Relationship between smoking habits and the features of the metabolic syndrome in a non-diabetic population

IntroductionCigarette smoking is a risk factor for type 2 diabetes mellitus. The effect of smoking on the pathogenic factors for the development of diabetes is little explored. We evaluate the relation of smoking with the features of the insulin resistance syndrome, insulin resistance, and insulin secretion.Methods2412 non-diabetic men, aged 35–65 years, were studied. Smoking habit was investigated by questionnaire. Anthropometry, blood pressure, forced expiratory volume (FEV1), fasting glucose, triglycerides, total and HDL cholesterol, plasma free fatty acids (FFA), insulin and fibrinogen were measured. HOMA-IR and HOMA β cell were calculated. The metabolic syndrome was defined according to ATP III criteria.ResultsThe metabolic syndrome was more prevalent in smokers than non-smokers (OR: 1.34; 95% CI 1.01–1.77). This was mainly due to a higher prevalence of dyslipidemia – high triglycerides (46.1% vs 29.9%, p < 0.001), or low HDL cholesterol (42.2% vs 30.4%, p < 0.001), in smokers. In smokers, other features of insulin resistance – i.e. obesity, hypertension, and hyperglycemia were significantly less frequent and FFA were lower (p < 0.001). Plasma insulin and HOMA β cell were similar in the two groups (8.3 vs 8.0 μU/ml and 80.7% vs 82.9%, respectively), but HOMA-IR was significantly lower in smokers (p < 0.001) due to the lower glucose values observed in these people.ConclusionsAmong the features of the metabolic syndrome, only dyslipidemia is associated with chronic smoking. Smoking in not associated with enhanced insulin resistance, or with impaired insulin secretion. Alternative hypotheses should be explored for the increased risk of diabetes in smokers.