Incidence of first stroke: a population study in Iceland.

BACKGROUND AND PURPOSE: Iceland is an island in the North Atlantic with ≈319 000 inhabitants. The study determines the incidence of first stroke in the adult population of Iceland during 12 months, which has not been previously reported in the entire Icelandic population. METHODS: The study population consisted of all residents of Iceland, aged ≥ 18 years, during the 12-month study period. Cases were identified by multiple overlapping approaches. Medical records were reviewed to verify diagnosis, to determine stroke subtype and to determine selected risk factors. RESULTS: A total of 343 individuals, aged ≥ 18 years, had a first stroke during the study period. Incidence was 144 per 100 000 person years; 81% ischemic infarction; 9% intracerebral hemorrhage; 7% subarachnoid hemorrhage; and 3% unknown. Fifty percent of the individuals were men. Mean age for ischemic infarction and intracerebral hemorrhage was 71 years for men and 73 years for women. Atrial fibrillation was previously known in 18% with first ischemic stroke or intracerebral hemorrhage and another 6% were diagnosed on routine admission ECG. Long-term ECG study (24 hours) found that 12% (18/154) of the remaining individuals had paroxysmal atrial fibrillation. CONCLUSIONS: Incidence of first stroke in Iceland is similar to other Western countries. The high number of paroxysmal atrial fibrillation found during the 24-hour ECG suggests that atrial fibrillation may be underdiagnosed in patients with stroke.