Objectives: We examined the impact of cigarette filter collection on reports of cigarettes per day (CPD) versus self-reported CPD and to assess the utility of a pre-intervention baseline period in smoking studies.
Methods: Using baseline data from 522 non-treatment seeking smokers, we assessed differences in self-reported CPD via phone screen (CPD PS) and during baseline (CPD BL). We analyzed self-reported cigarette measures to predict carbon monoxide (CO), a measure of smoke exposure.
Results: On average, CPD PS was 2.8 CPD more than CPD BL, and reporting multiples of 10 were more often found in CPD PS compared with CPD BL (54.7% vs17.2%, respectively). CPD BL was more strongly associated with CO than self-report CPD. Number of cigarettes smoked today, time since last cigarette, and nicotine dependence were significantly associated with CO.
Conclusions: CPD BL using filter collection is a more accurate measure of cigarette consumption than self-report, which may have implications for assessment of nicotine dependence. When feasible, studies should include a pre-intervention baseline period for comparison data with study outcomes. In addition to CPD BL, studies should assess time since last cigarette and the number of cigarettes smoked today when using CO as a biological measure of smoke exposure.
Keywords: measuring cigarettes per day; methodology in smoking studies; nicotine dependence.