How Does Coffee Affect Sleep?

Coffee for centuries has been traded around the world for its rich flavors and its ability to increase mental alertness. Caffeine is the main cause and chemical for feeling focused and wired shortly after consuming it.   

What Does Caffeine Do?

Caffeine stimulates your central nervous system which contains the brain and the spinal cord. I works to process sensory information and is the source of thoughts, emotions, memories, all the brain activity. In this way, as a stimulant, caffeine keeps your brain “on” and ready for productivity, alertness, or just staying awake. 

[Editor’s Note. We recently published a detailed Ethiopian coffee guide here. Enjoy!]

To compare coffee to other caffeine drinks, an average cup of green tea has about 25mg of caffeine and black tea has about 50mg, according to the Mayo Clinic. On the other hand, or in the other mug, an average cup of coffee has anywhere between 95-160mgs of caffeine, according to the Mayo Clinic.   

What is the Recommended Amount of Coffee to Consume?

A good rule of thumb is to never consume more than 400mg of caffeine a day to prevent any of the negative effects of coffee. Too much caffeine can lead to nausea, increased heart rates and breathing rates, muscle tremors, and diarrhea.

With that much possible caffeine in a cup of coffee, it isn’t hard to break a threshold of caffeine tolerance that can make your body and stomach ache. 

The Side Effect to Caffeine

Worst of all, caffeine makes it difficult to fall asleep and stay asleep. Coffee is mostly a mental stimulant and stays in your system anywhere from 4 to 6 hours, depending if you are a regular drinker or if you drink it occasionally. Caffeine before bed both makes it more difficult to fall asleep and more likely to wake up during the night.

Research on Coffee and Sleep Disorders

The Henry Ford Hospital’s Sleep Disorders and Research Center in Detroit conducted a study to test caffeine effects on sleep when taken 0, 3, and 6 hours before going to bed.

Based on participant diaries and objective sleep measures, “sleep fragmentation” became a common characteristic of caffeine at night, where they wake up frequently for brief amounts of time.

When consumed at bedtime and 3 hours before bedtime, results report a reduced total sleep time. And even when caffeine is taken 6 hours before bed, it reduced sleep by more than 1 hour. 

Another study on “shift work sleep disorder” describes people who work late hours usually during typical sleeping periods showed that coffee affects their general sleep rhythm. They often struggle with insomnia and excessive sleepiness.

In short, there is little to no mental alertness. Caffeine, however, improves the performance of those who work late shifts. This suggests that caffeine can work as an artificial nap or rest, giving them the mental energy, they need to complete their tasks. 

Both studies in conversation explain that your body will resist sleep with heavy doses of caffeine, particularly around regular times of sleep. There is, however, a lot more research to be done on coffee and sleep, like someone’s personal caffeine sensitivity, or particularly between people with and without insomnia.

Until more research is conducted and released, it is best to keep your cup of coffee (or two) a morning ritual, if you want a good night’s rest.