Gender differences in tobacco smoking: higher relative exposure to smoke than nicotine in women.

INTRODUCTION Men and women are thought to regulate their smoking differently and to differ in their susceptibility to nicotine addiction. METHODS AND MATERIALS Various measures of smoke exposure were compared between 400 current regular tobacco-dependent (DSM-IV) male and female light (1-15 cigarettes per day) and heavy (>15 cigarettes per day) smokers. Between 2 and 8 PM, blood was collected for nicotine and cotinine analysis, and breath carbon monoxide (CO) was measured. Individuals with genetic variants of the CYP2A6 gene were removed from analysis (n = 25). RESULTS No significant difference was found in the number of cigarettes per day or CO levels between the sexes. However, females had significantly lower nicotine levels than males (16.9 +/- 0.6 vs. 21.1 +/- 0.07, p < 0.01). This is only partly explained by the fact that females smoked lower nicotine-containing cigarettes. Female heavy smokers demonstrated higher -log nicotine/CO values (a representation of cost of smoking) compared with male heavy smokers (0.1 +/- 0.02 vs. 0.02 +/- 0.01 mg/L ppm, p < 0.05). CONCLUSIONS Thus, gender differences appear to exist in smoking behaviors, nicotine sensitivity, and nicotine requirements. These differences are expected to contribute to gender differences in health risks and cancers associated with smoking.