The relationship between cigarette smoking and cardiovascular risk factors in peripheral arterial disease compared with ischaemic heart disease

Cigarette smoking is probably the most important risk factor for the development of peripheral arterial disease, but if may be less important in the aetiology of ischaemic heart disease. The objectives of this study were to determine whether an), other cardiovascular risk factors showed a significant inter action with cigarette smoking which would explain the greater association between smoking and peripheral atherosclerosis. One thousand five hundred and ninety-two subjects aged 55-74 years were selected randomly from the age-sex registers of 10 general practices in Edinburgh, Scotland. The presence of peripheral arterial disease was determined by the World Health Organisation questionnaire on intermittent claudication, the ankle brachial pressure index and a reactive hyperaemia test. Heart disease was identified by the patients' recall of a doctor diagnosis of angina or myocardial infarction. There were 131 subjects with peripheral arterial disease but no ischaemic heart disease, and 169 with heart disease without peripheral disease. Significantly more smokers occurred in the peripheral than the heart disease group (P<0.01), and in current smokers the age and sex adjusted odds ratio were highly significant for peripheral arterial disease (odds ratio 5.09, 95% confidence inter val 2.97-8.72, P<0.001), but not for heart disease (odds ratio 1.72, 95% confidence interval 0.98-2.33, P>0.05). Subjects with lower limb disease also had higher systolic pressures (P<0.001), serum high density lipoprotein cholesterol (P<0.01) and plasma fibrinogen (P<0.05). On logistic regression, adjusting for a range of individual risk factors had no significant impact on the effect of smoking. Plasma fibrinogen produced the biggest reduction in odds ratio (4.23, 95% confidence interval 2.44-7.35, in current smokers with peripheral arterial disease). Therefore the stronger association between smoking and peripheral arterial disease than ischaemic heart disease does not appear to be influenced by the other risk factors examined here, and must be explained by some other mechanism.