Correlates of NNAL levels among nondaily and daily smokers in the college student population

Carla J Berg,¹ Gillian L Schauer,¹ Jasjit S Ahluwalia,² Neal L Benowitz<sup>3

1</sup>Department of Behavioral Sciences and Health Education, Emory University School of Public Health, Atlanta, GA, ²Department of Medicine and Center for Health Equity, University of Minnesota, Minneapolis, MN, ³Departments of Medicine and Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA

Introduction: Recent simultaneous increases in nondaily smoking and decreases in daily smoking make the identification of nondaily smokers through biomarker measures as well as the relationship of biomarker levels to smoking behaviors important topics. However, little is known about biochemical identification and carcinogen exposure of nondaily smokers. One tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), has a long half-life, making it a useful marker for long-term and intermittent tobacco exposure. Thus, we examined correlates of urine NNAL levels among nondaily and daily smokers.
Methods: In 2011, we obtained urine samples from 64 current cigarette smokers (37 nondaily; 27 daily) in the Southeastern US and assessed participants’ sociodemographics, smoking-related information, and other tobacco use. Our sample included 14 participants concurrently using other combustible tobacco products and eight concurrently using smokeless tobacco.
Results: Of six participants smoking for only one day in the past 30, four had detectable NNAL levels; thus, two nondaily smokers were excluded from the remainder of the analyses. In multivariate analysis, average cigarettes per day on smoking days (B = 23.00, 95% Confidence Interval [CI] 13.81, 32.20, P < 0.001) and number of days of smokeless tobacco use (B = 17.11, CI 13.53, 20.70, P < 0.001) were associated with NNAL levels among nondaily smokers (R² = 0.234). Multivariate analysis indicated that average cigarettes per day (B = 15.83, CI 2.89, 28.76, P = 0.02) was the only significant correlate of NNAL levels among daily smokers. We used receiver operating characteristic (ROC) analyses to identify a potential urinary NNAL (normalized for creatinine) cutoff point of 81.6 pg/mL/g creatinine (88.9% sensitivity, 80.0% specificity) to discriminate nondaily from daily smokers. Excluding polytobacco-product users from these analyses provided similar results.
Conclusion: Different correlates of NNAL levels exist among nondaily and daily cigarette smokers. Urine NNAL demonstrates the potential to be used to discriminate nondaily from daily smokers among young adults.

Keywords: biomarkers, smoking, carcinogen, tobacco