st, 2007 through December 31^st, 2017. Information on income, comorbidities and the primary outcome of infective endocarditis was obtained through the registers. Socioeconomic position was defined according to quintiles of disposable income. The association between socioeconomic position and infective endocarditis was examined using multivariate Poisson Regression analyses, incorporating time-updated estimates of disposable income. The study included 3,524,314 individuals (median age = 47 years) with a median follow-up of 11 years. Declining level of income was associated with increasing incidence rates of infective endocarditis, spanning from 7-20 events/100.000 person-years. Individuals with low income had higher incidence rate ratio (IRR) of infective endocarditis compared to individuals with high income (lowest vs. highest income group, IRR = 1.58 [1.43-1.75]). The association between decreasing income and increasing IRR of infective endocarditis was present across all age groups, although the association was strongest in the young population.

Conclusion: In a nationwide population, a significant association between low income and increasing incidence of infective endocarditis was observed. The association was most evident in younger individuals.