Classes & Events News Get

Does Coffee Really Affect Your Sleep?

July 10, 2023

A tired man gazes thoughtfully at his cup of coffee.

Many of us start our day with a hot cup (or two) of joe. Without it, we’re cranky and sluggish. Some of us continue drinking coffee (or other caffeinated drinks) throughout the day — especially when we need to stay alert. But how is your coffee habit affecting your sleep?

Matthew Epstein, MD, a pulmonologist and sleep medicine doctor with Atlantic Health System and associate director of the Atlantic Health Sleep Centers, explains how the body reacts to coffee and what that means for our sleep quality.

Coffee and Brain Chemistry

The main component of coffee is caffeine, an organic compound that acts as a stimulant on the brain and central nervous system.

If you’re a regular coffee drinker, you know that the caffeine in coffee can make you feel more alert, less sleepy, more energized and less moody. “These benefits are great during the day, but can be problematic at night when we’re trying to wind down,” Dr. Epstein says.

Coffee and Sleep

A quick science lesson: Throughout the day, our bodies produce a chemical called adenosine, which promotes sleepiness. Because adenosine builds up over time, the longer we’re awake, the more adenosine we have and the sleepier we become.

Unfortunately for coffee drinkers, caffeine blocks adenosine receptors and their sleep-inducing effects. In other words, we’re wide awake. Our wired, overstimulated brains make it difficult to fall asleep or stay asleep at night. As a result, our overnight sleep quality suffers and we wake up tired the next day — looking for more coffee to compensate and starting the cycle all over again.

Variables to the Effects of Caffeine

Most sleep specialists recommend cutting off your coffee supply in the early afternoon, around 2 or 3 p.m., or roughly eight hours before you go to bed. But that’s just a guideline. Everyone is different.

How much coffee you drink, what time you drink it and your tolerance level for caffeine all play a role in determining how your body will respond. Some people metabolize caffeine quickly, so a cup of coffee in the afternoon doesn’t affect them the same way it does someone who metabolizes caffeine more slowly.

There is no chemical substitute for getting good, quality sleep.

Matthew Epstein, MD


The Food and Drug Administration says 400 milligrams of caffeine is safe for most healthy adults to consume in a day (that’s about four cups of coffee), but that doesn’t take into consideration how you metabolize it or how it affects your sleep.

Regardless of how well you tolerate caffeine or how little you drink, even a small amount of caffeine will negatively impact your sleep quality.

“Several years ago, a study actually demonstrated subtle disturbances in brainwave activity during overnight sleep following caffeine consumption from the previous morning,” Dr. Epstein says. “And poor sleep comes with a variety of negative consequences — everything from slow reaction times and increased irritability to increased risk for bigger health problems, like heart disease and diabetes.”

So, the best rule of thumb: Limit your consumption, both in quantity and timing.

Dr . Epstein is not telling you to give up your morning coffee, but he does advise cutting back if you rely on it to make up for poor sleep.

“Many of us are sleep deprived,” he says. “We cheat on sleep and try to compensate the next day by drinking lots of coffee or other caffeinated drinks. But there is no chemical substitute for getting good, quality sleep.”

  • Sleep
  • Healthy Living