Epidemiology of ischemic stroke subtypes: results from the follow-up of a population-based registry

BACKGROUND:Stroke is the leading cause of disability and the second most common cause of death worldwide.Stroke registries are important to formulate guidelines and to improve health services and medical assistance. AIM:To obtain recent epidemiological data on first-ever ischemic stroke (FEIS)(Chapter III) and of ischemic stroke etiologic subtypes(Chapter IV);to evaluate the contribution of atrial fibrillation (AF) to the incidence and prognosis of FEIS, and to evaluate possible epidemiological changes over two decades comparing these recent data on AF with those from the 1994-1998 study(Chapter V);to evaluate the contribution of AF diagnosed after stroke onset (newly diagnosed atrial fibrillation; NDAF) to the incidence, and prognosis of FEIS(Chapter VI). METHODS:All the residents in the district of L’Aquila diagnosed with a FEIS in 2011-2013 were included in a prospective population-based registry and were followed up to 5 years. Case-fatality and vascular events were assessed. RESULTS:Among the 1,280 patients with first-ever stroke included in the registry, 919(71.8%)had a FEIS(52.8% women; mean age±SD, 76.5±12.0 years);women were 6.8 years older at FEIS onset as compared with men. The crude incidence rate of FEIS was 102.68 per 100,000 person-years, 93.89 when standardized to 2011 Italian population, and 79.09 when standardized to the 2011 European population. The case-fatality rate (CFR) of FEIS patients was 18.0% at 30 days, 28.2% at 1 year, and 43.4% at 5 years. The 5-year cumulative probability of survival in patients with FEIS was 56.6%.The distribution of etiologic subtypes according to TOAST criteria was as follows: large-artery atherosclerosis (12.8%), cardioembolism (CE; 34.9%), small artery occlusion (11.9%), other causes (4.7%), undetermined causes (35.7%). CE strokes had the highest incidence rate, were more severe and more disabling, had the highest 30-day, 1-year, and 5-year CFRs, and the lowest 5-year survival with respect to those with other etiologic subtypes. The Cox analysis showed that CE was an independent predictor of morality at 1 year, that was mostly driven by the associated higher stroke severity. Among 919 FEIS, 9 patients without ECG evaluation were excluded and AF was documented in 32.3%. Stroke severity, post-stroke disability, and 30-day, 1-year and 5-year CFRs were significantly higher in patients with AF than in those without. The arrhythmia was NDAF in 22.4% and PDAF in 77.6%. Mean age and vascular risk factors profile was similar in patients with NDAF and PDAF. Patients with NDAF had more severe strokes, greater residual disability discharge, and higher CFRs. From 1994-1998 to 2011-2013 there was a decrease from of the relative proportion of FEIS, a 75% decrease of FEIS incidence, and a decrease in 30-day and 1-year mortality. While, there was an overall 31.3% increase of AF prevalence, and a 44% reduction of the incidence rate ratio and a decrease in 30-day and 1-year mortality in patients with and without AF. CONCLUSIONS:We found in our population a fairly low incidence of FEIS, low rates of vascular follow-up events, and similar CFRs compared to concurrent registries. CE is the current most common stroke etiological subtype and AF is the most prevalent risk factor in this group. These results are likely due to effective primary preventive measures, and improved ischemic stroke management during the acute phase, nevetheless, a better diagnosis and management of atherothrombotic vascular risk factors contributed to the reduction of the FEIS incidence over two decades, and to the increase of CE- and AF-related strokes. Given the high burden of stroke due to CE and in particular to AF, primary preventive measures targeting detection and treatment of cardiac risk factors, the implementation of preventive thromboembolic strategies and the education of patients to maintain treatment adherence might contribute to reduce not only stroke occurrence but also its severity and prognosis.