Caffeine, Alcohol, Nicotine and Sleep

The short version

Caffeine and nicotine are stimulants, and both can interfere with sleep. [1] Alcohol may help you fall asleep but tends to make the rest of the night lighter and more broken. [2] Timing and amounts matter, and people differ in how sensitive they are.

Caffeine

What the research found. In a randomized home study, a fixed 400 mg dose of caffeine taken at bedtime, 3 hours before bedtime or 6 hours before bedtime each disrupted sleep compared with placebo, and the authors concluded that caffeine 6 hours before bed has important disruptive effects. [3] This is a study amount in a single trial, not a personal limit.

What agencies advise. The NHLBI says caffeine effects can last up to 8 hours, so a coffee in the late afternoon can make it hard to fall asleep at night. [1] The NHS advises not smoking or drinking alcohol, tea or coffee at least 6 hours before bed. [4] For restless legs, the NHS suggests no caffeine after midday. [5]

Where caffeine hides. Coffee, tea and chocolate are known sources; it can also be in products you may not expect. [6] The FDA lists typical amounts per 12 fluid ounces: caffeinated soft drinks 23 to 83 mg, green tea 37 mg, black tea 71 mg, brewed coffee 113 to 247 mg, and energy drinks 41 to 246 mg. [6] For most adults the FDA cites 400 mg a day as an amount not generally associated with negative effects, but people vary widely in sensitivity and in how fast they clear caffeine. [6]

Children and teens. Too much caffeine in children and teens can cause a faster heart rate, palpitations, high blood pressure, anxiety and sleep problems, and medical experts advise against energy drinks for them. [6] See Coffee and Black tea for food profiles.

Alcohol

• A drink may make it easier to fall asleep, but sleep tends to be lighter than normal, making night waking more likely. [2]
• The NHS advises avoiding alcohol close to bed, and notes that alcohol and nicotine can have disruptive effects on sleep; it suggests avoiding them 1 to 2 hours before bed in its sleep tips. [7]
• Alcohol and snoring or sleep apnea: a meta-analysis of 13 studies with sleep-lab data (279 people) found alcohol was associated with worse snoring, altered sleep stages, more breathing interruptions per hour and lower lowest oxygen levels in people susceptible to snoring and sleep apnea. [8] The NHS also lists drinking too much alcohol as something to avoid with sleep apnea. [9] See Sleep apnea.
• When people stop drinking, withdrawal symptoms can include insomnia. [10] If you drink heavily, ask a doctor before stopping suddenly.
• If melatonin makes you sleepy in the daytime, the NHS says not to drink alcohol, as it will make you feel more tired. [11] The NHS also says not to drink alcohol while taking diphenhydramine, because it raises the risk of side effects. [12]

Nicotine and smoking

The NHLBI names nicotine as a stimulant that can interfere with sleep and advises avoiding it. [1] The NHS includes smoking in its list of things not to do for at least 6 hours before bed and lists nicotine among common causes of insomnia. [4] Proper evidence not found in the sources read for this page on how much vaping or nicotine replacement affects sleep specifically. If you want to quit, a GP can help. [13]

Practical ideas

• Move caffeine earlier in the day and watch for hidden sources.
• Keep alcohol well away from bedtime, and track your sleep in a diary to see the effect on you. [14]
• Link to other habits in Sleep hygiene and How to fall asleep faster.

When to get help

Seek advice if you rely on alcohol or caffeine to sleep or stay awake, or if sleep problems continue. [4] A GP can help with drinking, smoking or drug use that affects sleep. [13]