Kassel, Germany - Even though humans sleep away about one-third of their lives, sleep science is relatively new. But the latest results show that sex trumps sport as a sleeping aid.

These are just some of the results presented at the annual convention of the German Sleep Society (DGSM) in Kassel, central Germany, where 1,500 scientists recently gathered to discuss factors contributing to good and healthy sleep.

"Earlier, people thought that sleeping disorders were the result of other diseases. Today, we know that it's the opposite and many diseases get worse or exist because the patient sleeps poorly," says Geert Mayer, head of the DGSM.

"Cardiological and circulatory problems are often precipitated by unsound sleep lasting for a longer period. We've also established a significant connection between sleeping disorders and diseases like dementia or Parkinson's," added the neurology professor.

According to one study, 69 per cent of Parkinson's patients have had sleeping disorders in the past which often start in childhood.

"About 40 per cent of all small children have sleeping disorders. They usually disappear over time, but it's not unusual for older children to suffer from daytime sleepiness. About one-third of pre-teens and teens are affected," said Alfred Wiater, the head of a paediatrics clinic in Cologne.

The numbers are significantly higher in Japan. "But they're rising here as well, which has a major affect on academics. Imagine a class where a third of the students aren't participating because they're dead tired."

Wiater recommends reducing a child's media consumption to promote sleep.

"An hour a day in front of the television or a computer can be enough to lead to sleeping disorders."

But timing is also a key factor.

"An exciting movie or video game right before bedtime delays tuning out. The contents of the show or the game are also important as they could lead to nightmares."

And exhaustion in children is no small matter. "Most children with sleeping disorders have some kind of mental disturbances, like fears, depression or hyperactivity."

"Four hours for men, five for women and six for idiots," was Napoleon Bonaparte's take on sleeping requirements. He is believed to have survived on even less sleep.

"There are no hard and fast rules. Not even a rule of thumb," says Mayer in response.

"We often get old people who want their eight hours of sleep. But their body doesn't need that much. Others complain that they only feel well rested after nine hours of sleep, which is also completely normal."

People who try to impress others by getting away with as little sleep as possible can soon find themselves in dangerous territory.

"Everyone needs his sleep. And we have no proof that people can train themselves to get by with less sleep."

Nonetheless, in the industrialized world, the amount of time spent sleeping has dropped by 1.5 hours. The average German sleeps about 7.1 hours a day.

To ensure that sleep is recuperative, researchers recommend a healthy diet and plenty of exercise. Fresh air and exercise contribute to healthy sleep. But it is best to take things easy before bedtime.

"Exercise and other stimuli sends out hormones that keep the body awake internally," warns Mayer. Though there is one exception to the rule - sex.

"We suspect there are positive benefits because the body gets stimuli, but then relaxes."