Intermittent Claudication : Prevalence and metabolic risk factors
Abstract: The prevalence of intermittent claudication (IC) in middle-aged men (45-69 years old) and metabolic risk factors for this disease was studied in a Swedish community. All 15 253 middle-aged male residents in Linköping community, were screened for symptoms of IC using a postal questionnaire, which included detailed questions about smoking habits and presence of hypertension and diabetes mellitus.The overall response rate was 86.6% (n=l3 209). The prevalence of walking-related pain was 9.3% (n=l232), and 4.2%(n=552) had symptoms consistent with peripheral atherosclerotic disease (PAD). All men with leg symptoms according to the classical Rose criteria for IC (1.2%, n=156), and a sample of subjects (0.6%, n=84) with symptoms indicating PAD, but not fully complying with the Rose c.riteria, were invited for further examination.Subjects with IC were compared with randomly selected sex- and age-matched controls from the same population. One control group was matched for smoking habits (n=157), and one control group consisted of never-smokers (n=143). Both claudicants and healthy controls underwent objective examination of the peripheral circulation with segmental blood pressure measurements and a short treadmill exercise test.IC could objectively be verified in 1.7% (n=219) of all middle-aged men. The prevalence of IC was highly age-dependent and objectively verified IC increased from 0.2% in males 45-49 years old to 3.4% in those 65-69 years old. The prevalence of Rose IC was 0.5% for 45-49 year-old males and 2.0% for 65-69 year-old males. Thus the Rose criteria underestimated the prevalence ofiC in the older age group and overestimated it in the youngest age group. The estimated true average prevalence ofiC was at least 2.8%.More than half (57%) of all claudicants had ischaemic heart disease, and 21% had experienced a TIA or stroke.The metabolic studies investigated the role of dyslipidaemia and various metabolic abnormalities as risk factors for IC. Claudicants had multiple minor and moderate lipid and lipoprotein abnormalities, the strongest association being with elevated plasma levels of low-density lipoproteins (LDL) cholesterol and low levels of high-density lipoproteins (HDL) cholesterol, after multivariate adjustment for other major risk factors, i.e. hypertension, diabetes mellitus and smoking, and other factors that influence lipid levels. Ve1y-low-density lipoproteins (VLDL) triglycerides had a high univariate association, but did not contribute to risk for IC after multivariate adjustment for the above factors.Plasma lipoprotein (a) [Lp(a)] showed a strong association with risk for IC, which in part could be explained by a significant overrepresentation of small apo(a) isoforms, genetically associated with higher Lp(a) concentrations.Plasma a- and ~-carotene, Iycopene and retinol, but not a- or y-tocophcrol (vitamin E), showed a multivariate significant association with risk for IC in men. However, when dietary data had been accounted for, only the significance of plasma retinol remained. Lower plasma levels of lipid-soluble antioxidants after adjustment for lipid concentrations may be secondary to the atherosclerotic disease. Moderately elevated levels of plasma homocyst(e)ine, a su\fbydryl-containing amino acid with a known atherogenic potential, were significantly associated with risk of IC after adjustment for other risk factors in multivariate analyses.In conclusion, the risk for IC amongst middle-aged males was significantly associated with presence of both major traditional risk factors such as smoking (96%), hypertension (49%), diabetes mellitus (18%) and additional metabol~c risk factors such as dyslipidaemia, hypcrhomocyst(e)inaemia and elevated Lp(a) levels. Plasma levels of tocophero!s (vitamin E) were not associated with risk for IC. Carotenoids do not seem to contribute, whereas the role of plasma retinol remains unclear.
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