Intensity of exposure to tobacco smoke appears to be associated with the rate of metabolic syndrome in a dose-response relationship in adolescents, according to a study in the cross-sectional third National Health and Nutrition Examination Survey.
The study is the first of its kind to associate smoking with metabolic syndrome by using a biologic marker of smoking–serum levels of the nicotine metabolite cotinine–and exposure to environmental tobacco smoke in adolescents, reported Michael Weitzman, M.D., of the University of Rochester (N.Y.) and his colleagues (Circulation 2005;112:862–9).
In the 1988–1994 survey of 2,273 adolescents aged 12–19 years, exposure to environmental tobacco smoke and active smoking were independently tied to nearly fivefold and more than sixfold higher odds of developing metabolic syndrome, respectively, after adjusting for gender, age, race or ethnicity, poverty status, region, and parental history of diabetes or heart attack.
The investigators obtained similar results when they restricted their analysis to individuals with a body mass index at the 85th percentile or higher (those who are overweight and at risk for overweight).
Of 664 adolescents overweight or at risk for overweight, metabolic syndrome occurred at a rate of 5.6% in individuals who were not exposed to tobacco smoke; 19.6% in those exposed to environmental or secondhand smoke; and 23.6% in active smokers. The increase in the rate of metabolic syndrome in adolescents followed a significant trend from those who were not exposed to tobacco smoke, through the lowest to highest level of exposure to environmental tobacco smoke, up to active smokers.
The criteria for metabolic syndrome consisted of a triglyceride level of 110 mg/dL or higher, an HDL cholesterol level of 40 mg/dL or lower, a waist circumference at the 90th percentile or higher, blood pressure in the 90th percentile or higher, and a fasting plasma glucose level of 100 mg/dL or higher.
Their report cannot “conclusively establish an etiologic role for tobacco smoke in the development of metabolic syndrome in youth,” the investigators noted. But a “plausible biologic basis exists for this association” in that “evidence in studies of children suggests that insulin resistance mediates the deleterious effects of excess adiposity on blood pressure and lipids in metabolic syndrome” and “smoking is associated with increased insulin resistance in adults.”
At least two other studies have found increased rates of metabolic syndrome in adult smokers.
