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Introduction
Lifestyle behaviours such as smoking, 1 2 3 physical activity, 4 5 and diet 6 7 influence the risk of cardiovascular disease, including stroke. These lifestyle behaviours are also related to risk factors for cardiovascular diseases such as hypertension, 8 hypercholesterolaemia, 9 and obesity. 10 The impact of combined health behaviours on risk of stroke independently of these intermediate risk factors in an apparently healthy general population, however, is less well documented.
High intake of fruit and vegetables, as indicated by plasma vitamin C concentrations, 11 and more physical activity at work and during leisure time 12 are associated with a lower incidence of stroke. Previously we looked at the combined impact of four health behaviours-smoking, physical activity, alcohol intake, and fruit and vegetable intake-on total and cause specific mortality in men and women living in the general community. 13 As these health behaviours could beneficially affect the incidence of stroke we examined the potential magnitude of their combined impact on incidence of stroke in men and women aged 40-79.
Methods
The participants were 20â[euro][per thousand]040 men and women aged 40-79 at baseline, drawn from the Norfolk component of the European Prospective Investigation of Cancer (EPIC-Norfolk). This prospective population study first surveyed participants in 1993-7, 99.5% of whom were white. The detailed recruitment strategy and sample distribution of the whole cohort have been previously described. 14 Briefly, our participants were recruited from age-sex registers of general practices. As nearly all people in the United Kingdom are registered with general practitioners through the National Health Service, the age-sex registers form a population based sampling frame. From the inception of the EPIC-Norfolk cohort, data collection was broadened to enable the examination of a wider range of determinants of chronic diseases, including stroke. The Norfolk cohort was comparable with national population samples with respect to characteristics including anthropometry, blood pressure, and lipids but with a lower prevalence of current smokers. 14
At the 1993-7 baseline survey, participants completed a detailed health and lifestyle questionnaire. They were asked about medical history with the question "Has a doctor ever told you that you have any of the following?" followed by a list of conditions that included heart attack, stroke, diabetes, and cancer. Smoking history was derived from yes/no responses...