Introduction:
To assess frequency and patterns of e-cigarette use among smokers before, during, and after a hospitalization.

Material and Methods:
Analysis of data from a multi-site randomized controlled trial that enrolled 1357 hospitalized smokers planning to quit, offered two intensities of conventional cessation treatment after discharge, and reached 1100 participants at one month post-discharge. We assessed patterns of e-cigarette use before, during and after hospitalization, reasons for use, and factors associated with use.

Results:
E-cigarettes were used by 21.4% of smokers in the month before hospitalization but were used intermittently (median=4/30 days). E-cigarettes were used by 3.1% of smokers in the hospital and by 18.3% during the month after discharge, primarily as quit aids. At 1 month, 10.6% reported past 7-day e-cigarette use (median=4/7 days), including 4.6% who used e-cigarettes exclusively and 6.1% who also smoked conventional cigarettes. The adjusted odds of e-cigarette use post-discharge were lower among non-Hispanic blacks and higher among smokers who were female, better educated, used e-cigarettes before hospitalization, relapsed to cigarettes in the week after discharge, and were randomly assigned receive less ready access to evidence-based cessation treatments.

Conclusions:
Substantial minorities of smokers who planned to quit used e-cigarettes before and after a hospitalization, primarily to aid quitting, and despite receiving conventional cessation support post-discharge. However, e-cigarette use was intermittent and dual use with cigarettes was common. E-cigarette use was more common among smokers who relapsed soon after discharge and received less intensive cessation help. Funding The Helping HAND 2 trial was funded by NIH/NHLBI grant #R01-HL11821. AH is funded by British Heart Foundation 4-year PhD studentship at University College London. The funding organizations had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; or decision to submit the manuscript for publication.