Background and PurposeThe association between left atrial size and ischemic stroke is controversial and has been suggested to exist only in men and to be mediated by left ventricular mass. Data are available almost exclusively for white patients. The purpose of this study was to evaluate the association between left atrial size and ischemic stroke in a multiethnic population.MethodsA population-based case-control study was conducted in 352 patients aged >39 years with first ischemic stroke and in 369 age-, gender-, and race-ethnicity-matched community controls. Left atrial diameter was measured by 2-dimensional transthoracic echocardiography and indexed by body surface area. Conditional logistic regression analysis was performed to assess the risk of stroke associated with left atrial index in the overall group and in the age, gender, and race-ethnic strata after adjustment for the presence of other stroke risk factors.ResultsLeft atrial index was associated with ischemic stroke in the overall group (adjusted OR 1.47 per 10 mm/1.7 m2of body surface area; 95% CI 1.03 to 2.11). The association was present in men (adjusted OR 2.81, 95% CI 1.42 to 5.57) but not in women (adjusted OR 1.08, 95% CI 0.70 to 1.66), and in patients aged <60 years (adjusted OR 3.78, 95% CI 1.36 to 10.54) but not >60 years (adjusted OR 1.23, 95% CI 0.84 to 1.81). Subgroup analyses showed the risk to be present in men across all age subgroups. In women, the lack of association between left atrial index and stroke was most strongly influenced by left ventricular hypertrophy. A trend toward an association between left atrial index and stroke was observed in whites (adjusted OR 1.81, 95% CI 0.81 to 4.09) and Hispanics (adjusted OR 1.61, 95% CI 0.98 to 2.65) but was less evident in blacks (adjusted OR 1.25, 95% CI 0.74 to 2.14).ConclusionsLeft atrial enlargement is associated with an increased risk of ischemic stroke after adjustment for other stroke risk factors, including left ventricular hypertrophy. The association is observed in men of all ages, whereas in women it is attenuated by other factors, especially left ventricular hypertrophy. Interracial differences in the stroke risk may exist that need further investigation.