Tissue-Based Stroke Definition Impacts Stroke Incidence but not Ethnic Differences

We explored how the new, tissue-based stroke definition impacted incidence estimates, including an ethnic comparison, in a population-based study.

Stroke patients, May, 2014-May, 2016 in Nueces County, Texas were ascertained and validated using source documentation. Overall, ethnic-specific and age-specific Poisson regression models were used to compare first-ever ischemic stroke and intracerebral hemorrhage (ICH) incidence between old and new stroke definitions, adjusting for age, ethnicity, sex, and National Institutes of Health Stroke Scale score.

Among 1308 subjects, 1245 (95%) were defined as stroke by the old definition and 63 additional cases (5%) according to the new. There were 12 cases of parenchymal hematoma (PH1 or PH2) that were reclassified from ischemic stroke to ICH. Overall, incidence of ischemic stroke was slightly higher under the new compared to the old definition (RR 1.07; 95% CI 0.99-1.16); similarly higher in both Mexican Americans (RR 1.06; 95% CI 1.00-1.12) and Non Hispanic whites (RR 1.09, 95% CI 0.97-1.22), p(ethnic difference)=0.36. Overall, incidence of ICH was higher under the new definition compared to old definition (RR 1.16; 95% CI 1.05-1.29), similarly higher among both Mexican Americans (RR 1.14; 95% CI 1.06-1.23) and Non Hispanic whites (RR 1.20, 95% CI 1.03-1.39), p(ethnic difference)=0.25.

Modest increases in ischemic stroke and ICH incidence occurred using the new compared with old stroke definition. There were no differences between Mexican Americans and non Hispanic whites. These estimates provide stroke burden estimates for public health planning.