The incidence and aetiology of stroke in the Caerphilly and Speedwell Collaborative Studies I: methods and incidence of events

Stroke mortality and morbidity remain high despite downward trends in incid ence and case fatality. Population-based longitudinal studies which include collection of risk factor data are required for a better understanding of stroke aetiology. From a representative cohort of men from South Wales and South-west England, followed up for a median of 17 y, details of possible c erebrovascular events were collected from questionnaires, hospital admissio n data, general practitioner records, death certificates, radiology records and post-mortem reports. Radiology records, and strokes and transient isch aemic attacks were independently validated. There were 433 strokes and 163 transient ischaemic attacks identified during follow-up. Of these, 333 were the first ever in a lifetime strokes of which 139 were definite ischaemic, 20 were haemorrhagic and 168 were probable ischaemic strokes. The crude in cidence rate for stroke was 445 (95% confidence interval 398-493) per 100 0 00 person years. The age-standardised rates for 10 y age-bands were: 45 - 5 4 y 91 (10 - 172); 55-64y 351 (269-432) and 65-74y 855 (669-1040). The 30d case-fatality rate was 21.0% (70/333) for all strokes and 19.2% (60/312) fo r ischaemic strokes. For transient ischaemic attacks the age-standardised i ncidence rates for the same 10y age bands were 92 (4-179), 111 (64-157), an d 273 (167-80), respectively. These rates for stroke transient ischaemic at tack are likely to be accurate given the high ascertainment of events in th is representative population of middle-aged men. Such studies, reporting re liable measures of cerebrovascular events, are important for measuring burd en of disease, and for analysis of risk factor associations to help improve understanding of stroke aetiology and inform preventive efforts.