Caffeine is the most widely used drug in the world. Coffee, tea, yerba mate, and other caffeine-containing beverages are consumed by the vast majority of people as part of their daily routine. Caffeinated beverages aren’t just tasty — they’re major productivity boosters that have important effects on our health.

In moderation, there’s nothing wrong with getting your caffeine fix. When paired with other beneficial health habits, caffeine intake can be an incredible way to boost your physical and mental health, wellness, and work output. Your daily trip to Starbucks can be considered part of your self-care.

But as with most things, timing matters. Properly-timed caffeine intake can work wonders. But mistimed caffeine intake can have undesirable consequences for a significant aspect of health: sleep. Without proper sleep, we can’t function as we should. For this reason, it’s essential to know how and why caffeine impacts sleep.

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Caffeine, performance, and health

The performance-enhancing effects of caffeine are indisputable. As far as physical performance is concerned, caffeine can improve aerobic endurance, power output, speed, and strength. It may even help to boost fat-burning during exercise.

Caffeine can also improve reaction time, enhance memory, and increase the speed of our brain’s neural circuitry. Caffeine allows us to think faster, more clearly, and more accurately. It’s the best nootropic (“smart drug”) out there.

There are also several health-boosting effects associated with caffeine. Caffeine may reduce the risk of developing neurodegenerative conditions, including Alzheimer’s disease and dementia. There have also been numerous studies linking coffee intake to a reduced risk for cardiovascular disease and death. Drinking up to 3–6 cups per day seems to be associated with the lowest risk. No complaints from us!

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Effects of caffeine on alertness

To understand caffeine’s impact on sleep, we need to become familiar with some basic mechanisms of how caffeine works.

Caffeine is an adenosine antagonist. This means that it binds to adenosine receptors in the brain, blocking adenosine from binding. When adenosine binds to adenosine receptors, it makes us sleepy, less alert, and less energetic. As adenosine levels accumulate throughout the day, we become more tired, eventually reaching a point (hopefully right around bedtime) when levels peak and we fall asleep. By blocking adenosine from binding to adenosine receptors, caffeine has a pro-energetic or energy-giving effect on the body.

But we aren’t really creating more energy when we consume caffeine. Rather, we’re “borrowing” energy. Adenosine builds up during the day even when we have caffeine — its effects are just inhibited while caffeine is in our system. Thus, caffeine intake simply postpones the effects of adenosine. For this reason, when we drink caffeine during the day can have a dramatic impact not only on our sleep, but also on our energy and sleepiness during the day.

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The afternoon crash

Many people wake up and immediately turn to coffee or another caffeine source to jolt themselves awake for work or to power up for a morning workout. This immediate ingestion of caffeine, however, may make us lethargic later in the day. When the caffeine starts to wear off mid-afternoon, our energy levels will begin to drop. To prevent that, we will either need to have more caffeine or to take a nap. It’s important to remember, however, that the afternoon dip in alertness and wakefulness is a natural part of our body’s circadian rhythm, and might not all be the result of caffeine, exercise, or how much sleep we got the previous night.

Could delaying your caffeine intake benefit afternoon alertness? Perhaps. 

When we wake up in the morning, our bodies are primed for alertness. Adenosine levels are low, and cortisol -- a hormone that promotes energy and alertness -- begins to increase. Cortisol also helps to clear out adenosine in the few hours after waking, further enhancing alertness. By delaying caffeine intake, we allow our body’s natural alertness-promoting systems to work their magic. In this way, having the first sip of coffee about 90 minutes or so after waking up will build rather than suppress our already high wakefulness levels, which is what happens when we have caffeine too early.

The effects of delaying caffeine intake are thus two-fold. First, by promoting the body’s optimal patterns of adenosine and cortisol, we leverage natural morning alertness. Second, by preventing the afternoon crash, we reduce the need to have more caffeine later on in the day. This can have profound effects on sleep later that night — a topic we discuss next.

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Afternoon caffeine and sleep

We’ve already described how by blocking the binding of adenosine to adenosine receptors in the brain, caffeine promotes alertness and reduces sleepiness. This is great when we need to be awake. But it’s not ideal when we need to wind down for the night. In order to fall asleep and stay asleep, we need adenosine to bind to adenosine receptors.

Consuming caffeine too close to bedtime has profound effects on all aspects of sleep, including quantity, quality, and architecture (the time spent in various stages and the pattern of our sleep stages). Some people claim that they can have a few shots of espresso after dinner and fall asleep just fine, but in reality, they’re not getting the quality sleep they need. Most aspects of sleep are impaired under the influence of caffeine.

For how long should you avoid caffeine before sleep? Some suggest that 8-12 hours would be ideal. Though this might seem excessive, we need to go this long without caffeine to ensure that all of the caffeine is out of our system before bed. The half-life of caffeine — how long it takes the body to reduce the concentration of caffeine by 50% — is around 4 hours. 

In other words, if you consume 200mg of caffeine around 4pm, you still have 100mg present in your system at 8pm, and 50 mg present at midnight. 

This residual caffeine can impair the early stages of our sleep. Among other things, it can reduce slow wave (deep) and rapid eye movement (REM) sleep. These two sleep stages are crucial for growth hormone release and memory consolidation, as well as for a variety of other important biological processes.

Thus, from a sleep standpoint, it would be ideal to limit or completely avoid caffeine intake at least 8-12 hours before you plan to go to bed.

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The caffeine nap: a tool to optimize mental and physical performance

Everyone feels good after a quick power nap. Could strategically pairing a cup of coffee with your nap be a performance hack? This tool — known as the “caffeine nap” — hasn’t been investigated extensively, but it could be worth trying out. Here’s how it works. 

Consume some caffeine about 10-15 minutes before lying down for a nap. Then, nap for about 20-30 minutes. Right around the time your nap ends, caffeine levels in your body should be peaking. In this scenario, the energy-promoting effects of the nap are stacked onto the alertness-promoting effects of caffeine. Some people find this strategy to work well, while for others, napping after drinking coffee just isn’t going to happen. There’s also the risk that if you “caffeine nap” too late into the afternoon, your sleep later in the evening may be compromised. For this reason, you might want to experiment with different nap times, nap lengths, and doses of caffeine to find out what works best for you. 

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Finding your optimal time to consume caffeine with Basis

With Basis, there’s no need to guess how the timing of your caffeine impacts your sleep. Basis can work that out for you. 

The Basis app tracks your energy levels, which represent the peaks and valleys in your mental and physical energy throughout the day. By analyzing these, Basis can determine when would be the optimal time for you to have caffeine to boost performance while minimizing its impact on your sleep. You’ll even get a “final call” notification for caffeine each day, the time at which it’d be best to limit or stop your caffeine intake for the day.

By tracking your caffeine consumption with the “log activity” feature on Basis, you can also see how your caffeine intake and caffeine timing impact your sleep and energy levels. There’s no better way to make modifications and perfect your health routine than with real-time feedback.

We are now beginning to fully understand the science of timing as it relates to health and performance. This is a renaissance era where wearable health data can help us optimize every aspect of our lives — even our daily coffee ritual.

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