New York Times: Alcohol disrupts what’s known as your sleep architecture, the normal phases of deeper and lighter sleep we go through every night.
A night of drinking can “fragment,” or interrupt, these patterns, experts say, and you may wake up several times as you ricochet through the usual stages of sleep.
“You pay for it in the second half of the night,” said Dr. Jennifer Martin, a psychologist and professor of medicine at the University of California, Los Angeles. Alcohol is “initially sedating, but as it’s metabolized, it’s very activating.”
Here’s how it breaks down. In the first half of the night, when fairly high levels of alcohol are still coursing through your bloodstream, you’ll probably sleep deeply and dreamlessly. One reason: In the brain, alcohol acts on gamma-aminobutyric acid, or GABA, a neurotransmitter that inhibits impulses between nerve cells and has a calming effect. Alcohol can also suppress rapid eye movement, or REM sleep, which is when most dreaming occurs.