Effects of duration of electronic cigarette use.

INTRODUCTION This study examined the effect of duration electronic cigarette (e-cigarette) use on e-cigarette dependence, frequency of use, and strength of nicotine solution as well as number of cigarettes smoked per day. METHODS Individuals were recruited at e-cigarette retail locations in a large Midwestern metropolitan city of the United States in July 2013. A total of 159 participants completed a brief 29-item self-report measure that assessed behaviors and perceptions of use. The mean age of the participants was 35.8 years; 84.4% were White, and 53.7% were male. RESULTS Increased duration of e-cigarette use was associated with fewer cigarettes smoked per day and differing patterns of dependence to e-cigarettes contingent upon smoking history. Additionally, increased duration of e-cigarette use was associated with increased frequency of use; however, this finding became nonsignificant when current tobacco cigarette use was accounted for, suggesting that individuals may increase e-cigarette use frequency as they decrease cigarette use. Overall, e-cigarette users tended to decrease the strength of nicotine in their e-cigarette products regardless of duration of use. CONCLUSIONS Although preliminary in nature, this study identifies several factors that are important to consider when examining the effects of prolonged e-cigarette use. The implications of the current results should be informative to future studies that examine these variables in longitudinal designs.