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Using a mobile phone before going to bed could stop you getting a decent night's sleep, reports a new survey. According to research funded by the Mobile Manufacturers Forum, radiation from handsets can cause insomnia, headaches and confusion.

Over 70 men and women aged between 18 and 45 were exposed to varying levels of radiation, and their reactions were studied. Some were exposed to the equivalent radiation received when using a mobile phone, others were placed in the same conditions, but given only 'sham' exposure. Those exposed to radiation took longer to enter the first of the deeper stages of sleep, and spent less time in the deepest one, which interferes with the body's ability to refresh itself.

Researcher Professor Bengt Arnetz said: "The study strongly suggests that mobile phone use is associated with specific changes in the areas of the brain responsible for activating and coordinating the stress system."

The scientists also concluded that radiation may disrupt production of the hormone melatonin, which controls the body's internal rhythms.

Half of those surveyed believed themselves to be 'electrosensitive', reporting symptoms such as headaches from mobile phone use but they proved to be unable to tell if they had been exposed to the radiation in the test.

Alasdair Philips, director of Powerwatch, which researches the effects of electromagnetic fields on health, said: "The evidence is getting stronger that we should treat these things in a precautionary way. This research suggests that if you need to make a phone call in the evening it is much better to use a land line, and don't have your mobile by your bedside table."

Mike Dolan, executive director of the Mobile Operators Association, said the study was inconsistent with other research.

"It is really one small piece in a very large scientific jigsaw. It is a very small effect, one researcher likened it to less than the effect you would see from a cup of coffee," he said.

Last September a six-year study by the UK Mobile Telecommunications and Health Research Programme (MTHRP) concluded that mobile phone use posed no short-term risk to the brain, but researchers could not rule out the possibility that long-term use raising the risk of cancer.