Meta-analysis of the association between cigarette smoking and peripheral arterial disease

CONTEXT: Smoking is an important risk factor for peripheral arterial disease (PAD). OBJECTIVE: To undertake a meta-analysis of the association between cigarette smoking and PAD. DATA SOURCES: Medline, Embase, PubMed and Web of Science databases. STUDY SELECTION: Relevant studies published up to 30 April 2012 were identified. DATA EXTRACTION: Performed by two researchers. Overall and stratified random effects meta-analyses, cumulative meta-analyses and metaregression analyses were conducted. Heterogeneity was tested using the I(2) test, and publication and small study bias using funnel plots and Egger's test. RESULTS: Fifty-five eligible studies were identified: 43 cross-sectional, 10 cohort and 2 case-control. Of the 68 results for current smokers, 59 (86.8%) were statistically significant and the pooled OR was 2.71 (95% CI 2.28 to 3.21). There was a high level of heterogeneity (I(2) 94.9%, p<0.001) and Egger's test was significant (p=0.023). The association with smoking was significant among both general (OR 3.08, 95% CI 2.56 to 3.69) and disease populations (OR 1.54, 95% CI 1.31 to 1.83). Of the 40 results for ex-smokers, 29 (72.5%) were statistically significant and the pooled OR was 1.67 (95% CI 1.54 to 1.81). There was moderate heterogeneity (I(2) 54.7%, p<0.001) and Egger's test was significant (p<0.001). CONCLUSIONS: There is now substantial evidence of an association between active smoking and PAD. The magnitude of the association is greater than that reported for coronary heart disease. The risk is lower among ex-smokers but, nonetheless, significantly increased compared with never smokers. The results highlight the need for interventions both to encourage quitting among existing smokers and discourage commencement among never smokers.