It's normal to be awake at night occasionally but the body must regularly change its status to ensure blood circulation."
There are myriad ways to solve the common problem of sleeplessness.
Difficulty in sleeping is not unusual when under stress. "Fears, worries or aggravation are negative emotions that lead to higher body activity," said Martin Muehlensiep of the sleep clinic at the University of Cologne.
Six to eight hours of sleep per night is the normal range in terms of the amount of sleep one should get. Hence it achieves nothing to go to bed at 10 p.m. and expect to sleep through until 8 a.m., said Kellner. "Also, the ability to perform is barely reduced after a nearly sleepless night."
When that happens, people often take the wrong course of action the next day. They often attempt to take it easy or even to take a nap, said Muehlensiep. "Then obviously they won't be tired the next evening and will lie awake in bed."
Limit your evening activities to a routine pattern, Muehlensiep recommends. First read, then put on pyjamas or a nightgown, and then brush your teeth, for example.
"Each of these activities will become a signal to the body that it's going to go to bed soon," Muehlensiep said. But what should one do when that doesn't help? Constantly looking at the clock puts pressure on the body.
"When that happens, it's better to get out of bed and do a simple activity," Kellner said. Put pictures into an album or iron, for example, until fatigue sets in.
People who can't sleep are often those who brood or worry a lot. Kellner advises people who have difficulty sleeping to exploit it and to let their thoughts take them on a journey. "Place yourself consciously in a pleasant situation: on a beach or in a meadow. This can replace the worries at hand."
People whose worries persistently spin around in their heads can try writing them down on a sheet of paper. "This doesn't make them go away, but keeps them for the next day." This often provides enough comfort to allow sleep to set in.
Food is best avoided two to three hours before going to bed. Coffee, nicotine and alcohol also impede falling asleep and therefore should not be consumed before bed.
"Alcohol can be good for falling asleep, but poor for staying asleep", said Muehlensiep. Bananas and milk products - the proven milk and honey method, for example - can help people sleep. They contain L- tryptophane and promote regular sleep patterns in the brain.
The bedroom also should be separated from all other rooms and dark.
"A desk, computer or television are reminders of stress and have no place in the bedroom," said Beate Horn, director of the sleep laboratory in Chemnitz. The optimal temperature is about 18 degrees centigrade.
Anyone experiencing back pain should think about replacing their mattress, if it's showing wear.