Sleep and Caffeine
If you’re using caffeine to stay alertand operate on less sleep, you’re accumulating a sleep debt that will catch up with you
By Richard A. Friedman, MD
Washington Post - May 2023
Recently, a 32-year-old patient of mine told me he had driven to work and fallen asleep behind the wheel at a red light. To his chagrin, he was pulled over by an officer who arrested him on suspicion of driving under the influence of drugs or alcohol. He wasn’t.
It turns out he was driving under the powerful influence of chronic sleep deprivation, which he thought he could keep at bay with ever-increasing amounts of caffeine. Feeling overwhelmed by the grueling pace of his graduate studies and teaching responsibilities, he decided to shave an hour or two off his sleep schedule and rely on coffee to turbocharge himself in the morning.
The strategy worked well at first and he felt energized and alert. He was highly productive and focused for several months before he noticed that his coffee consumption began creeping u
p from one to nearly six cups per day to stay alert on just five hours of sleep each night — two hours short of his regular total.
How caffeine fools your body
An 8-ounce cup of coffee provides about 100 milligrams of caffeine. Between 400 and 500 mg of caffeine per day is generally considered safe. Caffeine toxicity, like seizures or an arrhythmia, is common with consumption of 1200 mg or more per day.
My patient was unaware that his caffeine-induced sense of alertness was illusory. His brain was deeply and chronically deprived of sleep, and it was fooled only temporarily by his hefty caffeine use. The fact is that no known drug, including caffeine, can effectively reverse sleep deprivation.
The reason has to do, in part, with the circadian rhythm of a chemical called adenosine that plays a major role in the regulation of sleep.
When you awake from a restful night of sleep, the adenosine level in your brain is at its nadir. Throughout the day, it steadily rises and gradually produces the pressure to sleep in the evening. During sleep, adenosine is cleared from the brain, which helps us wake up and stay alert.
Caffeine is a powerful antagonist at adenosine receptors in the brain, blocking the sedating effects of adenosine and making you feel stimulated and mentally sharp.
How chronic sleep deprivation develops
Here’s the problem. If you cut short your normal night of sleep, adenosine is not fully cleared from the brain. With chronic sleep deprivation, adenosine levels continue to rise, creating a persistent sense of fatigue and sleepiness and impairing cognitive function.
The brain adapts to this flood of adenosine by increasing the number of adenosine receptors in an attempt to get you to fall asleep, which of course only makes you feel more tired.
You will probably respond by increasing your caffeine consumption, in an attempt to block rising adenosine activity, which can only be restored by a normal night of sleep — the very thing my patient was trying to cut short.
Sleep deprivation doesn’t just make you tired. It impairs the brain’s ability to consolidate memory.
During sleep, your neurons are remodeled and change their firing pattern, which helps burn in the memories that are formed during the day.
Too little sleep can also exacerbate pre-existing depression and anxiety disorders and make people with no previous mental health problems generally more angry and impulsive. One study found that young people who were deprived of sleep for just five days showed an increased response in their amygdala to angry faces compared to their normal baseline state. The amygdala is a brain region critical to the processing of fear and danger.
Intriguingly, while caffeine can’t eradicate sleep deprivation, it does appear to offset some of the harmful cognitive effects of sleep loss on memory. This may be one of the reasons people think caffeine is working for them: Even if caffeine contributes to their chronic sleep deprivation via its alerting effects, they aren’t (yet) experiencing enough adverse cognitive effects of sleep loss to blame caffeine.
The stress-caffeine-sleep-wake cycle
Few of us are champion sleepers. It’s recommended that adults get seven to eight hours a day of sleep; teens need eight to 10 hours a day; and young children need even more. In fact, 1 in 3 Americans report that they don’t get the recommended number of hours of sleep to feel restored and rested — either because they have trouble falling or staying asleep, or they wake up too early.
The stimulation of modern life doesn’t suddenly vanish the moment you close your eyes in bed. Whether it’s ruminating about what happened during the day or worrying about tomorrow, turning off and relaxing takes a little time.
That’s the normal and near universal psychophysiological arousal of everyday life. It’s probably the biggest driving force behind the self-sustaining cycles of morning caffeine and evening alcohol or cannabis, to say nothing about sleeping pills. Sleep medications such as Ambien, Lunesta and Restoril will knock you out but they are best for short-term use — to help deal with unusual stress that makes us very anxious and provokes insomnia.
But these hypnotic medications, which increase the activity of GABA (the brain’s major inhibitory neurotransmitter) and produce a characteristic calm, are potentially habit-forming and addictive. They can also cause adverse cognitive effects, in learning and memory, particularly among older people.
How to break the cycle
Caffeine is usually metabolized within four to six hours, though drinking coffee throughout the day can interfere with sleep and drive the use of sedating drugs to turn off. With just a little effort, you can break this cycle.
Given the average half-life of caffeine, it’s best to keep your coffee drinking to the morning and try to avoid caffeine after lunch. Some people are genetically slow metabolizers of caffeine and will have significant sleep-onset insomnia even from early morning coffee; they should probably stick to tea.
The simple truth is that you cannot keep yourself propped up with caffeine indefinitely because the rising tide of adenosine in your brain will become impossible to ignore. When that happens, don’t panic and turn to sleep medication, just give your brain a chance to turn off naturally.
And here’s the most effective trick for falling asleep, which has been studied and shown to be as effective — if not more — than any hypnotic drug.
Don’t do anything in bed except sleep or have sex — no reading, listening to music or anything else. This is so your brain associates the bed only with sleep.
Set a regular time for sleep. If you’re not asleep in 15 or 20 minutes, get out of bed and go to a comfortable chair or couch and read or watch something that’s not too exciting. As soon as you feel tired, go back to bed and try again. Not asleep in 20 minutes? Repeat this drill until you are.
You might spend the first few nights getting in and out of bed. Even if you only sleep a few hours, your “sleep efficiency” — the amount of time in bed that you’re asleep — will be a staggering 100 percent. You will be on your way to breaking the learned association between your bed and insomnia.