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There is a ritual that many of us follow without questioning it. We arrived at five in the afternoon with our brains fried, we ordered a coffee—or a tea, or a Coca-Cola—and we continued. It’s the push we need to get through the rest of the day. What almost no one knows is that that five o’clock coffee may be sabotaging your eleven o’clock sleep. What we usually do when we don’t sleep well is point to our cell phone, stress, late dinner, or looping thoughts. We rarely point to the cup. And yet, for doctor Pablo Ferrero, a specialist in sleep medicine, the answer is there: “Caffeine is the number one enemy of good rest.” The chemistry behind the problem. To understand why caffeine is so disruptive, you have to know adenosine. It is a substance that the brain accumulates during waking hours and that, when it reaches a certain level, gives us that feeling of tiredness, that it is time to stop. It is, in a certain sense, the biological alarm of sleep. What caffeine does is to block adenosine receptors: Silences the alarm without disabling actual fatigue. The body continues to accumulate fatigue, but the brain stops perceiving it. The problem is not just that it is difficult to fall asleep. It’s what happens inside while we sleep. A study published in the Journal of Clinical Sleep Medicine found that a dose of 400 milligrams of caffeine consumed six hours before bedtime significantly reduced sleep efficiency. Other job in Neuropsychopharmacology was more specific: Consuming caffeine before bed reduces the amount of REM sleep, the phase in which the brain consolidates memories and regulates mood. More in depth. The numbers They are concrete and not very reassuring.: That dose can delay sleep onset by up to 45 minutes and reduce deep sleep—NREM phases 3 and 4—by up to 20%. Taken to everyday practice: if you have a coffee at 5:00 p.m. and go to bed at 11:00 p.m., your deep sleep can go from the usual 120 minutes to just 96. That’s 24 minutes less brain and physical repair. Nightly. But there is something even more disturbing: a scientific review published in the magazine Nutrients concluded that caffeine can reduce deep sleep even when the person sleeps eight hours continuously. That is, it is not enough to add hours. Quality does not always coincide with the perception of having a good rest. You can wake up thinking you’ve had a great night’s sleep while your brain hasn’t gone through the cycles it needed. Time matters. One of the most common mistakes is to think that afternoon coffee “no longer works” because you are used to it. Tolerance reduces the perception of the stimulus, but The half-life of caffeine in the body is between 4 and 9 hours: That means that half of what you drank at three in the afternoon is still active at eleven at night. And the problem is not limited to coffee. Caffeine is also present in some soft drinks, energy drinks, teas and chocolates, something that Ferrero expressly points out as a factor that goes unnoticed. It’s not just the breakfast cup: it’s the entire consumption circuit of the day. The broken clock. Caffeine, however, does not act alone. Ferrero points to another factor that can be even more decisive: schedule disorder. The body works through the circadian rhythman internal biological clock that regulates when we feel sleepy and when we are alert. When schedules constantly change—we go to bed at eleven Monday through Thursday and one o’clock on Fridays and Saturdays, and we get up three hours later on Sunday—that system loses synchronization. science back this up with data: Sleeping at irregular hours can cause insomnia, daytime sleepiness and alter hormone production, metabolism and eating habits, increasing the risk of diseases such as diabetes, obesity and depression. The impact don’t stop feeling tired Since while we sleep, the brain eliminates the beta-amyloid protein, accumulated during wakefulness and directly related to Alzheimer’s and other neurological disorders. Poor sleep is not just a tomorrow’s problem: it is a long-term investment—or debt. The motive is not innocent either. But the mechanism is more precise than is usually explained. The blue light emitted by screens suppresses the production of melatonin, the hormone that signals the brain it’s time to sleep. A study by the Barcelona Institute for Global Health warned that this overexposure directly alters the sleep-wake cycle. Just two hours of exposure to bright screens before bed can reduce melatonin levels by 20% or moreand the time to fall asleep can go from 15 minutes to more than an hour. Using a tablet before going to sleep can delay nighttime sleep by up to 96 minutes; that of a smartphone, up to 67. Harvard Medical School noted that “just a few minutes of screen stimulation can delay the release of melatonin by several hours and desynchronize the biological clock.” The problem is that we live in a society with increasingly irregular patterns: high light exposure at night, changing work schedules, screens until the last minute. We are sending our brain signals that it is still daytime when it is no longer daytime. So what works? Ferrero’s answer is not particularly glamorous, but it is supported by evidence. Going to bed and getting up at similar times every day—even on weekends—is the most basic and most ignored advice. Added to this is a dark, quiet and cool bedroom: artificial light and high temperatures send alert signals to the brain that make it difficult to rest. Avoid screens before going to bed—at least 30 minutes—and have a light dinner, without excess fats or spicy food, close to bedtime. For those who do not have insomnia, a short nap may be beneficial; The key is that it does not exceed 25 minutes so as not to disturb your night’s sleep. And in the face of anxiety or thoughts in a loop, Ferrero points out tools with scientific evidence: … Read more