902 MHz mobile phone does not affect short term memory in humans

We studied the effects of an electromagnetic field (EMF) as emitted by a 902 MHz mobile phone on human short term memory. This study was a replication with methodological improvements to our previous study. The improvements included multi-centre testing and a double blind design. A total of 64 subjects (32 men) in two independent laboratories performed a short term memory task (n-back) which poses a varying memory load (0-3 items) on the subjects' memory. They performed the task twice, once each under EMF and sham exposure. Reaction times (RTs) and accuracy of the responses were recorded. The order of exposure and memory load conditions were counterbalanced across subjects and gender. There were no statistically significant differences in performance between the two laboratories. We could not replicate our previous results: the EMF had no effect on RTs or on the accuracy of the subjects' answers. The inability to replicate previous findings could have been caused by lack of actual EMF effects or the magnitude of effects being at the sensitivity threshold of the test used.     

Effects of electromagnetic field emitted by cellular phones on the EEG during an auditory memory task: a double blind replication study

The effects of electromagnetic fields (EMF) emitted by cellular phones on the event related desynchronization/synchronization (ERD/ERS) of the 4-6, 6-8, 8-10, and 10-12 Hz electroencephalogram (EEG) frequency bands were studied in 24 normal subjects performing an auditory memory task. This study was a systematic replication of our previous work. In the present double blind study, all subjects performed the memory task both with and without exposure to a digital 902 MHz field in a counterbalanced order. We were not able to replicate the findings from our earlier study. All eight of the significant changes in our earlier study were not significant in the present double blind replication. Also, the effect of EMF on the number of incorrect answers in the memory task was inconsistent. We previously reported no significant effect of EMF exposure on the number of incorrect answers in the memory task, but a significant increase in errors was observed in the present study. We conclude that EMF effects on the EEG and on the performance on memory tasks may be variable and not easily replicable for unknown reasons.     

Radio frequency electromagnetic field exposure in humans: Estimation of SAR distribution in the brain,effects on sleep and heart rate

In two previous studies we demonstrated that radiofrequency electromagnetic fields (RF EMF) similar to those emitted by digital radiotelephone handsets affect brain physiology of healthy young subjects exposed to RF EMF (900 MHz; spatial peak specific absorption rate [SAR] 1 W/kg) either during sleep or during the waking period preceding sleep. In the first experiment, subjects were exposed intermittently during an 8 h nighttime sleep episode and in the second experiment, unilaterally for 30 min prior to a 3 h daytime sleep episode. Here we report an extended analysis of the two studies as well as the detailed dosimetry of the brain areas, including the assessment of the exposure variability and uncertainties. The latter enabled a more in depth analysis and discussion of the findings. Compared to the control condition with sham exposure, spectral power of the non-rapid eye movement sleep electroencephalogram (EEG) was initially increased in the 9-14 Hz range in both experiments. No topographical differences with respect to the effect of RF EMF exposure were observed in the two experiments. Even unilateral exposure during waking induced a similar effect in both hemispheres. Exposure during sleep reduced waking after sleep onset and affected heart rate variability. Exposure prior to sleep reduced heart rate during waking and stage 1 sleep. The lack of asymmetries in the effects on sleep EEG, independent of bi- or unilateral exposure of the cortex, may indicate involvement of subcortical bilateral projections to the cortex in the generation of brain function changes, especially since the exposure of the thalamus was similar in both experiments (approx. 0.1 W/kg).     

Do people with idiopathic environmental intolerance attributed to electromagnetic fields display physiological effects when exposed to electromagnetic fields? A systematic review of provocation studies

Idiopathic environmental intolerance attributed to electromagnetic fields (IEI‐EMF) is a controversial illness in which people report symptoms that they believe are triggered by exposure to EMF. Double‐blind experiments have found no association between the presence of EMF and self‐reported outcomes in people with IEI‐EMF. No systematic review has assessed whether EMF exposure triggers physiological or cognitive changes in this group. Using a systematic literature search, we identified 29 single or double‐blind experiments in which participants with IEI‐EMF were exposed to different EMF levels and in which objectively measured outcomes were assessed. Five studies identified significant effects of exposure such as reduced heart rate and blood pressure, altered pupillary light reflex, reduced visual attention and perception, improved spatial memory, movement away from an EMF source during sleep and altered EEG during sleep. In most cases, these were isolated results that other studies failed to replicate. For the sleep EEG findings, the results reflected similar changes in the IEI‐EMF participants and a non‐IEI‐EMF control group. At present, there is no reliable evidence to suggest that people with IEI‐EMF experience unusual physiological reactions as a result of exposure to EMF. This supports suggestions that EMF is not the main cause of their ill health. Bioelectromagnetics. Bioelectromagnetics 32:593–609, 2011. © 2011 Wiley Periodicals, Inc.     

Electromagnetic treatment to old Alzheimer's mice reverses β-amyloid deposition, modifies cerebral blood flow, and provides selected cognitive benefit

Few studies have investigated physiologic and cognitive effects of "long-term" electromagnetic field (EMF) exposure in humans or animals. Our recent studies have provided initial insight into the long-term impact of adulthood EMF exposure (GSM, pulsed/modulated, 918 MHz, 0.25-1.05 W/kg) by showing 6+ months of daily EMF treatment protects against or reverses cognitive impairment in Alzheimer's transgenic (Tg) mice, while even having cognitive benefit to normal mice. Mechanistically, EMF-induced cognitive benefits involve suppression of brain β-amyloid (Aβ) aggregation/deposition in Tg mice and brain mitochondrial enhancement in both Tg and normal mice. The present study extends this work by showing that daily EMF treatment given to very old (21-27 month) Tg mice over a 2-month period reverses their very advanced brain Aβ aggregation/deposition. These very old Tg mice and their normal littermates together showed an increase in general memory function in the Y-maze task, although not in more complex tasks. Measurement of both body and brain temperature at intervals during the 2-month EMF treatment, as well as in a separate group of Tg mice during a 12-day treatment period, revealed no appreciable increases in brain temperature (and no/slight increases in body temperature) during EMF "ON" periods. Thus, the neuropathologic/cognitive benefits of EMF treatment occur without brain hyperthermia. Finally, regional cerebral blood flow in cerebral cortex was determined to be reduced in both Tg and normal mice after 2 months of EMF treatment, most probably through cerebrovascular constriction induced by freed/disaggregated Aβ (Tg mice) and slight body hyperthermia during "ON" periods. These results demonstrate that long-term EMF treatment can provide general cognitive benefit to very old Alzheimer's Tg mice and normal mice, as well as reversal of advanced Aβ neuropathology in Tg mice without brain heating. Results further underscore the potential for EMF treatment against AD.     

Human sleep under the influence of pulsed radiofrequency electromagnetic fields: A polysomnographic study using standardized conditions

To investigate the influence of radiofrequency electromagnetic fields (EMFs) of cellular phone GSM signals on human sleep electroencephalographic (EEG) pattern, all-night polysomnographies of 24 healthy male subjects were recorded, both with and without exposure to a circular polarized EMF (900 MHz, pulsed with a frequency of 217 Hz, pulse width 577 μs, power flux density 0.2 W/m². Suppression of rapid eye movement (REM) sleep as well as a sleep-inducing effect under field exposure did not reach statistical significance, so that previous results indicating alterations of these sleep parameters could not be replicated. Spectral power analysis also did not reveal any alterations of the EEG rhythms during EMF exposure. The failure to confirm our previous results might be due to dose-dependent effects of the EMF on the human sleep profile. Bioelectromagnetics 19:199–202, 1998. © 1998 Wiley-Liss, Inc.     

Effects of microwaves emitted by cellular phones on human slow brain potentials

The influence of electromagnetic fields (EMF) emitted by cellular phones on preparatory slow brain potentials (SP) was studied in two different experimental tasks: In the first, healthy male human subjects had to perform simple self-paced finger movements to elicit a Bereitschaftspotential; in the second, they performed a complex and cognitive demanding visual monitoring task (VMT). Both tasks were performed with and without EMF exposure in counterbalanced order. Whereas subjects' performance did not differ between the EMF exposure conditions, SP parameters were influenced by EMF in the VMT: EMF exposure effected a significant decrease of SPs at central and temporo-parieto-occipital brain regions, but not at the frontal one. In the simple finger movement task, EMF did not affect the Bereitschaftspotential. Bioelectromagnetics 19:384–387, 1998. © 1998 Wiley-Liss, Inc.     

Effects of RF‐EMF on the Human Resting‐State EEG—the Inconsistencies in the Consistency. Part 1: Non‐Exposure‐Related Limitations of Comparability Between Studies

The results of studies on possible effects of radiofrequency electromagnetic fields (RF‐EMFs) on human waking electroencephalography (EEG) have been quite heterogeneous. In the majority of studies, changes in the alpha‐frequency range in subjects who were exposed to different signals of mobile phone‐related EMF sources were observed, whereas other studies did not report any effects. In this review, possible reasons for these inconsistencies are presented and recommendations for future waking EEG studies are made. The physiological basis of underlying brain activity, and the technical requirements and framework conditions for conducting and analyzing the human resting‐state EEG are discussed. Peer‐reviewed articles on possible effects of EMF on waking EEG were evaluated with regard to non‐exposure‐related confounding factors. Recommendations derived from international guidelines on the analysis and reporting of findings are proposed to achieve comparability in future studies. In total, 22 peer‐reviewed studies on possible RF‐EMF effects on human resting‐state EEG were analyzed. EEG power in the alpha frequency range was reported to be increased in 10, decreased in four, and not affected in eight studies. All reviewed studies differ in several ways in terms of the methodologies applied, which might contribute to different results and conclusions about the impact of EMF on human resting‐state EEG. A discussion of various study protocols and different outcome parameters prevents a scientifically sound statement on the impact of RF‐EMF on human brain activity in resting‐state EEG. Further studies which apply comparable, standardized study protocols are recommended. Bioelectromagnetics. 2019;40:291–318. © 2019 The Authors. Bioelectromagnetics Published by Wiley Periodicals, Inc.     

Localizing Movement-Related Primary Sensorimotor Cortices with Multi-Band EEG Frequency Changes and Functional MRI

Electroencephalographic (EEG) oscillations in multiple frequency bands can be observed during functional activity of the cerebral cortex. An important question is whether activity of focal areas of cortex, such as during finger movements, is tracked by focal oscillatory EEG changes. Although a number of studies have compared EEG changes to functional MRI hemodynamic responses, we can find no previous research that relates the fMRI hemodynamic activity to localization of the multiple EEG frequency changes observed in motor tasks. In the present study, five participants performed similar thumb and finger movement tasks in parallel EEG and functional MRI studies. We examined changes in five frequency bands (from 5–120 Hz) and localized them using 256 dense-array EEG (dEEG) recordings and high-resolution individual head models. These localizations were compared with fMRI localizations in the same participants. Results showed that beta-band (14–30 Hz) desynchronizations (power decreases) were the most robust effects, appearing in all individuals, consistently localized to the hand region of the primary motor cortex, and consistently aligned with fMRI localizations.     

Perception of the electromagnetic field emitted by a mobile phone

Electromagnetic sensibility refers to the ability to perceive the electromagnetic field (EMF) without necessarily developing health symptoms attributed to EMF exposure. A large sample of young healthy adults (n = 84) performed two forced‐choice tasks on the perception of the GSM mobile phone EMF (902 MHz pulsed at 217 Hz), “Was the field on?” and “Did the field change?” (3 conditions × 100 trials for each task, n = 600 trials in total). A monetary prize was announced for good performance (correct response rate ≥75%, n = 600 trials). The performance was no better than expected by chance, and thus none of the participants won the prize. Two participants showed extraordinary performance in one of the task conditions (“Was the field on?”, n = 100 trials), with correct response rates of 97% (P = 1.28 × 10^?25) and 94% (P = 9.40 × 10^?22), but they failed to replicate the result in the retest of six blocks of the same condition 1 month later. Six participants had reported being able to perceive the mobile phone EMF in the preliminary inquiry, but they performed no better than the others. This study provides empirical evidence against the existence of electromagnetic sensibility to the mobile phone EMF, demonstrating the necessity for replication in EMF studies. Bioelectromagnetics 29:154–159, 2008. © 2007 Wiley‐Liss, Inc.     

Effect of a 902 MHz electromagnetic field emitted by mobile phones on human cognitive function: A replication study

Our study was a replication and extension with methodological improvements to a previous study on effects of the electromagnetic field (EMF) emitted by a 902 MHz mobile phone on human cognitive functioning. Improvements on the previous study included multicentre testing and a double blind design. A total of 64 subjects (32 men and 32 women) in two independent laboratories performed a battery of 9 cognitive tasks twice: while the EMF was on and while it was off. Reaction times (RTs) and accuracy were recorded. The order of exposure and tasks was counterbalanced across subjects and gender. There were no statistically significant differences in performance between genders or laboratories. Although the RTs and the accuracy of answers were very similar to those of our previous study, our previous results were not replicated. We concluded that EMF had no effect on RTs or on the accuracy of the subjects' answers. Further, our results indicate that our EMF had no immediate effect on human cognitive functioning or that such effects are so small that they are observed on behavior only occasionally.     

Changes in human EEG alpha activity following exposure to two different pulsed magnetic field sequences

The present study investigates the effects of a weak (+/-200 microT(pk)), pulsed, extremely low frequency magnetic field (ELF MF) upon the human electroencephalogram (EEG). We have previously determined that exposure to pulsed ELF MFs can affect the EEG, notably the alpha frequency (8-13 Hz) over the occipital-parietal region of the scalp. In the present study, subjects (n = 32) were exposed to two different pulsed MF sequences (1 and 2, used previously) that differed in presentation rate, in order to examine the effects upon the alpha frequency of the human EEG. Results suggest that compared to sham exposure, alpha activity was lowered over the occipital-parietal regions of the brain during exposure to Sequence 1, while alpha activity over the same regions was higher after Sequence 2 exposure. These effects occurred after approximately 5 min of pulsed MF exposure. The results also suggest that a previous exposure to the pulsed MF sequence determined subjects' responses in the present experiment. This study supports our previous observation of EEG changes after 5 min pulsed ELF MF exposure. The results of this study are also consistent with existing EEG experiments of ELF MF and mobile phone effects upon the brain.     

Identification of BDNF Sensitive Electrophysiological Markers of Synaptic Activity and Their Structural Correlates in Healthy Subjects Using a Genetic Approach Utilizing the Functional BDNF Val66Met Polymorphism

Increasing evidence suggests that synaptic dysfunction is a core pathophysiological hallmark of neurodegenerative disorders. Brain-derived neurotropic factor (BDNF) is key synaptogenic molecule and targeting synaptic repair through modulation of BDNF signalling has been suggested as a potential drug discovery strategy. The development of such “synaptogenic” therapies depend on the availability of BDNF sensitive markers of synaptic function that could be utilized as biomarkers for examining target engagement or drug efficacy in humans. Here we have utilized the BDNF Val66Met genetic polymorphism to examine the effect of the polymorphism and genetic load (i.e. Met allele load) on electrophysiological (EEG) markers of synaptic activity and their structural (MRI) correlates. Sixty healthy adults were prospectively recruited into the three genetic groups (Val/Val, Val/Met, Met/Met). Subjects also underwent fMRI, tDCS/TMS, and cognitive assessments as part of a larger study. Overall, some of the EEG markers of synaptic activity and brain structure measured with MRI were the most sensitive markers of the polymorphism. Met carriers showed decreased oscillatory activity and synchrony in the neural network subserving error-processing, as measured during a flanker task (ERN); and showed increased slow-wave activity during resting. There was no evidence for a Met load effect on the EEG measures and the polymorphism had no effects on MMN and P300. Met carriers also showed reduced grey matter volume in the anterior cingulate and in the (left) prefrontal cortex. Furthermore, anterior cingulate grey matter volume, and oscillatory EEG power during the flanker task predicted subsequent behavioural adaptation, indicating a BDNF dependent link between brain structure, function and behaviour associated with error processing and monitoring. These findings suggest that EEG markers such as ERN and resting EEG could be used as BDNF sensitive functional markers in early clinical development to examine target engagement or drug related efficacy of synaptic repair therapies in humans.     

Long-term effects of 60-Hz electric vs. magnetic fields on IL-1 and IL-2 activity in sheep

This study was designed to assess the effect of exposure to long-term extremely low-frequency electric and magnetic fields (ELF-EMF) from a 500 kV transmission line on IL-1 and IL-2 activity in sheep. The primary hypothesis was that the reduction in IL-1 activity observed in our two previous short-term studies (10 months) was due to EMF exposure from this transmission line. To repeat and expand these studies and to characterize the components of EMF responsible for the previously observed reduction in IL-1 activity, the current experiment examined not only the effect of exposure to electric and magnetic fields, but also the magnetic field component alone. In the current study, IL-2 was examined to characterize the effects of EMF exposure on an indicator of T cell responses. 45 Suffolk ewe lambs were randomized into three groups of 15 animals each. One group of animals was placed in the EMF pen, located directly beneath the transmission line. A second group was placed in the shielded MF (magnetic field only) pen, also directly beneath the transmission line. The third group of animals was placed in the control pen located several hundred meters away from the transmission line. During the 27 month exposure period, blood samples were taken from all animals monthly. When the data were analyzed collectively over time, no significant differences between the groups were found for IL-1 or IL-2 activity. In previous studies ewe lambs of 8-10 weeks of age were used as the study animals and significant differences in IL-1 activity were observed after exposure of these animals to EMF at mean magnetic fields of 3.5-3.8 microT (35-38 mG) and mean electric fields of 5.2-5.8 kV/m. At the start of the current study EMF levels were reduced as compared to previous studies. One interpretation of the current data is that magnetic field strength and age of the animals may be important variables in determining whether EMF exposure will affect IL-1 activity.     

Dependence of the non-thermal radiofrequency electromagnetic field bioeffects on the typological features of electroencephalogram in humans

In researches with participation of volunteers bioeffects of short-term non-thermal radiofrequency electromagnetic field (RF EMF) exposure were studied. The basic form of brain's reaction was the amplification of energy in a-range in electroencephalogram (EEG) spectra. Dependence of these changes, not only due to the changes of the exposure parameters, but also due to personal EEG typological features was shown. Moderate degree of the alpha frequencies domination in the background promoted development of reaction of a brain to the RF EMF exposure. To a lesser degree it was shown at hyperactivity of this range and, practically, was absent in the conditions of theta- or beta2-range domination in the EEG background with the open and closed eyes. The combination of RF EMF exposure and monotonous activity has authentically strengthened result, keeping the basic form of reaction (energy amplification in the alpha range of EEG spectrum) and dependence on EEG typological features.     

Pulsed and continuous wave mobile phone exposure over left versus right hemisphere: effects on human cognitive function

The possible effects of continuous wave (CW) and pulse modulated (PM) electromagnetic field (EMF) on human cognition was studied in 36 healthy male subjects. They performed cognitive tasks while exposed to CW, PM, and sham EMF. The subjects performed the same tasks twice during each session; once with left-sided and once with right-sided exposure. The EMF conditions were spread across three testing sessions, each session separated by 1 week. The exposed hemisphere, EMF condition, and test order were counterbalanced over all subjects. We employed a double-blind design: both the subject and the experimenter were unaware of the EMF condition. The EMF was created with a signal generator connected via amplifier to a dummy phone antenna, creating a power output distribution similar to the original commercial mobile phone. The EMF had either a continuous power output of 0.25 W (CW) or pulsed power output with a mean of 0.25 W. An additional control group of 16 healthy male volunteers performed the same tasks without any exposure equipment to see if mere presence of the equipment could have affected the subjects' performance. No effects were found between the different EMF conditions, separate hemisphere exposures, or between the control and experimental group. In conclusion, the current results indicate that normal mobile phones have no discernible effect on human cognitive function as measured by behavioral tests.     

Effects of mobile phone electromagnetic fields on an auditory order threshold task

The effect of acute exposure to radio frequency electromagnetic fields (RF EMF) generated by mobile phones on an auditory threshold task was investigated. 168 participants performed the task while exposed to RF EMF in one testing session (either global system for mobile communication (GSM) or unmodulated signals) while in a separate session participants were exposed to sham signals. Lateralization effects were tested by exposing participants either on the left side or on the right side of the head. No significant effect of exposure to RF EMF was detected, suggesting that acute exposure to RF EMFs does not affect performance in the order threshold task.     

Brain mechanisms of imagination in solving creative verbal tasks

The brain’s mechanisms of imagination were studied using electroencephalography (EEG) spectral analysis in student actors and student non-actors under three experimental conditions: when they generated coherent stories on the basis of art reproductions (STORY task); listed the details of art reproductions presented (DETAIL task); and performed simple arithmetic calculations while observing a neutral background (COUNT task). Statistical analysis showed that, in α₁ (7.5–10 Hz) and α₂ (10–12.5 Hz) frequency bands, in both groups, execution of the STORY task, in contrast to the DETAIL task, was accompanied by significantly higher spectral power (synchronization) in most of the cortical areas studied; while, the contrasts STORY-COUNT and DETAILS-COUNT, were associated with a decrease in the EEG’s power (desynchronization) in all of the areas studied. Topographic mapping of the EEG’s power showed that, in both groups, maximal differences between the STORY and DETAILS tasks were related to the central parietal area. Maximal differences between the STORY and COUNT tasks, as well as those between the DETAILS and COUNT tasks, were related mainly to the occipital areas. Based on these findings, we consider parietal areas to be stable elements of integrated brain mechanisms underlying verbal creativity in actors and nonactors. Comparing our data with previous studies, we suggest that the parietal areas are involved in the selective inhibition of visual information processing during the involvement of brain structures in the processes of imagination.     

Extremely low frequency electromagnetic fields as effectors of cellular responses in vitro: possible immune cell activation

There is presently an intense discussion if electromagnetic field (EMF) exposure has consequences for human health. This include exposure to structures and appliances that emit in the extremely low frequency (ELF) range of the electromagnetic spectrum, as well as emission coming from communication devices using the radiofrequency part of the spectrum. Biological effects of such exposures have been noted frequently, although the implication for specific health effects is not that clear. The basic interaction mechanism(s) between such fields and living matter is unknown. Numerous hypotheses have been suggested, although none is convincingly supported by experimental data. Various cellular components, processes, and systems can be affected by EMF exposure. Since it is unlikely that EMF can induce DNA damage directly, most studies have examined EMF effects on the cell membrane level, general and specific gene expression, and signal transduction pathways. In addition, a large number of studies have been performed regarding cell proliferation, cell cycle regulation, cell differentiation, metabolism, and various physiological characteristics of cells. Although 50/60 Hz EMF do not directly lead to genotoxic effects, it is possible that certain cellular processes altered by exposure to EMF indirectly affect the structure of DNA causing strand breaks and other chromosomal aberrations. The aim of this article is to present a hypothesis of a possible initial cellular event affected by exposure to ELF EMF, an event which is compatible with the multitude of effects observed after exposure. Based on an extensive literature review, we suggest that ELF EMF exposure is able to perform such activation by means of increasing levels of free radicals. Such a general activation is compatible with the diverse nature of observed effects. Free radicals are intermediates in natural processes like mitochondrial metabolism and are also a key feature of phagocytosis. Free radical release is inducible by ionizing radiation or phorbol ester treatment, both leading to genomic instability. EMF might be a stimulus to induce an "activated state" of the cell such as phagocytosis, which then enhances the release of free radicals, in turn leading to genotoxic events. We envisage that EMF exposure can cause both acute and chronic effects that are mediated by increased free radical levels: (1) Direct activation of, for example macrophages (or other cells) by short-term exposure to EMF leads to phagocytosis (or other cell specific responses) and consequently, free radical production. This pathway may be utilized to positively influence certain aspects of the immune response, and could be useful for specific therapeutic applications. (2) EMF-induced macrophage (cell) activation includes direct stimulation of free radical production. (3) An increase in the lifetime of free radicals by EMF leads to persistently elevated free radical concentrations. In general, reactions in which radicals are involved become more frequent, increasing the possibility of DNA damage. (4) Long-term EMF exposure leads to a chronically increased level of free radicals, subsequently causing an inhibition of the effects of the pineal gland hormone melatonin. Taken together, these EMF induced reactions could lead to a higher incidence of DNA damage and therefore, to an increased risk of tumour development. While the effects on melatonin and the extension of the lifetime of radicals can explain the link between EMF exposure and the incidence of for example leukaemia, the two additional mechanisms described here specifically for mouse macrophages, can explain the possible correlation between immune cell system stimulation and EMF exposure.     

Individual differences in the effects of mobile phone exposure on human sleep: rethinking the problem

Mobile phone exposure‐related effects on the human electroencephalogram (EEG) have been shown during both waking and sleep states, albeit with slight differences in the frequency affected. This discrepancy, combined with studies that failed to find effects, has led many to conclude that no consistent effects exist. We hypothesised that these differences might partly be due to individual variability in response, and that mobile phone emissions may in fact have large but differential effects on human brain activity. Twenty volunteers from our previous study underwent an adaptation night followed by two experimental nights in which they were randomly exposed to two conditions (Active and Sham), followed by a full‐night sleep episode. The EEG spectral power was increased in the sleep spindle frequency range in the first 30 min of non‐rapid eye movement (non‐REM) sleep following Active exposure. This increase was more prominent in the participants that showed an increase in the original study. These results confirm previous findings of mobile phone‐like emissions affecting the EEG during non‐REM sleep. Importantly, this low‐level effect was also shown to be sensitive to individual variability. Furthermore, this indicates that previous negative results are not strong evidence for a lack of an effect and, given the far‐reaching implications of mobile phone research, we may need to rethink the interpretation of results and the manner in which research is conducted in this field. Bioelectromagnetics 33:86–93, 2012. © 2011 Wiley Periodicals, Inc.