Is there an independent association between metabolic syndrome and smoking in Iranian adults? Results of a large multicenter national survey

Background: Theoretically, smoking status should be associated with metabolic syndrome. This relationship has not been studied in Iranian population so far. This study aimed to explore the association among cigarette smoking, metabolic syndrome (MetS) and its domains in a nationally representative sample of Iranians aged 25-64. Methods: Information of participants regarding demographic data and smoking habits gathered through WHO STEPS questionnaires in the frame of fourth national surveillance of the risk factors of non-communicable diseases in 2011 across the country. The fasting plasma glucose, triglyceride level, high-density lipoprotein cholesterol (HDL-C) level, blood pressure, and anthropometric indices in each patient were measured. Data of 4000 subjects were analyzed with complex sample survey method. The prevalence of metabolic syndrome was assessed according to two definitions: International Diabetes Federation (IDF) and Iranian definition. Results: Herein, 38.4% of smoker participants and 36.6% of non-smokers met the IDF criteria for MetS (P=0.67). Similarly, 31.1% of smokers and 34.1% of non-smokers had MetS according to Iranian-IDF (P=0.427). Only in univariate analysis, using IDF criteria female smokers had lower prevalence of MetS than non-smokers (13.9% vs. 36.5%, P=0.01). Multivariate analysis determined the following odds ratios for the association of smoking with MetS defined by IDF and Iranian-IDF criteria, respectively: OR= 0.89 (0.53- 1.47), P=0.638 and OR= 0.97 (0.59-1.58), P=0.901. Conclusion: There was no significant association between smoking and MetS overall and among men. However, smoking was associated with lower prevalence of MetS among women.