Epidemiology and prognosis of peripheral arterial occlusive disease (PAOD)

Peripheral arterial disease has received less attention from epidemiologists than coronary and cerebrovascular disease. Prevalence and incidence data typically show that peripheral arterial disease increases with age, is more common in men than women, and that symptomatic disease is only the tip of the iceberg. Studies concerning the prevalence of peripheral arterial disease rely mainly on the Rose questionnaire, which is used to screen for intermittent claudication, and on the ankle/brachial index, used to detect asymptomatic disease. Although there is a certain parallel between the 2 sets of data, the figures for asymptomatic disease consistently surpass those for clinical disease, and there is a wide variation between frequencies obtained in individual studies. In general, the prevalence of peripheral arterial disease is estimated to be under 2% for men aged less than 50 years, increasing to over 5% in those aged more than 70 years. Women reach these rates almost 10 years after men, although this gender difference decreases with increasing age. Figures for incidence follow a similar trend. The incidence of chronic critical ischaemia is estimated to be between 0.05% and 0.1% of the population. Asymptomatic disease detected with noninvasive tests is 3 to 4 times more frequent than intermittent claudication: its prevalence increases from under 5% for individuals aged less than 50 years to over 20% for individuals aged more than 70 years. The classical risk factors for atherosclerosis also apply to peripheral arterial disease, although their order of importance may be different from that for coronary and carotid disease. Several studies have shown that peripheral arterial disease correlates most strongly with cigarette smoking. Smoking is also the single greatest predictor of the progression of peripheral arterial disease. Other risk factors include hypertension, raised lipid levels (cholesterol and triglycerides for severe disease), diabetes, increased plasma viscosity, fibrinogen and homocysteine levels. Divergent views have been expressed in individual epidemiological studies with regard to the respective contribution of these risk factors to the development and progression of peripheral arterial disease. The natural history of peripheral arterial disease is characterised by a relatively benign local evolution. It can be estimated that, in general, 3 of 4 men presenting with intermittent claudication will never have a serious problem necessitating vascular intervention, and that no more than 5% are ever likely to require a major amputation. However, the underlying atherosclerotic pathology progresses with time: nondiseased arteries become obliterated and disease with an initially unilateral pattern frequently progresses to become bilateral. In addition, the few patients who do progress to critical ischaemia are at a significantly higher risk of amputation. The general prognosis for patients with peripheral arterial disease is particularly negative. There is a high prevalence of coronary heart disease and cerebrovascular disease in such patients, although the exact percentages depend on the patient population selected and on the method used for their evaluation. Coronary heart disease is detected in 40 to 60% of patients through a medical history combined with electrocardiography, while systematic coronary angiography detects coronary heart disease in 90% of those undergoing surgery. Although few patients with peripheral arterial disease have a history of stroke, in studies of surgical patients almost 30% appear to have significant extracranial disease. Patients with peripheral arterial disease have a poor life expectancy: the mortality rate is 3 to 5% per year in those with intermittent claudication and 20% per year in those with critical ischaemia. Coronary heart disease accounts for half of the total mortality, while vascular disease in general accounts for almost two-thirds.