For many of us, the morning hasn’t officially begun until we’ve had that first sip of coffee. Whether you prefer your coffee black or over ice, or you’re a seasonal java drinker (PSL lovers, we see you), there’s nothing more euphoric than the smell of freshly ground coffee beans. And while a daily cup of Joe can benefit your health, researchers now warn that consuming too much caffeine while sleep-deprived could actually have a negative impact on your brain.
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Caffeine is a natural substance that promotes alertness by blocking the brain’s adenosine receptors, which are responsible for promoting feelings of sleepiness and tiredness.
It also works quickly: “It reaches a peak level in your blood within 30 to 60 minutes. It has a half-life of three to five hours. The half-life is the time it takes for your body to eliminate half of the drug. The remaining caffeine can stay in your body for a long time,” explains the American Academy of Sleep Medicine (AASM).
So, it's not surprising that 85 percent of Americans consume caffeinated products daily, according to the AASM. However, steadily using caffeine as a crutch to keep you awake can dangerously affect your cognitive abilities.
In a recent study published in the journal Scientific Reports, researchers found that consuming caffeine after a bad night’s sleep could lead to reductions in gray matter volume in the brain.
According to the Cleveland Clinic, gray matter is a special type of tissue in the brain and central nervous system made up of neuronal bodies, axon terminals, and dendrites, which are responsible for sending and receiving electrical signals from other cells. Gray matter controls your body’s movements, memory, and emotions, and it makes up approximately 40 percent of your brain. In other words, gray matter is extremely important, and hurting it could be detrimental to brain health.
For the study, 36 non-smoking participants in the range of 29 years old were split into two groups: caffeine drinkers (CAFF group) and decaffeinated coffee drinkers (DECAF group). Over nine days, participants had two nights with eight hours of sleep, followed by five days of “chronic sleep restriction.” During this phase, the CAFF group consumed 200 milligrams (mg) of caffeine in the morning, followed by 100 mg in the afternoon. The DECAF group received the same amount of decaf coffee.
At the end of the experiment, magnetic resonance imaging (MRI) scans and positron emission tomography (PET) scans showed that the CAFF group experienced a significant decrease in gray matter volume. In contrast, the DECAF group had an increase in gray matter volume despite sleep deprivation.
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“It is commonly known that caffeine intake combats sleepiness. Our data further indicate that caffeine intake also interferes with the brain plasticity induced by sleep loss. However, caffeine does not simply suppress or normalize the gray matter change but also impacts gray matter in an opposite direction. It is unclear how the effect of this brain plasticity manifests on the cognitive behavioral levels; what we know is that it is likely demonstrating the adenosine modulation in neural homeostasis,” the study’s authors told PsyPost.
That said, the researchers did point out that adenosine receptor availability can vary by individual. Those with lower baseline availability showed greater reductions in gray matter volume during the chronic sleep restriction phase.
“People who have a higher A1R availability seem to have more resistance to the effect of caffeine on gray matter,” the researchers explained. “After a recovery sleep and around 30-hour caffeine withdrawal, most of the changes in gray matter have recovered, except the increased dorsolateral prefrontal cortex associated with chronic sleep restriction and the decreased thalamus associated caffeine intake.”
More research is needed to better understand the correlation between reductions in gray matter and sleep deprivation, but caffeine certainly plays a role.
“Although the impact of a total sleep deprivation could not be generalized to chronic sleep restriction, we speculated that the gray matter responses to an increasing duration and/or intensity of sleep loss may not follow a linear trajectory. More studies are certainly warranted to systematically examine the gray matter changes in different patterns of sleep restrictions,” said researchers.
