Alcohol can have a sedative effect because alcohol is broken down quite quickly in the body, which leads to a withdrawal effect in the second half of the night. This means that alcohol can put people to sleep at the beginning of the night due to its early sedative effect, but in the second half of the night it leads to restlessness, frequent awakenings and poor sleep quality. In addition, alcohol can increase fatigue and worsen mood the next day.
Alcohol also affects the underlying sleep architecture. Even during the first half of the night, when people feel that alcohol is causing them to fall asleep and they are unaware of their surroundings, beneath the surface the natural sleep pattern is disrupted.
Alcohol reduces the amount of rapid eye movement (REM) sleep and increases alpha or fast wave activity during sleep. While it can increase slow wave sleep, which is normally restful, the concomitant increase in alpha activity leads to alpha-delta sleep, which is not restful. This type of sleep occurs in other conditions where sleep is not restful, such as pain or chronic illness.
SleepHub: What effect does alcohol have on sleep?
