Level 1: Likely reliable evidence
The effect of mobile-phone signals on headache was evaluated in a study of 71 “sensitive” participants aged 18-75 years who reported frequent headachelike symptoms occurring within 20 minutes of using a global system for communication (GSM) mobile phone. They were compared with 60 “controls” who had no such symptoms (BMJ. 2006;332:886-891; full text available online free of charge at http://bmj.bmjjournals.com, accessed November 7, 2006). Using a headband-mounted system, participants were exposed to three conditions in random order for 50 minutes each: 900-MHz GSM mobile-phone signal, nonpulsing carrier-wave signal, and a sham condition with no signal. A total of 60 “sensitive” and 60 “control” participants completed all three sessions. The primary outcome was bad sensations, including headaches; nausea; fatigue; dizziness; cutaneous itching, tingling, or stinging; sensations of warmth or burning on skin; and eye pain or dryness.
Subjects were asked to rate sensation severity from 0-10. Among “sensitive” subjects, the median symptom score increased from 0 to 7 over 50 minutes for GSM and sham groups and increased from 0 to 10 over 50 minutes in the continuous-wave group. Scores in all groups decreased to 3-4 by 80 minutes from start of exposure. Scores remained low on 0-100 scale for all groups, and there were no significant differences between groups. Similarly, there were no differences in rates of severe reactions (early cessation or study withdrawal) between groups. Among controls, all three groups had similar minimal effects with peak median score 1-2 at 50 minutes.