Results of a new study suggest that using a mobile phone shortly before going to bed can lead to sleep disturbances and a number of other symptoms.
The study found that radiation from mobile/cell phone handsets can cause insomnia and interfere with stage-4 sleep (deep sleep) meaning users wake up feeling unrefreshed.
Other symptoms identified in connection with mobile phone use included headaches and confusion.
The study is a result of a collaborative research effort between Sweden's Karolinska Institute and Wayne State University in the US. It was funded by mobile phone manufacturers themselves through the Mobile Manufacturers Forum.
The study involved 35 men and 36 women aged between 18 and 45 who were split into an active group and a control group.
Participants in the active group were exposed to radiation equivalent to that received when using a mobile phone while those in the control group were given a "sham" exposure under identical conditions. Neither the participants or the scientists knew who was receiving the genuine radiation exposure.
When the results were analysed the scientists found a clear effect on the sleep quality of the participants who had been exposed to the radiation. Specifically, they took longer to enter the first of the deep sleep stages and spent less time in the deepest sleep stage.
Sleep is usually separated into four different stages, with stages 3 and 4 being defined as 'deep sleep'. It is in these stages where the body is able to recuperate with mental activity slowing greatly, blood being diverted away from the brain towards the muscles to restore physical energy, and immune function being boosted.
The scientists concluded: "The study indicates that during laboratory exposure to 884 MHz wireless signals components of sleep believed to be important for recovery from daily wear and tear are adversely affected."
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 findings seem to suggest that using mobile or cordless phones close to bed time may not be a good idea so it may be better to use a corded phone at this time if it is necessary to make a call.
Previous research on the subject has generally brought mixed results. Of two other studies published in 2007, one found that sleep onset was delayed after exposure to wireless phone radiation, while the other reported no significant effects on sleep or cognitive functions.
Source: Arnetz BB et al (2007) The Effects of 884 MHz GSM Wireless Communication Signals on Self-reported Symptom and Sleep (EEG)- An Experimental Provocation Study PIERS Online 3(7):1148-1150