For individuals who drink before sleeping, alcohol initially acts as a sedative -- marked by the delta frequency electroencephalogram (EEG) activity of Slow Wave Sleep (SWS) -- but is later associated with sleep disruption.
Significant reductions in EEG delta frequency activity and power also occur with normal development between the ages of 12 and 16; likewise this is a time when alcohol is commonly consumed for the first time, with dramatic increases in drinking occurring among collage-age individuals. A study of the effects of alcohol on sleep EEG power spectra in college students has found that pre-sleep drinking not only causes an initial increase in SWS-related delta power but also causes an increase in frontal alpha power, which is thought to reflect disturbed sleep.
Results will be published in the February 2015 online-only issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.
"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, National Health & Medical Research Council Peter Doherty Research Fellow in the Sleep Research Laboratory at The University of Melbourne as well as 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," said Nicholas. "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."
Nicholas and his colleagues recruited 24 participants (12 female, 12 male), healthy 18- to 21-year-old social drinkers who had consumed less than seven standard drinks per week during the previous 30 days. Each participant underwent two conditions: pre-sleep alcohol as well as a placebo, followed by standard polysomnography with comprehensive EEG recordings.
Results showed that alcohol increased SWS delta power during NREM. However, there was a simultaneous increase in frontal alpha power.