Abstract
INTRODUCTION: The heterogeneity of e-cigarette products and e-liquids pose challenges to surveillance of e-cigarette exposure. The goal of this study was to evaluate the internal consistency of e-cigarette use frequency, quantity, and duration measures in a national population-based survey. METHODS: Data were drawn from the 2012-2013 for the National Epidemiologic Survey on Alcohol and Related Conditions-III (n = 36,309; NESARC-III). Adults who used e-cigarettes/e-liquid during the past year (≤18 years old; n = 1,229) were asked about their age of first use, recency of use, quantity (i.e., cartridges, drops), nicotine concentration, and duration (hours). Several internal consistency parameters were compared for e-cigarette measures in past-year (n = 750) and past 30-day e-cigarette users (n = 472) overall, and by frequency of use (i.e., infrequent [≤3 days/month], non-daily [1-6 days/week], daily). RESULTS: There were no significant differences in quantity, nicotine concentration, or duration by frequency of use in past 30-day e-cigarette users. One-third of past 30-day and almost half of past-year users did not know the nicotine concentration of their cartridge or e-liquid. Correlations between all e-cigarette use measures were low, with the highest correlations seen between e-liquid quantity and cartridge quantity in all past 30-day users (r = 0.28) and those reporting any e-liquid use (r = 0.40). Cronbach's alpha and mean interitem correlations were low across all user groups. CONCLUSIONS: Low to moderate correlation across e-cigarette measures in e-cigarette users implies low internal consistency of these measures in a population survey. Findings suggest measures such as quantity and nicotine concentration might more appropriate in samples of recent experienced e-cigarette users than in general population samples.