A comparison of nicotine biomarkers and smoking patterns in daily and nondaily smokers.

Nondaily or intermittent smokers (ITS) are increasingly common, but how much nicotine, if any, ITS take in and how quickly they metabolize it has not yet been studied. We compared carbon monoxide (CO), urinary cotinine, and nicotine metabolism [nicotine metabolite ratio (NMR): 3-hydroxycotinine:cotinine] in 224 ITS and 222 daily smokers (DS). Effects of gender and ethnicity were examined. DS had higher cotinine concentrations than ITS (1,396 ± 69 vs. 478 ± 44 ng/mL), attributable to higher cigarettes per day (CPD). In both groups, cotinine rose more slowly as CPD increased. There were no differences in cotinine between White (WH) and African American (AA) DS; among ITS, AA cotinine was over twice that of WH. Among DS, CO was significantly higher among WH than AA smokers, but significantly lower among WH ITS than AA ITS. Although AA ITS smoked more than WH ITS (CPD: 4.13 ± 0.55 vs. 3.31 ± 0.41), this did not account for the observed cotinine nor CO differences. There were no differences in NMR by group or race, nor any gender effects. At comparable CPD, DS' and ITS' intake of nicotine per cigarette was similar, as were their rates of nicotine metabolism. Among ITS, AA smokers smoke more and take in more nicotine per cigarette than WH ITS, consistent with the view of ITS as a heterogeneous group. Differences in nicotine intake per cigarette and metabolism likely cannot account for differences in DS and ITS smoking. Future studies should explore ethnic differences in ITS smoking.