Summary: Frequent caffeine consumption reduces gray matter volume in areas of the right medial temporal lobe, including the hippocampus. Ten days of “caffeine abstinence” helps regenerate gray matter.
Source: University of Basel
Coffee, cola or an energy drink: caffeine is the world’s most widely consumed psychoactive substance. Researchers from the University of Basel have now shown in a study that regular caffeine intake can change the gray matter of the brain. However, the effect appears to be temporary.
No question – caffeine helps most of us to feel more alert. However, it can disrupt our sleep if consumed in the evening. Sleep deprivation can in turn affect the gray matter of the brain, as previous studies have shown. So can regular caffeine consumption affect brain structure due to poor sleep? A research team led by Dr. Carolin Reichert and Professor Christian Cajochen of the University of Basel and UPK (the Psychiatric Hospital of the University of Basel) investigated this question in a study.
The result was surprising: the caffeine consumed as part of the study did not result in poor sleep. However, the researchers observed changes in the gray matter, as they report in the journal Cerebral Cortex. Gray matter refers to the parts of the central nervous system made up primarily of the cell bodies of nerve cells, while white matter mainly comprises the neural pathways, the long extensions of the nerve cells.
A group of 20 healthy young individuals, all of whom regularly drink coffee on a daily basis, took part in the study. They were given tablets to take over two 10-day periods, and were asked not to consume any other caffeine during this time. During one study period, they received tablets with caffeine; in the other, tablets with no active ingredient (placebo). At the end of each 10-day period, the researchers examined the volume of the subjects’ gray matter by means of brain scans. They also investigated the participants’ sleep quality in the sleep laboratory by recording the electrical activity of the brain (EEG).
Sleep unaffected, but not gray matter
Data comparison revealed that the participants’ depth of sleep was equal, regardless of whether they had taken the caffeine or the placebo capsules. But they saw a significant difference in the gray matter, depending on whether the subject had received caffeine or the placebo. After 10 days of placebo – i.e. “caffeine abstinence” – the volume of gray matter was greater than following the same period of time with caffeine capsules.
The difference was particularly striking in the right medial temporal lobe, including the hippocampus, a region of the brain that is essential to memory consolidation.
“Our results do not necessarily mean that caffeine consumption has a negative impact on the brain,” emphasizes Reichert.
“But daily caffeine consumption evidently affects our cognitive hardware, which in itself should give rise to further studies.” She adds that in the past, the health effects of caffeine have been investigated primarily in patients, but there is also a need for research on healthy subjects.
Although caffeine appears to reduce the volume of gray matter, after just 10 days of coffee abstinence it had significantly regenerated in the test subjects. “The changes in brain morphology seem to be temporary, but systematic comparisons between coffee drinkers and those who usually consume little or no caffeine have so far been lacking,” says Reichert.
Daily Caffeine Intake Induces Concentration-Dependent Medial Temporal Plasticity in Humans: A Multimodal Double-Blind Randomized Controlled Trial
Caffeine is commonly used to combat high sleep pressure on a daily basis. However, interference with sleep–wake regulation could disturb neural homeostasis and insufficient sleep could lead to alterations in human gray matter. Hence, in this double-blind, randomized, cross-over study, we examined the impact of 10-day caffeine (3 × 150 mg/day) on human gray matter volumes (GMVs) and cerebral blood flow (CBF) by fMRI MP-RAGE and arterial spin-labeling sequences in 20 habitual caffeine consumers, compared with 10-day placebo (3 × 150 mg/day). Sleep pressure was quantified by electroencephalographic slow-wave activity (SWA) in the previous nighttime sleep. Nonparametric voxel-based analyses revealed a significant reduction in GMV in the medial temporal lobe (mTL) after 10 days of caffeine intake compared with 10 days of placebo, voxel-wisely adjusted for CBF considering the decreased perfusion after caffeine intake compared with placebo. Larger GMV reductions were associated with higher individual concentrations of caffeine and paraxanthine. Sleep SWA was, however, neither different between conditions nor associated with caffeine-induced GMV reductions. Therefore, the data do not suggest a link between sleep depth during daily caffeine intake and changes in brain morphology. In conclusion, daily caffeine intake might induce neural plasticity in the mTL depending on individual metabolic processes.