Prospective epidemiologic evidence of a “protective” effect of smoking on metabolic syndrome and diabetes among Turkish women—Without associated overall health benefit

Sex-specific effects of cigarette smoking on the development of metabolic syndrome (MS) and diabetes (DM), concomitant with its clinical impact on CHD, were prospectively evaluated in a cohort of 3385 participants (mean age 48 years), representative of Turks. Heavy smoking denoted smoking 11 or more cigarettes daily. During a mean 5.9-year follow-up, 485 incident cases of MS and 216 of DM were diagnosed. Among women, baseline characteristics as a whole were similar. Smoking status was inversely associated with waist circumference (p = 0.004) and predicted in women hyperinsulinemia (p = 0.045) after adjustment for age and body mass index. In the prediction of MS, heavy smoking was significantly “protective” (RR 0.50 [95% CI 0.26; 0.94]) in women and in both genders combined, after adjustment for age, baseline family income bracket and physical activity grade. As predictor of new DM, heavy smoking was significantly “protective” (RR 0.54 [95% CI 0.35; 0.83]) in all adults and in women (RR 0.13 [95% CI 0.02; 0.97]), after similar adjustment. Additional adjustment for insulin and CRP levels hardly modified in women the RRs, though attenuated to borderline significance risk for MS and DM due to smaller sample size. Risks of incident CHD and overall mortality were significantly elevated in smoking men, but not in women, when adjusted for age, serum total cholesterol, elevated BP, DM and physical activity grade. Conclusions: Heavy cigarette smoking is “protective” of future MS and DM in Turkish women, mainly via protection from obesity. A separate modest effect on central obesity appeared independent of plasma insulin concentrations. Evidence of a translated beneficial effect on subsequent CHD or all-cause mortality did not emerge.