How Caffeine Affects Your Sleep

When you feel tired during the day, it’s tempting to reach for a quick jolt of energy from a cup of coffee or energy drink. Depending on the time of day, it might also inadvertently disrupt your sleep later that night. Although caffeine undoubtedly provides a boost of energy, its effects are temporary—and, research shows, may interfere with sleep quality. Disrupted sleep, in turn, may lead to more caffeine intake the next day— interrupting your usual cycle of sleep.

Caffeine: Popular for a Reason

Humans have been consuming caffeine for centuries for its ability to stimulate the central nervous system by creating increased feelings of alertness. Recent data from IFIC’s consumer survey of caffeine, finds that approximately nine in ten Americans consume caffeine, and about 75% of caffeine users have caffeine at least once a day. Caffeine is a popular choice among millions of adults because it can boost mental alertness and potentially enhance productivity. People who are physically active also frequently find that caffeine can help prolong endurance[1] and enhance concentration, making caffeine a popular ergogenic aid[2].

Although a moderate amount of caffeine (up to 400 milligrams per day or 4 8 oz. cups of home brewed coffee) is considered to be safe for the healthy adults, it can be difficult to fully quantify caffeine intake, since small amounts of caffeine can be found across many beverages, food, medications, and supplements that anyone might consume in one day. Additionally, caffeinated products like energy shots have become increasingly popular pick-me-ups and come with a particularly high dose of caffeine (>200 mg per serving). People also have varying sensitivities to caffeine. Some people feel the effects of caffeine more rapidly and intensely, and others may have a milder reaction and are able to tolerate greater doses without adverse effects. There are also notable individual differences in the body’s ability to process and metabolize caffeine—another factor that can impact sleep quality.

Sleep: The Basics

While it’s well-known that caffeine’s popularity is on the rise, rather than asking why caffeine consumption has gone up, we might ask another question: Why are people feeling so tired in the first place? An estimated one in three adults in the United States aren’t meeting the National Institute of Healths sleep recommendations of seven to nine hours of shut-eye per night. Getting enough sleep is an important part of a healthy lifestyle because of sleep’s connection to physical and mental health. According to the American Heart Association (AHA), sleep deficiency has been linked to an increased risk of cardiovascular disease, cognitive decline, depression, excess body fat, high blood pressure, and more. Sleep duration and consistency is becoming a key area in health research, so understanding how to optimize sleep can have widespread effects on overall health—and help us make better informed nutritional choices.

Sleep can be classified into two basic types: rapid eye movement (REM) sleep and non-REM sleep[3]. Non-REM sleep has three stages, and each is connected to certain brain waves and neuronal activity:

Stage 1 non-REM sleep: Lasts a few minutes and occurs when the body goes from wakefulness to sleep.
Stage 2 non-REM sleep: Refers to a period of light sleep before deeper sleep.
Stage 3 non-REM sleep: Refers to the period of deep sleep.

REM sleep takes place about every 90 minutes and is known as the period of sleep when dreaming likely occurs. In REM sleep, eyes move around randomly behind eyelids and brain activity looks like an awake period. During sleep, the body cycles through all stages of non-REM and REM sleep several times, and both types of sleep are needed for memory consolidation.

The Effects of Caffeine on Sleep: What the Research Shows

Data suggests most people in the United States aren’t meeting sleep recommendations—and unfortunately, there’s also evidence that caffeine can interfere with REM sleep.

A 2021 study by Weibel, et al. recruited 20 male habitual caffeine consumers to identify the impact of caffeine on their sleep quality. Each participant went through a phase of the trial during which they consumed caffeine, then underwent a caffeine withdrawal, and then were given a placebo. The researchers found that participants reported having the greatest difficulty waking up and feeling more tired when they were consuming caffeine compared with the withdrawal and placebo phases. In further support of this finding, the study also showed that it took longer for participants to reach REM sleep, and that the accumulation of REM sleep proportion was delayed.

Many people think they can erase a poor night of sleep with a morning cup of coffee, but unfortunately, this isn’t the case. Another study by Stepan, et al. investigated the impact of caffeine on sleep deprivation. The researchers found that after a person experiences sleep deprivation, caffeine can help that person with simple attention-related tasks, but the person may still have difficulty completing more-challenging tasks. While caffeine may temporarily help a person with staying awake and performing easy tasks, it isn’t able to mask the effects of sleep deprivation on more complex procedural errors, thus potentially impairing performance on higher-level tasks such as driving. The findings from this research support the essentiality of achieving sufficient sleep duration and quality—a lack of which caffeine, despite its promised boost of temporary alertness, cannot fix.

Caffeine, Sleep, and You: Maintaining the Balance

The utility of caffeine isn’t going away any time soon, but you can decide for yourself how to better utilize it. Before starting a “caffeine routine” or continuing an existing one, it’s important to know what amount of caffeine is right for you. To estimate much caffeine you’re currently consuming, consider using a tool like this caffeine calculator. If you’re consuming above the recommendation of 400 milligrams or less a day, identify which daily sources of caffeine you can reduce. Consuming caffeine above the recommendation can increase chances of its adverse effects, which include increased heart rate, dizziness, fever, and more.

It’s also important to remember that the greater your caffeine intake, the greater the likelihood of caffeine disrupting your sleep quality. Instead of ramping up your caffeine to feel awake, try prioritizing sleep duration and quality to help reduce tiredness. Achieving recommended amounts of sleep is linked to improved mood, better cognitive function, and decreased risk of chronic disease. Before going for caffeine to combat an afternoon lull, try creating a better sleep routine to improve your sleep hygiene. This includes setting a bedtime alarm to give yourself enough time for adequate sleep duration and developing a nighttime routine to help improve your sleep quality—such as putting away electronic devices at least one hour before lights out, engaging in a relaxing activity, like reading, and focusing on healthy nighttime practices like hydrating and brushing your teeth.

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This article was written by Debbie Fetter, PhD.