Incidence, Event Rates, and Early Outcome of Stroke in Dublin, Ireland

BACKGROUND AND PURPOSE: The World Health Organization has emphasized the importance of international population-based data for unbiased surveillance of stroke incidence and outcome. To date, few such studies have been conducted using recommended gold-standard ascertainment methods. We conducted a large, population-based stroke study in Dublin, Ireland. METHODS: Using gold-standard ascertainment methods, individuals with stroke and transient ischemic attack occurring over a 12-month period (December 1, 2005-November 30, 2006) in North Dublin were identified. Disability was assessed using the modified Rankin score and stroke severity (<72 hours) by the National Institutes of Health Stroke Scale. Stroke-related deaths were confirmed by review of medical files, death certificates, pathology, and coroner's records. Crude and standardized (to European and World Health Organization standard populations) rates of incidence, risk factors, severity, and early outcome (mortality, case-fatality, disability) were calculated, assuming a Poisson distribution for the number of events. RESULTS: Seven hundred one patients with new stroke or transient ischemic attack were ascertained (485 first-ever stroke patients, 83 recurrent stroke patients, 133 first-ever transient ischemic attack patients). Crude frequency rates (all rates per 1000 person-years) were: 1.65 (95% CI, 1.5-1.79; first-ever stroke), 0.28 (95% CI, 0.22-0.35; recurrent stroke), and 0.45 (95% CI, 0.37-0.53; first-ever transient ischemic attack). Age-adjusted stroke rates were higher than those in 9 other recent population-based samples from high-income countries. High rates of subtype-specific risk factors were observed (atrial fibrillation, 31.3% and smoking, 29.1% in ischemic stroke; warfarin use, 21.2% in primary intracerebral hemorrhage; smoking, 53.9% in subarachnoid hemorrhage; P<0.01 for all compared with other subtypes). Compared with recent studies, 28-day case-fatality rates for primary intracerebral hemorrhage (41%; 95% CI, 29.2%-54.1%) and subarachnoid hemorrhage (46%; 95% CI, 28.8%-64.5%) were greater in Dublin. CONCLUSIONS: Using gold-standard methods for case ascertainment, we found high incidence rates of stroke in Dublin compared with those in similar high-income countries; this is likely explained in part by high rates of subtype-specific risk factors.