DESPITE our best intentions, we don鈥檛 always get enough sleep. So what happens when we party until dawn or shave off a couple of hours each night?
The need to sleep is controlled by a two-tier system. The circadian clock relies on light to keep your sleep/wake pattern within around 24 hours. Then there鈥檚 sleep drive or sleep pressure. The longer you are awake, the more a chemical called adenosine builds up in your brain, sending signals that increase your desire for sleep (see diagram). 鈥淎fter 16 hours it should be at a screaming level that means you have to fall asleep,鈥� says , who researches sleep at the University of California, Berkeley. 鈥淲hen you do, the pressure valve is released.鈥�
Caffeine keeps you perky by blocking adenosine receptors in the brain, but the effects of overriding the sleep drive quickly show themselves. Being awake for 24 hours will leave you with the same level of cognitive impairment as having a blood alcohol content of 0.1 per cent 鈥� more than the drink-drive limit in several countries. Chronic lack of sleep takes a toll, too. In one study, researchers followed students who slept just 4 hours a night for six nights in a row. They developed higher blood pressure, increased levels of the stress hormone cortisol and insulin resistance, a precursor to type 2 diabetes. They also produced half the normal number of antibodies in response to a flu vaccination.
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Fortunately, these immediate effects were reversed when the students caught up on the hours of sleep they had lost. So if your sleep pressure is high, the simple solution is to repay the debt as soon as you can with a lie-in or a nap (see 鈥�How to听nap like a pro鈥�). 鈥淵ou certainly can recover from the immediate effects of insufficient sleep by then sleeping longer,鈥� says of the University of Surrey, UK. 鈥淢any of us do it every weekend.鈥�
However, this requires you to recognise you need more sleep, and the more sleep deprived you become, the more you underestimate how tired you actually are. If you are suffering from chronic sleep loss 鈥� after a hectic period of work, for example 鈥� take a proper holiday to break the cycle, says Dijk. 鈥淭hat鈥檚 one way to recalibrate your assessment of what is optimal.鈥�
But there鈥檚 a more serious concern. The jury is still out on whether naps and lie-ins can mitigate the long-term health effects of too little sleep. We know that shift work and jet lag, which mess with our body clock, also cause havoc with our health. Regularly sleeping at the wrong time can lead to diabetes, obesity and cancer, among other problems. Now, it seems, catching up on sleep at the weekend, a phenomenon known as social jet lag, might cause the same kinds of health problems as shift work.
So, although anyone can recover from the short-term effects of the odd white night, a long-term habit of catching up on sleep at the weekends may well catch up with you in the end.
We answer all the questions keeping you up at night in 鈥淪leep: A user鈥檚 guide鈥�
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This article appeared in print under the headline 鈥淐an I catch up on what I miss?鈥�
