Too much and too little sleep 'both dangerous'

It's difficult getting a good night's sleep as we juggle the demands of work, family and leisure time.

 Insomnia: sleep your way to a healthier day

Now UK scientists say that cutting our sleeping from seven hours a night - considered the optimal amount for the average adult - to five or less hours a night, could lead to a 1.7 fold increased risk of death.

"Fewer hours of sleep and greater levels of sleep disturbance have become widespread in industrialised societies," said Professor Francesco Cappuccio of the University of Warwick.

"This change, largely the result of sleep curtailment to create more time for leisure and shiftwork, has meant that reports of fatigue, tiredness and excessive daytime sleepiness are more common. Sleep represents the daily process of physiological restitution and recovery, and lack of sleep has far-reaching effects."

More surprisingly, in a study of over 10,000 British civil servants, the researchers found that those individuals who increased the number of hours they slept each night from seven to eight hours or more were more than twice as likely to die as those who kept sleeping for seven.

Professor Cappuccio said that this association has not been investigated but suggested that the causes may include depression, low socioeconomic status or cancer-related fatigue.

He said that adults should aim to sleep around seven hours a night.