Incidence and risk factors of intracranial atherosclerotic stroke: The northern manhattan stroke study

Background: To assess the prevalence of risk factors as determinants of intracranial atherosclerosis (IATH)-related stroke in a multi-ethnic community-based cohort. Methods: The Northern Manhattan Stroke Study included a population-based incidence study and a nested case-control study. Incident cases of first ischemic stroke were 1:2 when matched to community controls by age, sex, and race/ethnicity. Vascular risk factors were assessed among controls and compared against the following stroke subtypes: IATH, extracranial atherosclerosis (EATH), and non-atherosclerotic (NATH: cardioembolic, lacunar, and cryptogenic). Conditional logistic-regression was used to determine the association between risk factors and stroke subtypes. Results: The crude incidence of IATH was 8/100,000 per year and the relative incidence of IATH was higher than that of EATH in blacks (5.9 vs. 3.2/100,000 per year) and in Hispanics (5.0 vs. 1.7/100,000 per year). The IATH group had a higher prevalence of diabetes mellitus (DM; 67% IATH, 60% EATH, 48% NATH, and 23% controls; p < 0.05 IATH vs. control) and of metabolic syndrome (62% IATH, 40% EATH, 40% NATH, and 35% controls; p < 0.05 IATH vs. control). In multivariate analysis, DM conferred a higher risk for IATH versus NATH stroke (OR, 10.8; 95% CI, 2.0-57 vs. OR, 2.7; 95% CI, 1.9-3.9; p < 0.05) and much lower for EATH (OR, 6.2; 95% CI, 1.2-32). The metabolic syndrome conferred a higher risk for IATH stroke subtype (OR, 4.6; 95% CI, 1.1-18.7) when compared to EATH (OR, 2.3; CI, 0.6-9.1) and NATH (OR, 2.4; CI, 1.7-3.3). Conclusions: DM is a more important determinant for IATH-related stroke than EATH or NATH.