The incidence and aetiology of stroke in the Caerphilly and Speedwell Collaborative Studies II: risk factors for ischaemic stroke

Reduction of stroke burden requires preventive interventions targeted at im portant risk factors. This report presents the analysis of risk factors for ischaemic stroke from a representative cohort of middle aged men from Sout h Wales and south-west England. Data on risk factors were collected through validated questionnaires and physical and clinical measurements. Details o f possible cerebrovascular events were retrieved, classified into ischaemic , haemorrhagic and uncertain subtypes, and validated. The ratio of definite ischaemic to definite haemorrhagic strokes was calculated. This showed tha t the vast majority of strokes of unknown subtype were likely to ischaemic. After exclusion of known haemorrhagic strokes and subarrachnoid haemorrhag es the remaining strokes were labelled ischaemic. Hazard ratios for possibl e risk factors were calculated for all ischaemic, and for fatal and non-fat al strokes. There were 293 ischaemic strokes. Statistically significant age -adjusted hazard ratios were. 1.50 (95% confidence interval 1.16-1.95) for brings in a manual social class, 1.82 (1.24-2.67) if smoking > 15 cigarette s/d at enrolment, 1.19 (1.13-1.24) and 1.23 (1.14- 1.34) per 10 mmHg increa se in systolic and diastolic blood pressure, respectively, 0.67 (0.46-0.96) for the top quintile high density lipoprotein-cholesterol:cholesterol rati o compared to the bottom quintile, 2.04 (1.40-2.99) for presence of angina, 3.90 (2.01-7.58) for presence of atrial fibrillation, and 3.35 (1.90-5.80) for presence of diabetes. Risk factors were more strongly associated with fatal than non-fatal strokes. Multivariate analyses revealed that, while th ere was some attenuation of the effect of social class, angina and elevated BP, the risks from atrial fibrillation and diabetes were increased.