Summary
Things you should know:
- Limit the amount of caffeine you consume and avoid it for at least 4 hours before going to sleep.
- Caffeine may make it difficult to fall asleep and may also cause you to sleep more lightly.
- A healthy, balanced diet will improve your energy levels and sleep. Having meals at the same time each day will help keep your body clock stable.
- Allow 2-3 hours between the last main meal of the day and going to bed. A small bedtime snack is fine.
- Avoid alcohol for at least 4 hours before bedtime.
- Nicotine may make it more difficult to go to sleep.
How can caffeine affect my sleep?
Caffeine is a stimulant and the most widely consumed psychoactive drug in the world. It is consumed by most Australian adults every day, and is commonly found in beverages and food including tea, coffee, chocolate cola and energy drinks. Caffeine affects sleep in multiple ways:
- It can make it harder to fall asleep (increase sleep latency);
- It can affect sleep architecture through reducing the amount of time that the body spends in slow-wave or ‘deep’ sleep. This affects overall sleep quality and how ‘refreshed’ you feel the next day.
- Given it is a diuretic, caffeine may make you have to get up to go to the toilet more often during the night.
- It can affect your body clock (circadian system). Studies have shown that caffeine taken before bed can delay the body clock, interfering with the normal sleep/wake cycle. This is also why caffeine can help shift the body clock to combat jet-lag associated with changing time zones while travelling.
So, while caffeine’s stimulant effect can make you feel more alert, and even combat tiredness, it ultimately cannot restore sleep deprivation and is not a substitute for a good night’s sleep.
Some people are more sensitive to the effects of caffeine compared with others (due to a combination of how often you have caffeine, the dose you consume, and individual genetic factors). This means the amount of caffeine you can consume, how long it keeps you alert, and how closely you can consume it to sleep without disrupting it varies. Studies have found that caffeine can affect your sleep even when consumed 6 hours prior to .
The amount of caffeine in different sources varies, with regulatory organisations including Food Standards Australia and New Zealand and the Food and Drug Administration (USA) note that up to 400mg of caffeine is generally safe in a healthy adult.
How can food affect my sleep?
Both what you eat in your meals and when you eat them can affect your sleep. As a rule, a healthy, balanced diet will be good for your overall health and well-being. You will have more energy during the day and sleep better at night. It is best if you allow 2-3 hours between having your last main meal of the day and going to bed. You should not go to bed hungry, nor just after you have had a meal. If you have a long time between dinner and bed, you may find that eating a small, light snack (e.g., a piece of fruit) or having a milk drink prior to going to bed helps you to sleep better. Some people find that rich or spicy foods in the evening make it more difficult to sleep well at night.
Will alcohol help my sleep?
Many adults report using alcohol to relax, or as a ‘nightcap’ to help them fall asleep. A survey conducted by the Sleep Health Foundation found that four-in-ten Australian adults had consumed an alcoholic beverage in the hour before sleep, with almost half consuming alcohol a few nights every week. Although alcohol will make you feel sleepy, and may help you fall asleep at night, alcohol will also disrupt your sleep by interfering with sleep architecture (how your body cycles through the normal stages of sleep), resulting in a highly fragmented and disrupted sleep episode causing poor sleep quality, and next day tiredness. Particularly, in the second half of the night, sleep after drinking alcohol is associated with more frequent awakenings, night sweats, nightmares and more frequent awakenings to use the bathroom given alcohol’s diuretic effect. In addition to affecting normal sleep architecture, alcohol also interferes with the body clock, which coordinates the body’s circadian rhythms allowing them to entrain internal processes with the external environment.
It is best to avoid alcohol for at least 3-4 hours before bedtime, however there are many factors that affect how your body metabolises or breaks down alcohol, and therefore some people may need to stop drinking earlier if they are sensitive to the effects of alcohol, or are taking any medications that interact with alcohol which may amplify its effects. It’s also important to note that even modest amounts of alcohol can significantly increase other sleep disorders including snoring and the frequency and intensity of obstructive sleep apnoea (OSA) or restless legs syndrome.
How do cigarettes and vapes affect my sleep?
Cigarettes contain nicotine which is a stimulant used to promote alertness. As such, smoking and vapes can make it harder to fall asleep, and to stay asleep. As with many other drugs, nicotine affects sleep architecture, which results in a disturbed or non-refreshing sleep, which includes more nighttime awakenings. This can make you feel more tired the next day. If you are trying to quit smoking, your sleep may also be impacted, with half of former smokers have trouble sleeping while they’re trying to quit. Stopping smoking is associated with a withdrawal syndrome, which includes changes in mood such as feeling irritable, difficulty concentrating, and poor subsequent sleep. Studies with people using nicotine replacement patches have shown that they may help counteract the disturbed sleep by reducing the number of night awakenings.
Smoking may worsen other sleep symptoms including snoring or sleep apnoea; as well as other conditions that may contribute to poor sleep including coughing or difficulty breathing.
Many vape fluids also contains nicotine, and so vaping has similar effects on sleep to cigarettes. While research on vaping and sleep is beginning to emerge, a 2023 study reported that adolescents who vaped were more likely to report having insufficient sleep (recommended 8 hours on an average school night) compared to those who did not.
Further information:
http://www.webmd.com/sleep-disorders/ss/slideshow-sleep-foods (short slide show)
Sleep Foundation (US) Alcohol and Sleep
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