A new study suggests that students who initiate and/or continue drinking and engage in binge drinking in college have more delayed sleep timing and more variable sleep schedules.

Results show that heavier drinkers had later bedtimes and rise times, and more day-to-day variability in sleep length, bedtime and rise time.

"These data indicate that students who initiate drinking and engage in binge drinking in college have more delayed sleep timing and a greater mismatch between circadian phase and sleep timing," said lead author Eliza Van Reen, assistant professor, department of psychiatry and human behavior, Alpert Medical School of Brown University in Providence, R.I.

The research abstract was published recently in an online supplement of the journal Sleep and was presented Wednesday, June 10, in Seattle, Washington, at SLEEP 2015, the 29th annual meeting of the Associated Professional Sleep Societies LLC.

The study group comprised 878 students. The mean age was 18 and 57 percent were female. Students completed a Phase 1 survey in spring before fall college enrollment (high school) and submitted online daily sleep and drink diaries from day 1 of college. Any indication of alcohol use from Phase 1 measures was assigned positive for pre-collegiate drinking. From daily diary, male binge assignment was equal to five or more alcoholic drinks on one day; female binge drinking was equal to four or more. Three groups were derived from those negative for high school drinking: none equal to no college drinking; some equal to drinking one binge day or less and heavy equal to more than one binge day. A fourth group (drinker) included students that were positive for drinking in high school who reported more than one binge event in college.