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Should you drink coffee at night? (Probably not)

by Mark Miller 6 min read

coffee at night

Café-goers might hold off on the coffee late at night or even in the afternoon as studies have shown caffeine can cause big disruptions to sleep patterns. (Open source image)

Should you drink coffee or take caffeine at night? Apparently not. Between not getting enough sleep and drinking alcohol or doing drugs, many people are not getting enough sleep, and the sleep they do get is not optimal, a study says.

One study says if you drink coffee or take caffeine at night that can interfere with sleep patterns by disrupting the circadian rhythm, or the body's internal clock that regulates when you sleep and stay awake.

Disrupting this vital rhythm may mean you feel less energetic and more sluggish during the day. A 2015 CBS News story [1] reporting on the study says it can feel like jet lag, that phenomenon of red-eyed exhaustion and confusion from overseas travel across many time zones.

CBS said the study needed to be confirmed, and that it didn't explore how the body's clock was disrupted, if at all, by coffee or caffeine consumption during the daytime.

Keeps you awake into the wee hours

Caffeine doesn't just disrupt the circadian rhythm. It can also keep some people awake into the wee hours of the morning.

After all, as we explained in this blog [7], the half-life of caffeine is about 5 or 6 hours. In others, half of the caffeine you consume is still in your body affecting you after 6 hours. One quarter of the caffeine remains after another 6 hours, etc.

Kenneth Wright Jr., a study co-author and researcher quoted by CBS News, said caffeine at night makes you want to sleep in in the morning. Professor Wright is with the University of Colorado at Boulder's Department of Integrative Physiology.

Other studies have found that caffeine may disrupt rhythms of other organisms, including mice, CBS reports. This small, preliminary study, in the journal Science Translational Medicine,tried to explain how caffeine disrupts the body's internal clock.

The study involved just five people, whose reactions to caffeine does before bedtime were analyzed over the course of 49 days. They got a placebo or a capsule of caffeine, adjusted to their body, three hours before their usual bedtime. The amount was small, equivalent to just a double espresso or medium cup of regular coffee for those who got the caffeine at all.

Wright and his colleagues also exposed them to varying brightnesses of light, from bright to dim. Bright light is known to make people desire sleep later because it resets the internal rhythm, CBS says.

While bright light seems to delay the body's internal clock by 80 minutes, the caffeine did so for just half that time, the study found.

The study was small

CBS quoted another professor and sleep researcher, Jamie Seitzer, who was not involved in the study. He said the study holds promise, but the number of subjects was too small to draw conclusions about the general public.

One conclusion that can be drawn is that if you want to get to sleep on time and wake up feeling bright-eyed and bushy-tailed, don't drink coffee before bedtime. But it seems like many people already know that. Others seem to be able to consume caffeine before bedtime, Professor Wright said.

Night owls vs. morning people

Another study, this one involving students at Stanford University in California, studied night owls vs. morning people to see how the world's most popular mood-altering substance (caffeine) affected their sleep.

A story [2] on the study on Jezebel.com states:

The results showed that those students who were morning people and drank caffeine during the day were more likely to wake up in the middle of the night than their night owl counterparts who also consumed caffeine during the day.

In terms of caffeine levels, the more caffeine the morning people had in their bodies, the more time they were awake during the night after an initial period of sleep. But this wasn't true for night owls.

Jamie Zeitzer, who commented for CBS, was actually involved in this study. The Jezebel story says:

The fact that they used college students as their sample makes this slightly unreliable because as we know, they tend to have very poor sleeping habits and are usually sleep deprived since they're always up studying.

But Jamie Zeitzer, one of the researchers, explained that this did have an upside because "it didn't matter how much caffeine they had." They usually had no trouble falling asleep. It was just once they were asleep that the caffeine had an effect.

Dr. Breus tells Dr. Oz that people should avoid caffeine after 2 p.m.

For when you do need caffeine at night

If you do need caffeine to stay up at night, for an all-night study session or if you work the night shift, try Viter Energy Mints [3] with caffeine. If at some point you go to sleep, your bladder won't be full and cause you to go to the bathroom, which is a further disruption to sleep.

Viter Energy Mints [4] also have invigorating B vitamins. And they are sugar-free, so they won't decay your teeth.

If you are in a place where you can't brush your teeth or use mouthwash, the mintiness will cleanse your breath.

When to stop caffeinating

So exactly when should you stop drinking coffee? Another small study involving just 12 subjects analyzed what caffeine did to people drinking it at various times before bedtime.

One conclusion that came out, and this applies to many people, is that you should not consume caffeine too soon before bedtime or even too late in the day.

Huffington Post's Michael J. Breus, the Sleep Doctor, reported on the study [5], which was done by researchers with the Wayne State College of Medicine and the Henry Ford Hospital's Sleep Disorders and Research Center.

The team determined that you shouldn't even take caffeine six hours before bedtime. It disrupts sleep so much that people in the study had their quantity and quality of sleep lessened.

Zero hour before dawn

Subjects were examined for sleep disruption after taking caffeine at zero, three and six hours before bedtime. At all three points, the researchers found, the people's sleep time was significantly reduced. Even at six hours, it was reduced by more than an hour.

Sleep and caffeine

Volunteers recorded in diaries their sleep disruptions for caffeine taken at bedtime and for caffeine taken at three hours before. Sleep monitors measured sleep time for those consuming caffeine six hours before sleeping. These sleep-monitor observations, which found such significant disruption, were important because they confirm people shouldn't try to rely on their own observations of sleep, which may be faulty.

The study suggests that you may think an afternoon cup of java isn't affecting your sleep quantity or quality, but it may actually be doing so.

Caffeine's effects on sleep

The Sleep Foundation explains the effect caffeine has on sleep when it's taken too late in the day [6]:

Caffeine can impact the onset of sleep and reduce sleep time, efficiency, and satisfaction levels. Older adults may also be more susceptible to caffeine-induced sleep troubles. Caffeine notably reduces the time of slow-wave sleep, which is the stage of deep, restful sleep that leaves us feeling refreshed and alert in the morning. Caffeine-interrupted sleep can lead to sleep deprivation the following day, which is characterized by fatigue and problems with learning, memory, problem-solving, and emotion regulation.

Caffeine at night? No (unless you can handle it)

The Huffington Post article recommends cutting off caffeine at 2 in the afternoon and tapering off through the day. Start with your strongest cup first thing in the morning, but have less strong cups later. Also, avoid large drinks that contain a lot of caffeine. Dr. Breus recommends an 8-ounce cup of coffee instead of a jumbo cola or a 20-ounce latte.

So if you know you can handle caffeine and can get a full night's sleep and feel good the next morning, by all means indulge. If you can't, be more judicious and hold off until morning and limit intake in the afternoon.


[1] https://www.cbsnews.com/news/what-drinking-coffee-at-night-does-to-your-body-clock/

[2] https://jezebel.com/caffeine-keeps-morning-people-up-all-night-leaves-nigh-5889862

[3] https://amzn.to/3jb7Gwg

[4] https://www.goviter.com/collections/viter-energy-mints

[5] https://www.huffpost.com/entry/caffeine-sleep_b_4454546

[6] https://www.sleepfoundation.org/nutrition/caffeine-and-sleep

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