Downloaded from bmjopen.bmj.com
ABSTRACT Objectives: We performed a re-analysis of the data from Navarro et al (2003) in which health symptoms related to microwave exposure from mobile phone base stations (BSs) were explored, including data obtained in a retrospective inquiry about fear of exposure from BSs. Design: Cross-sectional study.
Setting: La Ñora (Murcia), Spain. Participants: Participants with known illness in 2003 were subsequently disregarded: 88 participants instead of 101 (in 2003) were analysed. Since weather circumstances can influence exposure, we restricted data to measurements made under similar weather conditions.
Outcomes and methods: A statistical method indifferent to the assumption of normality was employed: namely, binary logistic regression for modelling a binary response (eg, suffering fatigue (1) or not (0)), and so exposure was introduced as a predictor variable. This analysis was carried out on a regular basis and bootstrapping (95% percentile method) was used to provide more accurate CIs.
Results: The symptoms most related to exposure were lack of appetite (OR=1.58, 95% CI 1.23 to 2.03); lack of concentration (OR=1.54, 95% CI 1.25 to 1.89); irritability (OR=1.51, 95% CI 1.23 to 1.85); and trouble sleeping (OR=1.49, 95% CI 1.20 to 1.84). Changes in –2 log likelihood showed similar results. Concerns about the BSs were strongly related with trouble sleeping (OR =3.12, 95% CI 1.10 to 8.86).
The exposure variable remained statistically significant in the multivariate analysis. The bootstrapped values were similar to asymptotic CIs. Conclusions: This study confirms our preliminary results. We observed that the incidence of most of the symptoms was related to exposure levels— independently of the demographic variables and some possible risk factors. Concerns about adverse effects from exposure, despite being strongly related with sleep disturbances, do not influence the direct association between exposure and sleep.
The health risk due to exposure to radiofrequency electromagnetic fields (RF EMFs) continues to be discussed today.
The study that led to this debate was initiated after verification that the US embassy in Moscow was being subjected to such radiation from 1953 to May 1975.
Recently, a review of that episode reopened the debate about the potential harmfulness of RF EMFs.
The increasing number of base stations (BSs) on masts and buildings has increased public awareness. This issue has prompted scientific research to establish to what extent low-intensity EMFs may affect the health of humans and other organisms.
Furthermore, the term electromagnetic hypersensitivity has been recently introduced in discussions attributing symptoms to exposure to EMFs.
A review of this topic in 2010 found that 8 of the 10 studies evaluated through PubMed had reported increased prevalence of adverse neurobehavioral symptoms or cancer in populations living at distances <500 m from BSs.
None of the studies reported exposure above accepted international guidelines, suggesting that current guidelines may be inadequate in protecting health.
Thus, the need emerges to revaluate our pioneering work in this field in order to add new procedures and data.
Few articles have addressed the possible association between microwave sickness and microwave exposure from Global System for Mobile Communications (GSM) BSs since the publication of our first study.
Chronologically, Santini et al and Gadzicka et al reported differences in the distance dependent prevalence of symptoms such as headache, impaired concentration and Strengths and limitations of this study ▪ We used a robust statistical analysis with a highly homogeneous sample in a homogeneous environment. ▪ A participation bias cannot be ruled out.
The late query about concerns (as a possible confounder) may render the results less valid. ▪ We observed that the incidence of most of the symptoms was related to exposure levels. Gómez-Perretta C, Navarro EA, Segura J, et al. BMJ Open 2013;3:e003836. doi:10.1136/bmjopen-2013-003836 1 Open Access Research Downloaded from bmjopen.bmj.com on December 31, 2013 – Published by group.bmj.com irritability.
A later Austrian study showed a positive association between the measured electrical field (GSM 900/ 1800) in bedrooms and headaches, cold hands and feet and difficulties in concentration.
An Egyptian study showed a prevalence of neurological symptoms, such as headache, memory changes, dizziness, tremors, depressive symptoms and sleep disturbances among participants directly exposed to GSM signals from BSs. The symptoms reported by all the above cited authors belong to those attributed to the microwave syndrome.
However, one article using personal monitored data from GSM-UMTS frequency bands found no statistical association in adults. More recently, the same authors observed no association in children, contradictory results in children and adolescents, and concluded that the few observed significant associations were not causal but rather occurred by chance.
Blettner et al reported in phase 1 of their study more health problems closer to BSs, but in phase 2 they concluded that measured EMF emissions were not related to adverse health effects.
Other researchers focused their work on the possible existence of participants with sensitivity to GSM or UMTS signals according to psychological, cognitive or autonomic assessment. These researchers used short term exposure (only 30–50 min) under laboratory conditions and revealed a large disparity between participants.
Recently, a study measuring several biological stress markers found that RF EMF emitted by mobile phone BSs from 5.2 to 2126.8 μW/m2 increased cortisol and salivary α-amylase, while IgA concentration was not significantly modified. The Selbitz study in 2010 described a significant dose–response relationship in symptoms related with sleep, mood, joints, infections, skin condition, as well as neurological, cardiovascular, visual and auditory systems and the gastrointestinal tract.
The existence of short-term physiological effects of EMF on sleep quality was not evident in the work of Danker-Hopfe et al; however, it was stated that the presence of BSs per se (not the EMF) may have a negative impact on sleep quality.
A Polish study in 2012 did not show a correlation between electrical field strength and frequency of subjective symptoms; however, it showed a correlation between subjective symptoms and the distance to BSs.
A study carried out in Egypt revealed that exposure to EMF emitted either from mobile phones or BSs had significant effects on the pituitary–adrenal axis. More recently, work developed in Iran indicated that symptoms such as nausea, headache, dizziness, irritability, discomfort, nervousness, depression, sleep disturbance, memory loss and lowering of libido were statistically significant in people living near BSs (<300 m distances) compared with those living far from the BSs (>300 m).
In our cross-sectional analysis, of symptoms showed statistically significant higher scores in the group with the maximum exposure level. The symptoms are included in the microwave syndrome.
It also reported statistically significant correlation coefficients between the measured electrical field and of symptoms.
A review recently established several conditions for epidemiological studies to be eligible for introduction in general analysis: eligible studies must quantify exposure using objective measures (such as distance to the nearest BS, spot or personal exposure measurements in a specific frequency range); possible confounders must be considered and the selection of the study population must be clearly free of bias in terms of exposure and outcomes.
Accordingly, in this reanalysis of our previous study, possible confounders were included in addition to the specific RF EMF measurements made in 2001 (covering the specific range between 900 and 1800 MHz).
Therefore, we coanalysed the effects of other variables such as sociodemographic data and the use of electronic devices. Concern about being damaged by radiation from antennas was also analysed. The new statistical approach tested the possible influences of other variables, such as demographic data and the use of electronic devices.
Moreover, since some concerns have been raised about possible health consequences caused by the emitted microwaves, we analysed whether these symptoms might be related to fear of exposure.
As some participants refused to allow measurements in their homes, we analysed whether symptom status or subjective distance to the BS could be a bias of participation in the study.
Interestingly, this period was free of other sources of RF such as WIFI or UMTS or the massive use of mobile phones, enabling a specific study of GSM technology.
Finally, the suitability of the size of the sample was analysed.
METHODS Study design We chose a small urban area with mixed rural characteristics: low levels of environmental pollution (more agricultural than industrial); no major differences in socioeconomic characteristics throughout the region (excluding large cities); similar ethnicity (white Caucasian) and language (Spanish) and with mobile phone communication operative for at least 2 years.
La Ñora was chosen because it had the features of a small city, and was located near the capital (Murcia) in a rural environment without any particular health or environmental problems. Consequently, La Ñora was representative of small urban areas in eastern Spain with fewer than 20 000 inhabitants—such rural areas accounting for 19.8% of the population and 35.9% of the territory in Spain.
Two BS masts, each about 30 m height, were sited at different positions to provide GSM-900-1800 coverage.
The GSM 900 BS was positioned not before 1997 while the GSM 1800 BS was built in December 1999.
Data regarding the main demographic characteristics of the sample and their use of electronic devices was collected through a Spanish-language questionnaire.
All Gómez-Perretta C, Navarro EA, Segura J, et al. BMJ Open 2013;3:e003836. doi:10.1136/bmjopen-2013-003836 Open Access Downloaded from bmjopen.bmj.com on December 31, 2013 – Published by group.bmj.com of the participants were of the same ethnic origin, shared similar family income levels and general standard of living, and were born in La Ñora or nearby.
All the residents in the study were living in the village before the erection of both BSs. All of the residents were at home for more than 8 h a day for at least 6 days a week and normally slept at home. The core of the questionnaire was a symptom checklist for estimating the frequency of health-related symptoms attributed to microwave sickness. These symptoms were fatigue, irritability, headaches, nausea, loss of appetite, sleep disorders, depressive tendency, dizziness, concentration difficulties, memory loss, skin lesions, visual and hearing deficiencies, walking difficulties and cardiovascular problems.
The frequency was quantified as never suffer = 0, sometimes = 1, often = 2 and very often =3.
The percentage of residents who reported electrical transformers less than 10 m from their home was 21.6%, while 42% reported high-voltage power lines less than 100 m from home. Finally, 40% of residents reported a TV transmitter within a radius of around 4 km.
The questionnaire included a statement that its purpose was health research and that the data gathered would be confidential. Some 215 questionnaires were randomly distributed through 17 streets representing practically the entire village. The houses were selected using a street map of the village. In total, 150 questionnaires were collected with the remainder being uncollected because nobody was at home (31) or there was a refusal by the householder to complete the questionnaire (34).
During 2001, 101 RF EMF measurements in bedrooms were made. The other (49) residents who refused admittance for taking the measurements (16) were not at home for the scheduled measurement appointment (10) or had serious health problems (23). However, some changes are now being introduced in this reanalysis. Thirteen of the participants included in the original study have now been eliminated: 2 participants were eliminated (one regarding alcohol abuse and another regarding pregnancy) to increase the requirement on health criteria and 11 participants were eliminated to increase the homogeneity of the RF EMFs measurements because there was a change (it was raining) in the usual dry weather conditions when the respective broadband measurements were registered. The reanalysis of the dataset, which is the main focus of this paper, was finally performed with 88 participants (45 women and 43 men) instead of the 101 analysed in 2001. Concerns about microwave exposure Sixty-six of the 88 participants were reached by telephone in February 2012 and asked two questions: A. Were you worried about the masts (BSs) when they were erected? B. Did you believe their radiation (BSs) could damage your health? In all cases, those who were worried about the masts were concerned about health consequences. Twentyseven participants (40.9%) responded ‘no’ and 39 (59.1%) responded ‘yes’. Responses were analysed relative to age (analysis of variance (ANOVA) test), sex (λ statistic) and subjective distance to BS (Somers’ D statistic).
Demographic data and the percentage of users of personal computers and mobile phones were analysed. The
mean age was 42 and 17 years (SD±17. 61, interval 15–81). Women totalled 51.1% (mean age=45.08 years,
SD=17.98; interval=15–81) and 48.9% were men (mean age = 39.12 years, SD=16.88; interval=15–75). A total of
13.6% participants regularly used computers and 23.9%used mobile phones.
No differences related with age and use of mobile phones or computers were found between the sexes.
The univariate logistic regression indicated that age was inversely associated with irritability (OR=0.97, 95%
CI 0.95 to 0.99) and that the oldest had the greatest difficulties hearing (OR=1.03, 95% CI 1.01 to 1.06) and
walking (OR=1.04, 95% CI 1.01 to 1.07). However,gender clearly did not influence the outcome of any
dependent variable. Use of mobile phones was linked with lack of appetite and vertigo, while worry about the
radiation from BSs was associated with trouble sleeping(table 1). However, concern about radiation from BSs
was unrelated to age (ANOVA test), sex (λ statistic) or subjective distance to BS (Somers’ D statistic).
Most of the symptoms were related with GSM exposure especially fatigue, irritability, lack of appetite,
trouble sleeping, depression and lack of concentration.
Change in– log likelihood showed similar results(table 2). Figure 1 shows the distribution of EMF measurements
throughout the sample.ROC curves for each of the logistic regression models (GSM exposure vs each symptom) oscillated between0 .65 and 0.87 (table 3). Headaches (0.84), nausea (0.86), appetite (0.87) and vascular problems (0.85) showed the highest values, while memory (0.67), skin (0.67) and visual disturbances (0.65) showed the lowest
The Hosmer and Lemeshow test indicated that most analyses showed no significant p values. The exceptions
were fatigue (0.003), depression (0.003) and vertigo (0.03). In the majority of the cases, the models
predicted better specificity than sensitivity. Only in the case of headaches and sleep disorder, did sensitivity
prevail over specificity (table 3—classification table). In the extreme case, skin and vascular problems showed
null or minimum sensitivity and 100% specificity.
Nagelkerke pseudo R2 showed acceptable coefficients with the exception of the symptoms related with vertigo
and skin problems (table 3).Threshold cut-off values of GSM for sleep, attention, irritability and memory are also shown (table 3). The remaining cut-off values were not considered since sensitivity or specificity was reported at below 0.50%.
This new study partially confirms our preliminary results about microwave sickness resulting from exposure to emissions from GSM mobile phone BSs. Fatigue, irritability, lack of appetite, sleep troubles, depression and lack of concentration were especially related with GSM exposure.
These results were independent of the main sociodemographic variables, other EMF exposures and anxiety
about being irradiated. Nevertheless, we confirm that apprehension about modern technology could predict
some symptoms, especially those related with sleep problems.
Our results agree with those who claimed that by distorting perceptions of risk, disproportionate precaution might
paradoxically lead to illness that would not otherwise occur.
However, health changes related with GSM exposure seem to occur in a manner unrelated with those fears.
Finally, exposure was very low during the period and also very low in comparison with Spanish recommendations
and international guidelines. file:///E:/MEDICAL/2013_subjective_symptoms_related_to_gsm_radiation_from_mobile_phone_base_stations1.pdf