Electronic Cigarette Use and Chronic Respiratory Symptoms among U.S. Adults.

INTRODUCTION The use of electronic cigarettes (e-cigarettes) for vaporized nicotine delivery is increasing in the United States, especially among young adults. While marketed as a safer alternative to tobacco, little is known about their potential health impacts. We sought to determine the association of current e-cigarette use with chronic respiratory symptoms, and whether the association was modified by tobacco smoking status or age.