Effects of duration of electronic cigarette use.
BACKGROUND
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.
Department of Psychology, Oklahoma State University, Stillwater, OK; Oklahoma Tobacco Research Center, Oklahoma City, OK; william.lechner@okstate.edu.
William V
WV
Lechner
Department of Psychology, Oklahoma State University, Stillwater, OK; Oklahoma Tobacco Research Center, Oklahoma City, OK;
Alayna P
AP
Tackett
Department of Psychology, Oklahoma State University, Stillwater, OK; Oklahoma Tobacco Research Center, Oklahoma City, OK;
DeMond M
DM
Grant
Oklahoma Tobacco Research Center, Oklahoma City, OK; University of Oklahoma Health Sciences Center , Oklahoma City, OK.
Noor N
NN
Tahirkheli
Oklahoma Tobacco Research Center, Oklahoma City, OK; University of Oklahoma Health Sciences Center , Oklahoma City, OK.
Leslie M
LM
Driskill
Oklahoma Tobacco Research Center, Oklahoma City, OK; University of Oklahoma Health Sciences Center , Oklahoma City, OK.
Theodore L
TL
Wagener
D000328:Adult; D066300:Electronic Nicotine Delivery Systems / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D009538:Nicotine / Q000008:administration & dosage; D016540:Smoking Cessation / Q000379:methods*; D000074606:Smoking Prevention; D013997:Time Factors
D009538:Nicotine