Endocarditis usually occurrs more frequently in men, gender derived ratios range from 1.6 to 2.5. The age specific incidence of endocarditis increased progressively after 30 years of age and exceed 15 to 30 cases per 100,000 person-years in the sixth through eighth decades of life. From 55 to 75 per cent of patients with native valve endocarditis (NVE) have predisposing conditions like rheumatic heart disease, congenital heart disease, mitral valve prolapse, degenerative heart disease, asymmetrical septal hypertrophy, or intravenous drug abuse. From 7 to 25 per cent of cases involve prosthetic valves. Predisposing conditions cannot be identified in 25 to 45 per cent of patients. The nature of predisposing conditions and in part the microbiology of IE correlate with the age of patients.
Rheumatic fever with subsequent rheumatic heart disease in children and young adults is still the most common predisposing cause for IE in developing countries. In recent decades, only the increasing role of intravenous (IV) drug abuse as predisposition for IE and the high IE risk in children and young adults surviving after correction of complex congenital heart disease favour the occurrence of infection in younger patients and the incidence has increased in the elderly because of the increased longeivity and the associated prevalence of degenerative valvular heart disease.