<%server.execute "isdev.asp"%> Does exposure to GSM 900 MHz mobile phone radiation affect short-term memory of elementary school students? Movvahedi M M, Tavakkoli-Golpayegani A, Mortazavi S, Haghani M, Razi Z, Shojaie-fard M B, Zare M, Mina E, Mansourabadi L, NJ, Safari A, Shokrpour N, Mortazavi S - J Pediatr Neurosci
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ORIGINAL ARTICLE
Year : 2014  |  Volume : 9  |  Issue : 2  |  Page : 121-124
 

Does exposure to GSM 900 MHz mobile phone radiation affect short-term memory of elementary school students?


1 Department of Medical Physics, Shiraz University of Medical Sciences, Shiraz, Iran
2 Standard Research Institute, Tehran, Iran
3 School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
4 Department of Radiology, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
5 The Center for Research on Protection against Ionizing and Nonionizing Radiation, School of Paramedical Sciences, Shiraz University of Medical Sciences, Shiraz, Iran
6 Department of Medical Physics; Departments of Medical Physics and Medical Engineering, Shiraz University of Medical Sciences, Shiraz, Iran

Date of Web Publication21-Aug-2014

Correspondence Address:
S. M. J. Mortazavi
Department of Medical Physics and Medical Engineering, The Center for Research on Protection against Ionizing and Nonionizing Radiation, Shiraz University of Medical Sciences, School of Medicine, Setad Square, Shiraz
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1817-1745.139300

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   Abstract 

Background: Now-a-days, children are exposed to mobile phone radiation at a very early age. We have previously shown that a large proportion of children in the city of Shiraz, Iran use mobile phones. Furthermore, we have indicated that the visual reaction time (VRT) of university students was significantly affected by a 10 min real/sham exposure to electromagnetic fields emitted by mobile phone. We found that these exposures decreased the reaction time which might lead to a better response to different hazards. We have also revealed that occupational exposures to radar radiations decreased the reaction time in radar workers. The purpose of this study was to investigate whether short-term exposure of elementary school students to radiofrequency (RF) radiation leads to changes in their reaction time and short-term memory. Materials and Methods: A total of 60 elementary school children ages ranging from 8 to 10 years studying at a public elementary school in Shiraz, Iran were enrolled in this study. Standardized computer-based tests of VRT and short-term memory (modified for children) were administered. The students were asked to perform some preliminary tests for orientation with the VRT test. After orientation, to reduce the random variation of measurements, each test was repeated ten times in both real and sham exposure phases. The time interval between the two subsequent sham and real exposure phases was 30 min. Results: The mean ± standard deviation reaction times after a 10 min talk period and after a 10 min sham exposure (switched off mobile) period were 249.0 ± 82.3 ms and 252.9 ± 68.2 ms (P = 0.629), respectively. On the other hand, the mean short-term memory scores after the talk and sham exposure periods were 1062.60 ± 305.39, and 1003.84 ± 339.68 (P = 0.030), respectively. Conclusion: To the best of our knowledge, this is the first study to show that short-term exposure of elementary school students to RF radiation leads to the better performance of their short-term memory.


Keywords: Children, cognitive responses, elementary school students, global system for mobile communication, mobile phone, radiofrequency, reaction time, short-term memory


How to cite this article:
Movvahedi M M, Tavakkoli-Golpayegani A, Mortazavi S, Haghani M, Razi Z, Shojaie-fard M B, Zare M, Mina E, Mansourabadi L, NJ, Safari A, Shokrpour N, Mortazavi S. Does exposure to GSM 900 MHz mobile phone radiation affect short-term memory of elementary school students?. J Pediatr Neurosci 2014;9:121-4

How to cite this URL:
Movvahedi M M, Tavakkoli-Golpayegani A, Mortazavi S, Haghani M, Razi Z, Shojaie-fard M B, Zare M, Mina E, Mansourabadi L, NJ, Safari A, Shokrpour N, Mortazavi S. Does exposure to GSM 900 MHz mobile phone radiation affect short-term memory of elementary school students?. J Pediatr Neurosci [serial online] 2014 [cited 2019 Jul 16];9:121-4. Available from: http://www.pediatricneurosciences.com/text.asp?2014/9/2/121/139300



   Introduction Top


Now-a-days, children are exposed to mobile phone radiation at a very early age. There is a rapidly growing concern about the possible health effects of radiofrequency (RF) radiation emitted by mobile phones on children's health. The potentially greater susceptibility of children's developing nervous systems, higher conductivity of their brain tissue, greater RF penetration due to their head size, and finally the fact that children have a longer lifetime exposure than adults are among the rational for these concerns. [1] Moreover, it has been reported that the specific absorption rate (SAR) of RF radiation in the children's brain is higher than that of the adults. Differences in the size, shape, water content and tissue distribution of the brain in children are believed to be responsible for the higher SAR and vulnerability of children. On the other hand, the issue of children carrying mobile phones in schools and using these communicational devices during instructional time is another important concern. In the Islamic Republic of Iran, the use of mobile phone in schools is banned. However, similar to other countries in some schools the policies regarding mobile phone use are being somehow relaxed. [2] In a report published in 2011, we have shown that a large proportion of children in the city of Shiraz, Iran use mobile phones. We also indicated a significant increase in some self-reported symptoms among children who use mobile phones. [2]

Reaction time plays a critical role in performing activities necessary to cope better with life's threats and/or avoid hazards. Reaction time widely varies from one individual to another, and increased reaction time may lead to fatal accidents. We and other investigators have previously studied the effects of exposure to electromagnetic fields (EMF) on reaction time. [3],[4],[5],[6],[7] Previously, we have indicated that the visual reaction time (VRT) of university students was significantly affected by a 10 min real/sham exposure to EMF emitted by mobile phone. [7] We found that these exposures caused decreased reaction time, which might lead to a better response to different hazards. We have previously also shown that occupational exposures to radar radiations decreased reaction time in radar workers. [8] Over the past years, our laboratory has focused on studying the health effects of exposure of laboratory animals and humans to some common and/or occupational sources of EMF such as mobile phones [7],[8],[9],[10],[11],[12],[13],[14] and their base stations, [15] mobile phone jammers, [16] laptop computers, [17] radars, [8] dentistry cavitrons [18] and MRI. [13],[19] The purpose of this study was to investigate whether short-term exposure of elementary school students to RF radiation leads to changes in their reaction time and short-term memory.


   Materials and Methods Top


In this study, sixty male elementary school children, in the age group of 7-10-year-old at a boys' public elementary school in Shiraz, Iran were the subjects of the study. The purpose of the study was explained to the students and teachers, and a letter explaining the goal of the study and consent form were sent to the children's parents. The study was approved by the Ethics Committee of the Shiraz University of Medical Sciences. Left-handed students were excluded from the study. Computer-assisted-tests of VRT and short-term memory (modified for children) were administered. Reaction time is usually defined as the time interval between exposure to a stimulus and detection of a response; in the present study, it was the amount of time it took an individual to physically respond to the visual stimulus on the display of a laptop computer. The students were asked to perform some preliminary tests for orientation with the VRT test. After orientation, to reduce random variation of measurements, each test was repeated ten times in both real and sham exposure phases. The students' VRT was recorded with a simple blind computer assisted-test, before and after a 10 min real/sham exposure to EMF of mobile phone. The reason for choosing 10 min intervals for either real exposures or sham exposures was the point that based on our previous studies, [2] only about 16% of the male and 11% of the female students had daily call time longer than 10 min. In this light, a 10 min exposure could represent a common condition. Participants were asked to sit in an armchair in front of an ergonomic liquid-crystal display monitor. The time interval between the two subsequent sham and real exposure phases was 30 min. A GSM Huawei G5520 mobile phone (Huawei Technologies Co. Ltd., China) was used for exposure to microwaves. According to manufacturer's specifications, the highest SAR value under the ICNIRP guidelines for using this device at the ear was 1.45 W/kg. The phone was in a normal talk mode but as the loudspeaker was disconnected, it did not produce any sound. The students were informed that during the experiment they would be exposed to EMF emitted by mobile phone, but they were not aware of the order of real/sham exposures. The order of the exposures (sham-real or real-sham) was chosen at random for each participant.


   Results Top


The participants' mean (± standard deviation [SD]) age was 8.81 ± 0.82 (ranged, 7-10) years. The majority of them were between 8 and 9 years of age (74.58%). Among the participants, 10.2% were 1 st year students, while 13.6%, 61.0% and 15.2% were 2 nd , 3 rd and 4 th year students. The mean (± SD) reaction time after a 10 min talk period and after a 10 min sham exposure (switched off mobile) period were 249.0 ± 82.3 ms and 252.9 ± 68.2 ms (P = 0.629), respectively [Figure 1]. On the other hand, the mean short-term memory scores after the talk and sham exposure periods were 1062.60 ± 305.39 and 1003.84 ± 339.68 (P = 0.030), respectively [Figure 2].
Figure 1: The mean (± standard deviation) reaction time after a 10 min talk period and after a 10 min sham exposure (switched off mobile) period

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Figure 2: The mean short-term memory scores after the talk and sham exposure periods

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   Discussion Top


Results obtained in this study showed that a 10 min talk period could not alter the reaction time in elementary school students, while exposures are extending over a short period of time significantly increased the short-term memory scores. To the best of our knowledge, this is the first study to show that short-term exposure of elementary school students to RF radiation leads to the better performance of their short-term memory. These findings, along with our previous reports, [7],[8] rule out the widespread assumption that mobile-emitted-radiations increase the reaction time.

Mortazavi et al. have previously reported some beneficial cognitive effects after human short-term exposure to cell phone radiation. In a report published in 2011, Mortazavi et al. showed that the VRT of university students was significantly affected by a 10 min exposure to EMF emitted by mobile phone. [7] They found that these exposures caused decreased reaction time which might lead to a better response to different hazards. They also revealed that occupational exposure to radar radiations decreased the reaction time in radar workers. [8] Increased brain glucose consumption after exposure to RF radiation, as confirmed by PET studies, may be a potential mechanism in this phenomenon.

Our findings are in line with those published by Vecchio et al. in 2012. In their study, subjects underwent two electroencephalographic sessions separated by 1-week. In both sessions, participants conducted a visual go/no-go task before a 45 min real exposure phase to mobile phone GSM EMF or after a sham exposure phase (no EMF). Results of this study showed less power decrease of widely distributed high-frequency alpha rhythms and faster reaction time while no effect was detected in the sham exposure phase. Vecchio et al. concluded that both the peak amplitude of alpha event-related desynchronization and the reaction time are modulated by the effect of the exposure to EMF of GSM mobile phone on the cortical activity. Furthermore, cognitive beneficial effects of long-term exposure to high-frequency EMF have been indicated by some epidemiologic studies. Using a word interference test, Arns et al. showed that long-term heavy cell phone use resulted in better performance of normal subjects. [20] Moreover, Schüz et al. in 2009 reported that long-term cell phone users B (subscribers of 10 years or more) had a 30-40% decreased risk of hospitalization due to Alzheimer's disease and vascular dementia. [21]

On the other hand, our results contradict those of the previous studies such as that conducted by a group of Australian scientists who investigated the reaction time and accuracy rate data during the auditory oddball task. Their study showed an increased reaction time after the exposure compared to sham-exposure intervals. [22] Our results are also in contrast with those reported in 2006, indicating that exposure to pulsed EMFs produced by mobile phone has no short-term effects on human visuomotor choice reaction time and movement time. [23] In this double-blind study, that was claimed by the authors to be the first study to assess human visuomotor behavior after a short-term exposure to mobile phone-generated radiation, it was shown that a 30 min exposure could not change the reaction time. Our findings are also in contrast with those of a report that was performed on the effect of exposure to mobile phone radiation on the nervous system activity. This study showed that acute exposure to mobile phone radiation could not induce any change in studied indices of brain activity. [24] As each brain hemisphere is dominant for some of our behaviors, in future studies appropriate tests can be performed separately for right and left brain functions to obtain more powerful results. On the other hand, although the SAR value reported in this study (1.45 W/kg) was a manufacturer's reported highest SAR value under the ICNIRP guidelines for using this phone, in future studies energy absorbed by a unit of mass of exposed tissue over a given time of a person who uses a mobile phone can be measured.


   Conclusion Top


To the best of our knowledge, this is the first study to show that short-term exposure of elementary school students to RF radiation leads to the better performance of their short-term memory. This memory enhancing intervention may open new horizons in the treatment of some cognitive impairment problems.


   Acknowledgments Top


This study was supported by the Center for Research on Protection against ionizing and nonionizing radiation, Shiraz University of Medical Sciences (SUMS), Shiraz, Iran.

 
   References Top

1.Kheifets L, Repacholi M, Saunders R, van Deventer E. The sensitivity of children to electromagnetic fields. Pediatrics 2005;116:e303-13.  Back to cited text no. 1
    
2.Mortazavi SM, Atefi M, Kholghi F. The pattern of mobile phone use and prevalence of self-reported symptoms in elementary and junior high school students in Shiraz, Iran. Iran J Med Sci 2011;36:96-103.  Back to cited text no. 2
    
3.Vecchio F, Buffo P, Sergio S, Iacoviello D, Rossini PM, Babiloni C. Mobile phone emission modulates event-related desynchronization of α rhythms and cognitive-motor performance in healthy humans. Clin Neurophysiol 2012;123:121-8.  Back to cited text no. 3
    
4.Leung S, Croft RJ, McKenzie RJ, Iskra S, Silber B, Cooper NR, et al. Effects of 2G and 3G mobile phones on performance and electrophysiology in adolescents, young adults and older adults. Clin Neurophysiol 2011;122:2203-16.  Back to cited text no. 4
    
5.Valentini E, Ferrara M, Presaghi F, De Gennaro L, Curcio G. Systematic review and meta-analysis of psychomotor effects of mobile phone electromagnetic fields. Occup Environ Med 2010;67:708-16.  Back to cited text no. 5
    
6.Kleinlogel H, Dierks T, Koenig T, Lehmann H, Minder A, Berz R. Effects of weak mobile phone - Electromagnetic fields (GSM, UMTS) on event related potentials and cognitive functions. Bioelectromagnetics 2008;29:488-97.  Back to cited text no. 6
    
7.Mortazavi SM, Rouintan MS, Taeb S, Dehghan N, Ghaffarpanah AA, Sadeghi Z, et al. Human short-term exposure to electromagnetic fields emitted by mobile phones decreases computer-assisted visual reaction time. Acta Neurol Belg 2012;112:171-5.  Back to cited text no. 7
    
8.Mortazavi SM, Taeb S, Dehghan N. Alterations of visual reaction time and short term memory in military radar personnel. Iran J Public Health 2013;42:428-35.  Back to cited text no. 8
    
9.Mortazavi SM, Motamedifar M, Namdari G, Taheri M, Mortazavi AR, Shokrpour N. Non-linear adaptive phenomena which decrease the risk of infection after pre-exposure to radiofrequency radiation. Dose Response 2014;12:233-45.  Back to cited text no. 9
    
10.Mortazavi S, Mosleh-Shirazi M, Tavassoli A, Taheri M, Mehdizadeh A, Namazi S, et al. Increased Radioresistance to Lethal Doses of Gamma Rays in Mice and Rats after Exposure to Microwave Radiation Emitted by a GSM Mobile Phone Simulator. Dose Response 2013;11:281-92.  Back to cited text no. 10
    
11.Mortazavi S, Mosleh-Shirazi M, Tavassoli A, Taheri M, Bagheri Z, Ghalandari R, et al. A comparative study on the increased radioresistance to lethal doses of gamma rays after exposure to microwave radiation and oral intake of flaxseed oil. Iran J Radiat Res 2011;9:9-14.  Back to cited text no. 11
    
12.Mortavazi S, Habib A, Ganj-Karami A, Samimi-Doost R, Pour-Abedi A, Babaie A. Alterations in TSH and thyroid hormones following mobile phone use. Oman Med J 2009;24:274-8.  Back to cited text no. 12
    
13.Mortazavi SM, Daiee E, Yazdi A, Khiabani K, Kavousi A, Vazirinejad R, et al. Mercury release from dental amalgam restorations after magnetic resonance imaging and following mobile phone use. Pak J Biol Sci 2008;11:1142-6.  Back to cited text no. 13
    
14.Mortazavi SM, Ahmadi J, Shariati M. Prevalence of subjective poor health symptoms associated with exposure to electromagnetic fields among university students. Bioelectromagnetics 2007;28:326-30.  Back to cited text no. 14
    
15.Mortazavi SM. Safety issue of mobile phone base stations J Biomed Phys Eng 2013;3:1-2.  Back to cited text no. 15
    
16.Mortazavi S, Parsanezhad M, Kazempour M, Ghahramani P, Mortazavi A, Davari M. Male reproductive health under threat: Short term exposure to radiofrequency radiations emitted by common mobile jammers. J Hum Reprod Sci 2013;6:124-8.  Back to cited text no. 16
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17.Mortazavi SM, Tavasoli AR, Ranjbari F, Moamaei P. Effects of laptop computers′ electromagnetic field on sperm quality. J Reprod Infertil 2011;11:251-8.  Back to cited text no. 17
    
18.Mortazavi SM, Vazife-Doost S, Yaghooti M, Mehdizadeh S, Rajaie-Far A. Occupational exposure of dentists to electromagnetic fields produced by magnetostrictive cavitrons alters the serum cortisol level. J Nat Sci Biol Med 2012;3:60-4.  Back to cited text no. 18
    
19.Mortazavi SM, Neghab M, Anoosheh SM, Bahaeddini N, Mortazavi G, Neghab P, Rajaeifard A, et al. High-field MRI and mercury release from dental amalgam fillings. Int J Occup Environ Med 2014;5:101-5.  Back to cited text no. 19
    
20.Arns M, Van Luijtelaar G, Sumich A, Hamilton R, Gordon E. Electroencephalographic, personality, and executive function measures associated with frequent mobile phone use. Int J Neurosci 2007;117:1341-60.  Back to cited text no. 20
    
21.Schüz J, Waldemar G, Olsen JH, Johansen C. Risks for central nervous system diseases among mobile phone subscribers: A Danish retrospective cohort study. PLoS One 2009;4:e4389.  Back to cited text no. 21
    
22.Hamblin DL, Wood AW, Croft RJ, Stough C. Examining the effects of electromagnetic fields emitted by GSM mobile phones on human event-related potentials and performance during an auditory task. Clin Neurophysiol 2004;115:171-8.  Back to cited text no. 22
    
23.Terao Y, Okano T, Furubayashi T, Ugawa Y. Effects of thirty-minute mobile phone use on visuo-motor reaction time. Clin Neurophysiol 2006;117:2504-11.  Back to cited text no. 23
    
24.Hamblin DL, Croft RJ, Wood AW, Stough C, Spong J. The sensitivity of human event-related potentials and reaction time to mobile phone emitted electromagnetic fields. Bioelectromagnetics 2006;27:265-73.  Back to cited text no. 24
    


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