Around two to four percent of Americans suffer from called obstructive sleep apnea (OSA), a breathing disorder in which the upper air passage (i.e. the pharynx, located at the back of the mouth) narrows or closes during sleep. This results in interrupted breathing (i.e. apnea), which wakens the person, who then resumes breathing and returns to sleep. This can happen hundreds of times each night, significantly reducing sleep time and resulting in daytime sleepiness.

People who drink too much appear to be at increased risk for sleep apnea, especially if they snore. Moderate to high amounts of alcohol drunk in the evening can lead to narrowing of the air passage, causing episodes of apnea even when people do not have an existing apnea condition. The combination of alcohol, OSA, and snoring also increases a person's risk for heart attack, arrhythmia, stroke and sudden death.

People with severe OSA must be extremely careful when drinking. Patients with severe OSA who consume two or more alcoholic drinks per day have been shown to have a fivefold increased risk for fatigue-related traffic crashes compared with OSA patients who consume little or no alcohol.

Alcoholism causes several sleep problems, from frequent awakenings, to poorer sleep quality, to an increase in the time it takes to fall asleep. Perhaps the hardest problem to cope with is the insomnia that can occur when heavy drinking is abruptly reduced and alcohol withdrawal symptoms set in. However, the health benefits of stopping heavy drinking still outweigh this problem. Increased REM sleep may also be related to the hallucinations that sometimes occur during  the process withdrawal. 

Despite some improvement after withdrawal subsides, sleep patterns may never return to normal in those with alcoholism, even after years of abstinence.

Not getting enough sleep is bad in anyone’s books, but combined with alcohol consumption, the effects can be much worse. Studies show that even low doses of alcohol combined with a night of reduced sleep leads to poorer driving performance, even when no alcohol is left in the body. The likelihood of traffic accidents is therefore increased. Reduced alertness can also increase alcohol's sedating effect in situations such as rotating sleep-wake schedules (e.g. shift work) and rapid travel across multiple time zones (i.e. jet lag) .

The effects of alcohol and sleep disturbance can particularly affect the elderly. The same amount of alcohol consumed by an elderly person leads to higher levels of alcohol in the blood and brain than for younger people, and thus, worse effects. Bedtime alcohol consumption among older people may also lead to unsteadiness if walking is attempted during the night, increasing the risk of falls and injuries.