For many, an alcoholic drink before sleeping acts as a sedative, but will later disrupt sleep, according to a new study.
The sedative effect is marked by the delta frequency electroencephalogram (EEG) activity of Slow Wave Sleep (SWS), but is later associated with sleep disruption, according to researchers at the University of Melbourne in Australia.
The researchers note that significant reductions in EEG delta frequency activity and power also occur with normal development between the ages of 12 and 16 — a time when alcohol is commonly consumed for the first time, with dramatic increases in drinking occurring among college-age individuals.
“People likely tend to focus on the commonly reported sedative properties of alcohol, which is reflected in shorter times to fall asleep, particularly in adults, rather than the sleep disruption that occurs later in the night,” said Christian L. Nicholas, Ph.D., of the University of Melbourne, corresponding author for the study.
“The reduction in delta frequency EEG activity we see across the ages is thought to represent normal brain maturational processes as the adolescent brain continues to develop to full maturity,” he continued.
“Although the exact function of non-Rapid Eye Movement (NREM) sleep, and in particular SWS, is a topic of debate, it is thought to reflect sleep need and quality, thus any disruption to this may affect the underlying restorative properties of sleep and be detrimental to daytime functioning.”
For the study, Nicholas and his colleagues recruited 24 volunteers (12 female, 12 male), who were healthy 18- to 21-year-old social drinkers who had consumed less than seven standard drinks a week during the previous 30 days.
Each underwent two conditions: pre-sleep alcohol as well as a placebo, followed by standard polysomnography with comprehensive EEG recordings.
The study findings showed that alcohol increased SWS delta power during NREM. However, there was a simultaneous increase in frontal alpha power.
“For individuals researching sleep in the field of alcohol studies, our findings indicate that care needs to be taken when interpreting increases in ‘visually scored’ SWS associated with alcohol consumption,” Nicholas said.
“Increases in SWS, which traditionally would be interpreted as a good thing, can be associated with more subtle changes indicating disrupted sleep, such as the increases we observed in alpha activity, which are revealed when more detailed micro-structural components of the sleep electroencephalogram are assessed.”
Nicholas said the increase in frontal alpha power that occurs as a result of pre-sleep drinking likely reflects a disruption of the normal properties of NREM slow wave sleep.
“Similar increases in alpha-delta activity, which are associated with poor or unrefreshing sleep and daytime function, have been observed in individuals with chronic pain conditions,” he said.
“Thus, if sleep is being disrupted regularly by pre-sleep alcohol consumption, particularly over long periods of time, this could have significant detrimental effects on daytime wellbeing and neurocognitive function, such as learning and memory processes.”
Alcohol is not a sleep aid, he noted.
“The take-home message here is that alcohol is not actually a particularly good sleep aid even though it may seem like it helps you get to sleep quicker,” he concluded. “In fact, the quality of the sleep you get is significantly altered and disrupted.”
The study was published in Alcoholism: Clinical & Experimental Research, the journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism.
Source: Wiley Online Library