A small study in Sweden and the United States finds that using a cellphone just before bedtime interferes with sleep patterns.
Scientists at the Karolinska Institute and Uppsala University and Wayne State University in Detroit studied 35 men and 36 women. Thirty-eight of the volunteers said they had symptoms that they attributed to cellphone use, such as trouble concentrating and sleep problems. The other 33 volunteers reported no "mobile-related symptoms".
Half were exposed to 884 MHz wireless signals like that emitted by cellphones for three hours, while the others thought they were being exposed to it. The participants did not know which exposure they were receiving.
Those who were actually exposed to the radiation took longer to get into deep sleep. They also spent less time in the deepest part of sleep.
The participants took an average of about six minutes longer to reach the deep stage of sleep than when they had received the "sham" exposure. They also spent an average eight minutes less time in the deepest "stage 4" sleep.
Reports of headaches were greater during radio wave exposure than during sham exposure in the subjects who had previously not reported mobile-related symptoms. However, in those who were symptomatic, there was no difference in the reporting of headache between the two exposures.
Neither group was able to detect with accuracy whether they were being exposed to the true radio waves or to sham exposure.
The study is published by the Massachusetts Institute of Technology's Progress in Electromagnetics Research Symposium (PIERS). It was funded by the Mobile Manufacturers Forum, which called the results "inconclusive."
One of the study's researchers, Dr. Bengt Arnetz, says it appears that cellphones affect the areas of the brain responsible for activating and co-ordinating the stress system. It's also possible that radio waves disrupt production of the hormone melatonin, which controls the body's internal circadian rhythms.
Sleep expert Dr. Jeffrey Lipsitz says he finds the study's results disturbing.
"Aside from the sleep aspects, honestly, it's a little worrisome that you could measure any significant difference in people just because they've been exposed to radio waves that simulate cellphone use," he told Canada AM Monday.
"So you kind of wonder what else might be going on to the brain as a result of extended cellphone use, and what does that mean for all of us?... It certainly cries out for more research."
Lipsitz says the results of the study might have the greatest implications for teenages, who tend to use cellphones more in the evening and tend to talk for long periods of time.
"So if they're using cellphones for long hours in the evening and then going to sleep and their sleep is disturbed -- and they're the ones who probably need more sleep than the rest of us anyways and not getting it -- this may have implications with regard to health and development and functioning in school and so on. So there are some serious implications to this."
