Population-Attributable Risks for Ischemic Stroke in a Community in South Brazil: A Case-Control Study

Background: Risk factors for ischemic stroke are mostly known, but it is still unclear in most countries, what are their combined population-attributable risk percent (PAR%). In a case-control study the individual odds ratios (ORs) and the individual and combined PAR%, including risk factors not addressed in previous studies were estimated. Methods: Cases and controls were selected from patients attending to an emergency department. Cases were patients aged with 45 years or more with the first episode of ischemic stroke, characterized by a focal neurological deficit or change in the mental status occurring during the previous 24 hours. Controls, matched to cases by age and gender, were selected from patients without neurological complaints. Results: 133 cases and 272 controls were studied. Odds ratios for ischemic stroke were: atrial fibrillation (27.3; CI 95% 7.5-99.9), left ventricular hypertrophy (20.3; CI 95% 8.8-46.4), history of hypertension (11.2; CI 95% 5.4-23.3), physical inactivity (6.6; CI 95% 3.3-13.1), low levels of HDL-cholesterol (5.0; CI 95% 2.8-8.9), heavy smoking (2.8; CI 95% 1.5-5.0), carotid bruit (2.5; CI 95% 1.3-4.6), diabetes (2.4; CI 95% 1.4-4.0) and alcohol abuse (2.1; CI 95% 1.1-4.0), The combination of these risk factors accounted for 98.9% (95% CI; 96.4%-99.7%) of the PAR% for all stroke. Conclusions: Nine risk factors, easily identified, explain almost 100% of the population attributable risk for ischemic stroke.