Yes, as a young man, A coffee after dinner in a pizzeria could keep you awake all night; with age, (maybe) you can also take it before sleeping and continue having sweet dreams. A study published in Nature Communications Biology by researchers from the University of Montreal, led by Philipp Thölke, explains why. It does so by studying brain activity during sleep through an electroencephalogram managed by artificial intelligence (AI).
Adenosine
Caffeine acts on the brain receptors of the adenosine neurotransmitter, which is involved in the induction of the dream of slow waves, namely Theta and Alpha waves, which occur between 4 and 7.5 hertz. These waves characterize the initial sleep phase, called Non-REM (NREM) sleep, which is differentiated from the REM phase, where actual dreams occur.
The Non-REM sleep phase is crucial for cognitive memory consolidation and overall well-being, comprising four progressive stages of sleep: the first involves light sleep, the second relaxation of muscles with decreasing consciousness, the third ensues leading to a deep, reparative final stage.
However, as demonstrated by Canadian researchers, the density of adenosine brain receptors decreases with age. Therefore, between the ages of 41 and 58, caffeine does not exert the same potent effect on the body as it does for younger individuals (20-27 years). The inhibitory action of caffeine concerning sleep induction becomes weaker as one matures.
Architecture
The story does not end here; the interpretation of brain activity detected by electroencephalogram through AI indicates not only a different stimulation of receptors but also a different action on sleep architecture.
To grasp this, one must understand that the sleep cycle has a precise series of phases occurring cyclically and with specific frequency waves. Typically, there are four to six different sleep cycles each night, averaging about 90 minutes each.
Dreams
The Non-REM sleep phase, which starts light and then deepens, follows the REM phase of dreams. REM stands for Rapid Eye Movements, referring to the rapid eye movements that occur during sleep as our eyes track the scenes of our dreams. The NREM phase is devoid of actual dreaming processes. This cycle repeats until we awaken.
Entropy
Generally, these sleep cycles maintain a delicate balance with one another, a balance that trends toward increased disorder. This phenomenon is termed Morphic Untropia, indicating how sleep architecture tends to become progressively more complex and less organized with age.
While awake, caffeine increases the functional complexity of brain networks, enhancing our reactivity and preparedness. During sleep, however, it induces an increase in brain activity complexity resembling natural changes associated with aging.
A Drop in an Agitated Sea
Thus, while a cup of coffee may once have been enough to disrupt the fine balance of sleep architecture in youth, it now acts as a mere drop in an already agitated sea that has been stirred by natural physiological changes. When confronting sleep architecture, just prior to the naturally occurring entropic trends associated with age, the influence of coffee before bedtime becomes increasingly negligible.
In fact, aging alters the dynamics of brain activity during sleep, particularly in Non-REM sleep. “Therefore, caffeine loses its initial impact around middle age,” stated Professor Giuseppe Plazzi, of the University of Modena/Reggio Emilia, the director of the Narcolepsy Center in Bologna and former president of the European Narcolepsy Network and the Italian Association of Sleep Medicine.
When the Brain Remains “Young” (Even in Old Age)
The study subjects underwent tests both three hours and one hour before bed, using special caffeine pills that were compared with placebo pills administered to control subjects, who were not aware of their role. Unlike younger participants, those aged 41 to 58 slept comparably well. Thus, if coffee in the evening does not disrupt sleep from a certain age, it signifies that your brain remains “young.”