Background: Lung cancer rates are lower in Asians and Latinos than in whites. Ethnic differences in nicotine metabolism might explain, in part, ethnic differences in cigarette consumption and/or nicotine intake per cigarette and resultant tobacco-related cancer risk. We compared the rate of nicotine metabolism and the intake of nicotine per cigarette smoked among smokers of different ethnicities.
Methods: Healthy volunteer smokers, including 37 Chinese-Americans, 40 Latinos, and 54 whites, received simultaneous infusions of deuterium-labeled nicotine and cotinine, a metabolite of nicotine. From blood and urine measurements, the disposition kinetics and daily intake of nicotine from smoking were determined. All statistical tests were two-sided.
Results: Total and nonrenal clearance of nicotine and cotinine and metabolic clearance of nicotine via the cotinine pathway were similar in Latinos and whites and statistically significantly lower in Chinese-Americans. Intake of nicotine per cigarette by Chinese-Americans (0.73 mg; 95% confidence interval [CI] = 0.53 to 0.94 mg) was statistically significantly lower than that by Latinos (1.05 mg; 95% CI = 0.85 to 1.25 mg) or whites (1.10 mg; 95% CI = 0.91 to 1.30 mg; P =.039). Among all of the participants, there was a statistically significant positive correlation between nicotine clearance and daily intake of nicotine from cigarette smoking and between nicotine clearance and nicotine intake per cigarette (r =.41 and r =.39, respectively) (P<.001 for both).
Conclusions: The lower nicotine (and, therefore, tobacco smoke) intake per cigarette and the fewer cigarettes smoked per day, which may result, in part, from slower clearance of nicotine, may explain lower lung cancer rates in Chinese-Americans. Lower lung cancer rates among Latinos compared with whites, given their similar nicotine intake per cigarette, are probably due to smoking fewer cigarettes. The results with Chinese-Americans may have implications for dosing with nicotine medications to aid smoking cessation in Chinese- American smokers and perhaps in other Asian smokers.