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. The red dot on my BlackBerry is blinking, while an unread message lights up my iPhone screen. 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. But according to a new study, sleeping in doesn't help us feel more awake. It doesn't boost our energy levels. In fact, it has the opposite effect. It disrupts the body's internal clock so much that just a few extra hours makes 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 (such as a late night or lying in), making it difficult to get to sleep on Sunday night and even harder to wake up for work the next day.
No-one wants to miss opportunities for social activities on Friday and Saturday, "so they use Saturday and Sunday mornings to rest up", says Gregory Carter, the sleep medicine specialist who led the study. "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.
"We spend more time sleeping lightly, rather than experiencing restorative sleep [also known as REM - rapid eye movement - sleep, when our body is at its most relaxed]."
It's something of a relief that scientists have come up with a biological reason why many of us feel tired during the week, no matter how much extra sleep we've indulged in at weekends.
So why are we unable to switch off? A new study by the Lighting Research Centre, in New York, identified how exposure to certain types of light can disrupt our sleep. Researchers confirmed that "blue light" from the screens of smartphones, tablet computers and e-readers is particularly detrimental. It suppresses melatonin, a hormone our brains produce during the hours of darkness, which tricks us into thinking it is daytime and makes us feel more alert.
Steven Lockley, assistant professor of Medicine at Harvard University, says: "You should never take a laptop or mobile phone to bed, as the quality of sleep you have afterwards will leave you tired the next day."
Dr Carter's study also confirmed that checking emails at night makes us tired. He adds: "Blue light has an alerting effect." Age, environment and diet can also affect the quality of our rest. Poor sleep can be caused by medical factors such as anxiety or depression, food and drink such as caffeine or alcohol, and physical triggers such as a hot room.
As well as tiredness and mood swings, insomniacs suffer from a range of physical conditions. Sleeping fewer than six hours a night can put us at risk of high blood pressure, stroke, diabetes and heart disease.
The psychological impact can be even more extreme. Dr Stanley Coren, professor of psychology at the University of British Columbia, claims we lose one IQ point for every hour of sleep lost the night before. Lack of sleep is thought to suppress the immune system, making us vulnerable to infection and metabolic changes that can speed up ageing.
A huge "sleep industry" has developed, that has created hundreds of products and gadgets designed to improve our nightly routines. So can any of the quick fixes help beat tiredness?
Sleeping pills are the most common remedy for insomnia. However, they can cause side- effects such as memory problems and daytime grogginess.
Experts remain doubtful of the long-term effects of pills. Professor Lockley says: "People trying to find an easy solution in a pill, rather than the more difficult solution of changing their lifestyle, will be disappointed."
Relaxation training has been shown to minimise thoughts that disturb sleep, while stimulus- control therapy uses props and visual triggers to help sleepers associate their bedrooms with nothing but rest. Yet the treatment is rarely available to insomniacs.
Some frustrated consumers have resorted to alternatives, from reflexology sleep patches to aromatherapy treatments such as scented pillow sprays and room mist.
In the long term, says Professor Lockley, the most effective remedy for sleeplessness is the old- fashioned one: a comfortable bed, firm pillow and a cool, dark room that for most people will induce sleep in no time.
- © Fairfax NZ News
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