Caffeine is notorious for decreasing sleep quality. But did you know this is in large part due to caffeine’s half-life of about six hours, which is the amount of time it takes for the body to reduce the amount of active caffeine by half? Even if consumed early in the day or in small quantities, caffeine can reduce the amount of deep sleep you get at night, causing a vicious cycle of poor sleep and tiredness during the day.
Caffeine is a stimulant that in the short term can cause feelings of alertness. However, it can also cause sleep disruption as well as other side effects like anxiety, nervousness, and headaches.
Caffeine has a half life of about six hours, so late day caffeine consumption can significantly disrupt sleep at night.
Sleep studies (polysomnography) show that caffeine reduces slow wave sleep and rapid eye movement (REM) sleep, which are the deep, restorative phases of nighttime sleep.
Limiting caffeine consumption to early in the day (or to even none at all) is beneficial for sleep health.
Caffeine and its origins
Caffeine is bitter tasting substance that occurs naturally in over sixty plants, including:
- Coffee beans;
- Tea leaves;
- Kola nuts (which can flavor sodas);
- Cacao pods (which are used in chocolate products).
Most of the world consumes caffeine in liquid form. In general, a standard 8–12 oz caffeinated beverage can contain anywhere from 14–200 mg of caffeine per serving. Coffee and black teas contain the most caffeine per ounce. There is also synthetic or man-made caffeine which can be added to certain medicines like pain relievers or energy drinks.
Caffeine’s effects on the body
Caffeine acts as a central nervous stimulant and as such can give you a sense of feeling more awake and having more energy. This is why many of us rely on our morning cup of coffee to help us wake up. Caffeine also increases your blood pressure and heart rate and can cause you to produce more urine since it also has diuretic properties. Caffeine has even been found to delay the body’s ability to secrete melatonin, a natural hormone that induces sleepiness in response to darkness, making it difficult to get restful sleep. If you drink too much caffeine, you can experience headaches, anxiety, shakiness, and insomnia.
Caffeine’s half-life – why does it matter?
Caffeine’s half-life is about six hours. This means it takes six hours for the caffeine you consume at any given point to be reduced by half in the body. So, the large cup of coffee you drink at 3:00 pm is only half gone by 9:00 pm when you might be getting ready for bed. Fast forward to 3:00 am, and there still might be a quarter cup of that coffee from twelve hours ago still in your body, negatively impacting your sleep. This is why it is so important to try and limit your caffeine consumption to early in the day as much as possible in the setting of sleep health.
Sleep studies of people who drink caffeine
Studies of patients via polysomnography, or in a sleep lab with brain monitoring, have shown that caffeine consumption even as early as six hours before bedtime can reduce sleep quality as well as, potentially, decrease deep sleep such as REM sleep. These studies also show caffeine causes problems with falling asleep and can even decrease total sleep time at night by up to an hour!
How to adjust your caffeine consumption for better sleep
If you, like many, aren’t quite ready to cut out caffeine completely but have trouble with sleep, there are a few steps you can take to modify your consumption to reduce caffeine’s negative effects.
- Limit your overall intake of caffeine;
- Only consume caffeine in the morning;
- Choose decaffeinated or caffeine free options.
The American Academy of Sleep Medicine recommends no more than 300–400mg of caffeine per day (about three to four 8 oz. cups of coffee) to optimize sleep health. However, please be sure to check with your own physician for an exact caffeine recommendation which can vary depending on whether or not you have other chronic conditions.
If you find yourself struggling with sleep at night, it might be time to think about your caffeine habits. While your daily dose(s) of caffeine may be providing you with a much-needed energy boost, it is important to make sure you are not drinking too much caffeine or having it too late in the day (due to caffeine’s long half-life) to ensure you are not inadvertently disrupting the quality of your sleep at night. Restful sleep is critical for overall health, so if you are finding yourself feeling tired during the day, it might be time to cut out the caffeine to try to break the sleepiness cycle.
- Medline plus. Caffeine.
- American Academy of Sleep Medicine. Sleep and Caffeine.
- Journal of Clinical Sleep Medicine. Caffeine Effects on Sleep Take 0, 3, or 6 Hours before Going to Bed.
- Science Translational Medicine. Effects of caffeine on the human circadian clock in vivo and in vitro.
- Risk Management and Healthcare Policy. Effects of caffeine on sleep quality and daytime functioning.
Show all references
- Journal of Biological Rhythms. Regular Caffeine Intake Delays REM Sleep Promotion and Attenuates Sleep Quality in Healthy Men.