Changes in Cigarettes per Day and Biomarkers of Exposure Among US Adult Smokers in the Population Assessment of Tobacco and Health Study Waves 1 and 2 (2013-2015).

Introduction: Some studies have found some reduction in tobacco exposure and tobacco-related disease risk with decreased numbers of cigarettes smoked per day (CPD), but biomarker of exposure estimates by change in CPD are generally unavailable for the US population.

Methods: We analyzed biomarker of exposure data by smoking status from over 1100 adult exclusive daily cigarette smokers in Wave 1 of the Population Assessment of Tobacco and Health (PATH) Study who were either exclusive daily smokers or had quit tobacco use entirely at Wave 2. Wave 1 smoking categories consisted of "very light" (1-4 CPD), "light" (5-9 CPD), "moderate" (10-19 CPD), and "heavy" (20+ CPD), and Wave 2 categories were "quitters" (stopped smoking entirely), exclusive cigarette "reducers" (CPD decreased ≥ 50%), "maintainers" (CPD within 50%-150% of Wave 1 value), and "increasers" (CPD increased ≥ 50%).

Results: Complete quitters had significantly lower levels of TNE-2, NNAL, NNN, 2-Fluorene, HPMA, CYMA, and MHB3 at Wave 2 for all Wave 1 CPD categories, and decreases were often large. Moderate "reducers" had lower levels of NNAL and 1-Hydroxypyrene at Wave 2, and heavy "reducers" had lower levels of NNAL, 2-Fluorene, and MHB3. Light "increasers" had higher levels of TNE-2, NNAL, 2-Fluorene, CYMA, and cadmium at Wave 2, and heavy "increasers" had higher levels of NNAL and HPMA.

Conclusions: Smoking "reducers" and "increasers" had changes in some biomarker of tobacco exposure levels, but reductions were much greater and more consistent for complete quitters.

Implications: PATH longitudinal cohort study data show that some exclusive daily cigarette smokers increase or decrease CPD over time. These differences may result in moderate changes in the levels of some biomarkers such as NNAL. Even so, however, reductions in biomarker levels are much greater with complete smoking cessation.