Active smoking and risk of metabolic syndrome: a meta-analysis of prospective studies.
BACKGROUND
Epidemiological evidence suggests that smoking has been associated with emergence of metabolic syndrome. However, data on this issue are inconsistent and controversial. We therefore conducted a meta-analysis to examine the association between smoking and metabolic syndrome.


RESULTS
We searched the Medline, Embase and the Cochrane Library database up to March 2012 to identify prospective cohort studies related to smoking and metabolic syndrome. Reference lists of retrieved articles were also reviewed. Summary effect estimates were derived using a random-effects model and stratified by gender, smoking dose, follow-up duration and geographical area. Primary analysis of 13 studies involving 56,691 participants and 8,688 cases detected a significant positive association between active smoking and risk of metabolic syndrome (pooled relative risk [RR] 1.26, 95% CI: 1.10-1.44). Estimates of effects were substantially consistent in the stratified analyses. In the dose-response analysis, risk of metabolic syndrome was stronger for active male smokers (pooled RR 1.34, 95% CI: 1.20-1.50) than it was for former male smokers (pooled RR 1.19, 95% CI: 1.00-1.42), and greater for heavy smokers (pooled RR 1.42, 95% CI: 1.27-1.59) compared with light smokers (pooled RR 1.10, 95% CI: 0.90-1.35). No evidence of statistical publication bias was found (Egger' s test P=0.227, Begg' s test P=0.113).


CONCLUSIONS
Active smoking is associated with development of metabolic syndrome. Smoking cessation appears to reduce the risk of metabolic syndrome.
Key Laboratory for Endocrine and Metabolic Diseases of Ministry of Health, Rui-Jin Hospital, Shanghai Jiao Tong University School of Medicine, E-Institute of Shanghai Universities, Shanghai, China.
Kan
K
Sun
Jianmin
J
Liu
Guang
G
Ning
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D008297:Male; D024821:Metabolic Syndrome / Q000209:etiology*; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D016540:Smoking Cessation; D055815:Young Adult