Sleep-related functional impairment as a moderator of risky drinking and subsequent negative drinking consequences in college students.

OBJECTIVE: Poor sleep quality and insufficient total sleep time have been shown to modify the relationship between college drinking and negative drinking consequences. This study aimed to examine whether prospective associations between risky drinking and negative drinking consequences similarly differ by sleep-related functional impairment, which is novel to the literature.
METHOD: Data were obtained from a 2-month prospective study of 157 college drinkers (mean age = 19 years [SD = 1.11], 30% male, 76% White). Online questionnaires were administered at both Time 1 (T1) and Time 2 (T2) to measure sleep-related functional impairment (assessed by Insomnia Diurnal Impact Scale; Ruiz, Guilera, & Gomez-Benito, 2011) and drinking behaviors and negative drinking consequences (assessed retrospectively over the past 2 months).
RESULTS: Prospective negative binomial regression analyses demonstrated that associations of both maximum drinks and binge drinking frequency at T1 with negative drinking consequences at T2 differed by T1 sleep-related functional impairment after controlling for covariates (sex, negative mood, total sleep time, insomnia symptoms, morning preference, and negative drinking consequences at T1). Students reporting lower sleep-related functional impairment experienced high levels of negative drinking consequences only at high levels of risky drinking, whereas students reporting higher sleep-related functional impairment experienced consistently high levels of negative drinking consequences regardless of their risky drinking levels.
CONCLUSION: Findings indicate that sleep-related functional impairment may exacerbate negative drinking consequences of risky drinking. Thus, sleep-related functional impairment helps to explain individual differences in the association between risky drinking and negative drinking consequences in college students.