Late lie-in sets body clock back

Sarah Rainey

IT’S 3.21am on Saturday. The digits on the alarm clock cast an acid-green glow over the room, and the music from the bar I left four hours earlier is still resonating in my ears.

As I twist and turn, only one thought sustains me as I yearn for sleep: at least I can have a lie-in in the morning.

Sleeping in is a guilty pleasure of the weekend – a couple of luxurious extra hours in bed to help us catch up on sleep lost during the working week.

But according to a new study, sleeping in does not help us feel more awake. It does not boost our energy levels. In fact, it disrupts the body’s internal clock so much that just a few extra hours make us feel even more tired than normal on Monday morning.

Researchers at the University of Texas Southwestern Medical Centre found that “sleep debt” built up during the week can only be recovered by going to bed eight hours before our usual wake-up time – and not by going to bed later and getting up later.

The circadian cycle, which controls our body clock, can be completely offset by a change in sleep pattern (like a late night or lying in), making it difficult to get to sleep on Sunday night and even harder to wake up the next day.

It can take a few days before the balance is reset by returning to our regular sleep schedule.

“No one wants to miss opportunities for social activities on Friday and Saturday, so they use Saturday and Sunday mornings to rest up,” the sleep medicine specialist who led the study, Dr Gregory Carter, said.

“Indeed, we feel better after those lie-ins. However, we have delayed our internal clock by up to two hours, making Monday morning a groggy mess. If we sleep longer, our sleep becomes less efficient, we spend more time sleeping lightly, rather than [in] restorative sleep.”

It is something of a relief that scientists have come up with a reason why many of us feel tired during the week, no matter how much extra sleep we have indulged in at weekends. – The Daily Telegraph

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