Just five more minutes … can a coffee before a nap really help you pay back your sleep debt? Credit: www.shutterstock.com
Taking a nap is a common way of overcoming your sleepiness and repaying your sleep debt. Drinking coffee can also help us get through the day. In a 1997 study, 12 sleep-deprived people drank the equivalent of one large cup of brewed coffee and 5 minutes later had the chance to nap for 15 minutes. They then did some driving tests in a simulator to check their alertness. Although drinking a coffee (without a nap) helped their driving performance, combining caffeine with a nap (a coffee nap) improved it even further. People who took a coffee nap were less likely to drift out of their lanes on a 2 hour monotonous simulated drive, compared to when they just drank a coffee (and had no nap) or when they had a decaffeinated coffee (and without a nap).
A coffee nap even helped performance if people dozed during their nap time rather than falling into a deeper sleep. A coffee nap also reduced sleepiness once people got up, with people remaining alert for a couple of hours. However, this early, small study raised many questions. For instance, we don’t know how much coffee the people in the study were used to drinking or if they were what researchers call caffeine-naive and so more likely to experience a greater caffeine “hit”.
How might coffee naps work? When you drink a coffee, the caffeine stays in the stomach for a while before moving to the small intestine. It is from here that caffeine is absorbed and distributed throughout the body. This process, from drinking to absorption, takes 45 minutes. But caffeine’s alerting effect kicks in sooner, about 30minutes after drinking. So, drinking a coffee just before a short nap of less than 15 minutes doesn’t affect the nap as your body hasn’t yet experienced the caffeine hit. Once you wake up from your nap, not only do you experience the hit, your body feels the effects of the caffeine hours later. Although caffeine is broken down in the liver, half of it remains in the blood for 4-5 hours after drinking a moderate amount (equivalent to 2 large cups of brewed coffee). It takes more time to eliminate greater amounts of caffeine from the body.
But if you mis-time your nap, for instance taking it after the caffeine hit and not before, this will mess up your sleep and your performance. This can happen if you wait too long after drinking your coffee before taking your nap.
How much coffee is safe?
While there’s evidence that coffee naps work, are they safe?
If we consider caffeine consumption, 300mg-500mg a day ( 2-3 large cups of brewed coffee) seem safe, as about 70% of caffeine is converted into paraxanthine, which has no apparent toxic effects. But drinking too much caffeine (>500mg a day) can produce symptoms of nervousness, anxiety, irritability, and body effects of restlessness, palpitation, agitation, chills, tremors and increased urine flow.
Food Standards Australia New Zealand says 95mg of caffeine a day (about 2 cans of cola) in children aged 5-12, and 210mg a day (about three cups of instant coffee) in adults increase anxiety levels. If you are drinking too much caffeine and want to stop, withdrawal can cause headache, sleepiness and decreased alertness. So, given the addictive properties of caffeine, “caffeine use disorder” has been classified as “a condition for further study” in the Diagnostic and Statistical Manual of Mental Disorders (DSM-5).
Are coffee naps the best way to pay back sleep debt?
While coffee naps will power you for a couple of hours, they’re not the best way to pay back your sleep debt. Getting enough sleep on most days is a better solution for alertness, performance and productivity. That’s because sleeping is vital for a range of brain and body functions. Getting enough sleep also reduces your risk of a car accident, weight gain, obesity, diabetes and depression. https://theconversation.com/health-check-what-are-coffee-naps-and-can-they-help-you-power-through-the-day-73952
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