To study possible effects of long-term electromagnetic field exposure to mobile phone handset-like signals (GSM and W-CDMA) on attention and working memory in 30 healthy male subjects (18-30 years old).
The subjects were tested on nine study days (separated by two week intervals) in which they were exposed to three exposure conditions (sham exposure, GSM and W-CDMA) in a randomly assigned and balanced order. All tests were presented twice (morning and afternoon) on each study day within a fixed timeframe.
| Exposure | Parameters |
|---|---|
|
Exposure 1:
900 MHz
Exposure duration:
3 days (à 7 h 15 minutes), separated by at least two week intervals
|
|
|
Exposure 2:
1,966 MHz
Exposure duration:
3 days (à 7 h 15 minutes), separated by 2-week intervals and not necessarily consecutive
|
9 study days (separated by 2-week intervals) with randomly assigned continuous exposure (sham exposure, GSM 900 and WCDMA/3G UMTS, 3 days each, not necessarily consecutive)
| Frequency | 900 MHz |
|---|---|
| Type | |
| Exposure duration | 3 days (à 7 h 15 minutes), separated by at least two week intervals |
| Additional info | GSM |
| Exposure source |
|
|---|---|
| Chamber | examination room with low background fields |
| Sham exposure | A sham exposure was conducted. |
| Additional info | antenna connected to a thin microwave RF coaxial cable; antenna designed like in cell phones |
| Exposure source |
|
|---|
Univariate comparison (t-test or Wilcoxon test) revealed significant changes when subjects were exposed to GSM exposure (higher number of correct reactions and shorter reaction time in the morning trial) compared to sham exposure, only in the vigilance test. In the W-CDMA exposure condition, one parameter in the vigilance (higher number of correct reactions) and one in the test on divided attention (slower reaction time in the morning session) were altered compared to sham exposure. Performance in the selective attention test and the n-back task was not affected by GSM or W-CDMA exposure. Time-of-day effects were evident for the tests on divided and selective attention, as well as for working memory.
After correction for multiple testing (Bonferroni inequality), only time-of-day effects remained significant in two tests, resulting in faster reactions in the afternoon trials.
The authors conclude, that the data do not provide any evidence of an electromagnetic field effect on human cognition, but they underline the necessity to control the paramter time-of-day.
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