Source of funding and results of studies of health effects of Mobile phone use: systematic review of experimental studies.OBJECTIVES: There is concern regarding the possible health effects of cellular telephone use. We examined whether the source of funding of studies of the effects of low-level radiofrequency radiation is associated with the results of studies. We conducted a systematic review of studies of controlled exposure to radiofrequency radiation with health-related outcomes (electroencephalogram electroencephalogram /elec·tro·en·ceph·a·lo·gram/ (EEG) (-en-sef´ah-lo-gram?) a recording of the potentials on the skull generated by currents emanating spontaneously from nerve cells in the brain, with fluctuations in potential seen as , cognitive or cardiovascular function, hormone levels, symptoms, and subjective well-being). DATA SOURCES: We searched EMBASE, Medline, and a specialist database in February 2005 and scrutinized reference lists from relevant publications. DATA EXTRACTION Data extraction is the act or process of retrieving (binary) data out of (usually unstructured or badly structured) data sources for further data processing or data storage (data migration). : Data on the source of funding, study design, methodologic quality, and other study characteristics were extracted. The primary outcome was the reporting of at least one statistically significant association between the exposure and a health-related outcome. Data were analyzed an·a·lyze tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es 1. To examine methodically by separating into parts and studying their interrelations. 2. Chemistry To make a chemical analysis of. 3. using logistic regression In statistics, logistic regression is a regression model for binomially distributed response/dependent variables. It is useful for modeling the probability of an event occurring as a function of other factors. models. DATA SYNTHESIS data synthesis Meta-analysis, see there : Of 59 studies, 12 (20%) were funded exclusively by the telecommunications industry, 11 (19%) were funded by public agencies or charities, 14 (24%) had mixed funding (including industry), and in 22 (37%) the source of funding was not reported. Studies funded exclusively by industry reported the largest number of outcomes, but were least likely to report a statistically significant result: The odds ratio was 0.11 (95% confidence interval confidence interval, n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. , 0.02-0.78), compared with studies funded by public agencies or charities. This finding was not materially altered in analyses adjusted for the number of outcomes reported, study quality, and other factors. CONCLUSIONS: The interpretation of results from studies of health effects of radiofrequency radiation should take sponsorship into account. KEY WORDS: electromagnetic fields electromagnetic field Property of space caused by the motion of an electric charge. A stationary charge produces an electric field in the surrounding space. If the charge is moving, a magnetic field is also produced. A changing magnetic field also produces an electric field. , financial conflicts of interest, human laboratory studies, mobile phones. Environ Health Perspect 115:1-4 (2007). doi: 10.1289/ehp.9149 available via http://dx.doi.org/[Online 15 September 2006] ********** The use of mobile telephones has increased rapidly in recent years. The emission of low-level radiofrequency electromagnetic fields leading to the absorption of radiation by the brain in users of handheld mobile phones has raised concerns regarding potential effects on health (Rothman 2000). However, the studies examining this issue have produced conflicting results, and there is ongoing debate on this issue (Ahlbom et al. 2004; Feychting et al. 2005). Many of the relevant studies have been funded by the telecommunications industry, and thus may have resulted in conflicts of interest (Thompson 1993). Recent systematic reviews of the influence of financial interests in medical research concluded that there is a strong association between industry sponsorship and pro-industry conclusions (Bekelman et al. 2003; Yaphe et al. 2001). This association has not been examined in the context of the studies of potential adverse effects of mobile phone use. We performed a systematic review and analysis of the literature to examine whether industry involvement is associated with the results and methodologic quality of studies. Methods We searched EMBASE (http://www.embase.com) and Medline (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed) in February 2005. Key and free text words included "cell(ular)," "mobile," "(tele ("long distance") Operations performed remotely or by telephone. The "tele" prefix is used to designate many technologies such as telecommunications and teleconferencing. )phone(s)" in connection with "attention," "auditory auditory /au·di·to·ry/ (aw´di-tor?e) 1. aural or otic; pertaining to the ear. 2. pertaining to hearing. au·di·to·ry adj. ," "bioelectric bi·o·e·lec·tric also bi·o·e·lec·tri·cal adj. 1. Of or having to do with the electric current generated by living tissue. 2. Of or relating to the effects of electricity on living tissue. ," "brain physiology physiology (fĭzēŏl`əjē), study of the normal functioning of animals and plants during life and of the activities by which life is maintained and transmitted. It is based fundamentally on the activities of protoplasm. ," "cardiovascular," "cerebral," "circulatory circulatory /cir·cu·la·to·ry/ (ser´ku-lah-tor?e) 1. pertaining to circulation, particularly that of the blood. 2. containing blood. cir·cu·la·to·ry n. 1. ," "cognitive," "EEG EEG: see electroencephalography. ," "health complaint(s)," "hearing," "heart rate," "hormone(s)," "learning," "melatonin melatonin: see pineal gland. melatonin Hormone secreted by the pineal gland of most vertebrates. It appears to be important in regulating sleeping cycles; more is produced at night, and test subjects injected with it become sleepy. ," "memory," "neural," "neurological neurological, neurologic pertaining to or emanating from the nervous system or from neurology. neurological assessment evaluation of the health status of a patient with a nervous system disorder or dysfunction. ," "nervous system," "reaction," "visual," "symptom(s)," or "well-being." The search was complemented with references from a specialist database (ELMAR 2005) and by scrutinizing reference lists from the relevant publications. Articles published in English, German, or French were considered. We included original articles that reported studies of the effect of controlled exposure with radiofrequency radiation on health-related outcomes ["human laboratory studies" in World Health Organization (WHO) terminology (Repacholi 1998)]. Health-related outcomes included electroencephalogram (EEG) recordings, assessments of cognitive or cardiovascular function, hormone levels, and subjective well-being and symptoms. We excluded studies of the risk of using mobile phones when driving a motor vehicle or operating machinery as well as studies on electromagnetic field (EMF emf: see electromotive force. (1) (ElectroMagnetic Field) See electromagnetic radiation. (2) (Enhanced MetaFile) See Windows metafile. ) incompatibilities (e.g., pacemakers Pacemakers Definition A pacemaker is a surgically-implanted electronic device that regulates a slow or erratic heartbeat. Purpose Pacemakers are implanted to regulate irregular contractions of the heart (arrhythmia). or hearing aids Hearing Aids Definition A hearing aid is a device that can amplify sound waves in order to help a deaf or hard-of-hearing person hear sounds more clearly. ). Three of us (A.H., K.H., M.R.) independently extracted data on the source of funding (industry, public or charity, mixed, not reported) and potential confounding confounding when the effects of two, or more, processes on results cannot be separated, the results are said to be confounded, a cause of bias in disease studies. confounding factor factors, including study design (crossover Crossover The point on a stock chart when a security and an indicator intersect. Crossovers are used by technical analysts to aid in forecasting the future movements in the price of a stock. In most technical analysis models, a crossover is a signal to either buy or sell. , parallel, other), exposure (frequency band, duration, field intensity, and location of antenna), and methodologic and reporting quality. Four dimensions of quality were assessed (Joni et al. 2001; Repacholi 1998): a) randomized ran·dom·ize tr.v. ran·dom·ized, ran·dom·iz·ing, ran·dom·iz·es To make random in arrangement, especially in order to control the variables in an experiment. , concealed allocation of study participants in parallel or crossover trials; b) blinding of participants and investigators to allocation group An AG or allocation group is a subvolume in a file system which maintains its own track of free blocks and file data (and its own journal, in the case of XFS). This makes simultaneous file operations possible; only one write can happen to an AG at any time, but multiple ; c) reporting of the specific absorption rate Specific Absorption Rate (SAR) is a measure of the rate at which radio frequency (RF) energy is absorbed by the body when exposed to radio-frequency electromagnetic field. The most common use is in relation to cellular telephones. (SAR (Segmentation And Reassembly) The protocol that converts data to cells for transmission over an ATM network. It is the lower part of the ATM Adaption Layer (AAL), which is responsible for the entire operation. See AAL. SAR - segmentation and reassembly ; watts per kilogram kilogram, abbr. kg, fundamental unit of mass in the metric system, defined as the mass of the International Prototype Kilogram, a platinum-iridium cylinder kept at Sèvres, France, near Paris. tissue) from direct measurement using a phantom head or three-dimensional dosimetric calculations ("appropriate exposure setting"); d) appropriate statistical analysis. For each item, studies were classified as adequate or inadequate/unclear. The primary outcome was the reporting of at least one statistically significant (p < 0.05) association between radiofrequency exposure and a health-related outcome. The message in the title was also assessed. We distinguished among neutral titles [e.g., "Human brain activity during exposure to radiofrequency fields emitted by cellular phones" (Hietanen et al. 2000)], titles indicating an effect of radiation [e.g., "Exposure to pulsed high-frequency electromagnetic field during waking affects human sleep EEG" (Huber et al. 2000)], and titles stating that no effect was shown [e.g., "No effect on cognitive function cognitive function Neurology Any mental process that involves symbolic operations–eg, perception, memory, creation of imagery, and thinking; CFs encompasses awareness and capacity for judgment from daily mobile phone use" (Besset et al. 2005)]. Finally, authors' declaration of conflicts of interest (present, absent) and affiliations (industry, other) were recorded. Differences in data extracted by A.H., K.H., and M.R. were resolved in the group, with the senior epidemiologist epidemiologist an expert in epidemiology. (M.R.) acting as the arbiter. In addition, two of us (K.H.M., M.E.), who were kept blind to funding source, authors, and institutions, repeated extraction of data from abstracts and assessments of titles. Differences in data extracted by K.H.M. and M.E. were resolved with the senior epidemiologist (M.E.) acting as the arbiter. Based on the abstracts, we assessed whether authors interpreted their study results as showing an effect of low-level radiofrequency radiation, as showing no effect, or as indicating an unclear finding. We used logistic regression models to assess whether the source of funding was associated with the reporting of at least one significant effect in the article (including the abstract). We examined the influence of potential confounders, such as the total number of outcomes that were reported in the article, the type of study (crossover, parallel, other), the four dimensions of study quality (adequate or not adequate/unclear), exposure conditions (position of the antenna next to the ear compared with other locations; use of the 900-MHz band compared with other bands; duration of exposure in minutes), as well as the type of outcome (e.g., cognitive function tests: yes vs. no). Variables were entered one at a time and, given the limited number of studies, models were adjusted for one variable only. Results are reported as odds ratios (ORs) with 95% confidence intervals (CIs). All analyses were carried out in Stata (version 8.2; StataCorp., College Station, TX, USA). Results We identified 222 potentially relevant publications and excluded 163 studies that did not meet inclusion criteria
Inclusion criteria are a set of conditions that must be met in order to participate in a clinical trial. (Figure 1). We excluded one study that had been funded by a company producing "shielding" devices that reduce EMF exposure (Croft CROFT, obsolete. A little close adjoining to a dwelling-house, and enclosed for pasture or arable, or any particular use. Jacob's Law Dict. et al. 2002). A total of 59 studies were included: 12 (20%) were exclusively funded by the telecommunications industry, 11 (19%) were funded by public agencies or charities, 14 (24%) had mixed funding (including industry and industry-independent sources), and in 22 (37%) studies the source of funding was not reported. None of 31 journals published a statement on possible conflicts of interest of the 287 authors listed in the bylines. Five (8%) studies had authors with industry affiliation. All studies except two (3%) were published in journals that use peer review, and one was published in a journal supplement. The bibliographic references are given in the Supplemental Material (http://www.ehponline.org/members/2006/9149/supplemental.pdf). Blinded and open extraction of data yielded identical results with respect to the reporting of statistically significant effects in the abstract and the message of the title. Study characteristics are shown in Table 1. All studies were published during 1995-2005, with the number of publications increasing from one to two publications per year to 11 publications in 2004. Median year of publication was 1998 for industry-funded studies, 2002 for public or charity funding and studies with mixed funding sources, and 2003 for studies that did not report their funding source. The median size of all the studies was small (20 study participants); most studies (n = 32, 54%) were of a crossover design and mimicked the exposure situation during a phone call, using the 900-MHz band with the antenna located close to the ear. Exposure duration ranged from 3 to 480 min, with a median of 33 minutes. Thirty-three (59%) studies measured outcomes during exposure, 14 (24%) postexposure, and 12 (20%) at both times. Thirty-nine (66%) studies prevented selection bias with adequate randomization randomization (ranˈ·d  ·m ; 15 (25%) blinded
both participants and assessors; in 18 (31%) the field intensity had
been assessed appropriately, with SAR values ranging from 0.03 to 2 W/kg
tissue. Finally, in 14 (24%) studies we considered the statistical
analysis to be adequate. Study quality varied by source of funding:
Studies with mixed funding (including public agencies or charities and
industry) had the highest quality, whereas studies with no reported
source of funding did worst (Table 1).
Forty (68%) studies reported one or more statistically significant results (p < 0.05) indicating an effect of the exposure (Table 2). Studies funded exclusively by industry reported on the largest number of outcomes but were less likely to report statistically significant results: The OR for reporting at least one such result was 0.11 (95% CI, 0.02-0.78), compared with studies funded by public agencies or charities (Table 3). This finding was not materially altered in analyses adjusted for the number of outcomes reported, study design and quality, exposure characteristics, or outcomes [Table 3; see Supplemental Material, Table 1 (http://www.ehponline.org/members/2006/9149/supplemental.pdf)]. Similar results were obtained when restricting analyses to results reported in abstracts (OR = 0.29; 95% CI, 0.05-1.59) or on the conclusions in the abstract (OR = 0.10, 95% CI, 0.009-1.10). Thirty-seven (63%) studies had a neutral title, 11 (19%) a title reporting an effect, and 11 (19%) a title reporting no effect (Table 2). Discussion We examined the methodologic quality and results of experimental studies investigating the effects of the type of radiofrequency radiation emitted by handheld cellular telephones. We hypothesized that studies would be less likely to show an effect of the exposure if funded by the telecommunications industry, which has a vested interest Vested Interest A financial or personal stake one entity has in an asset, security, or transaction. Notes: For example, if you have a mortgage, your bank has a vested interest on the sale of your house. See also: Right in portraying the use of mobile phones as safe. We found that the studies funded exclusively by industry were indeed substantially less likely to report statistically significant effects on a range of end points that may be relevant to health. Our findings add to the existing evidence that single-source sponsorship is associated with outcomes that favor the sponsors' products (Bekelman et al. 2003; Davidson 1986; Lexchin et al. 2003; Stelfox et al. 1998). Most previous studies of this issue were based on studies of the efficacy and cost-effectiveness of drug treatments. A recent systematic review and meta-analysis showed that studies sponsored by the pharmaceutical industry were approximately four times more likely to have outcomes favoring the sponsor's drug than studies with other sources of funding (Lexchin et al. 2003). The influence of the tobacco industry on the research it funded has also been investigated (Barnes and Bero 1996, 1998; Bero 2005). To our knowledge, this is the first study to examine this issue in the context of exposure to radiofrequency electromagnetic fields. Our study has several limitations. We restricted our analysis to human laboratory studies. This resulted in a more homogenous homogenous - homogeneous set of studies, but may have reduced the statistical power to demonstrate or exclude smaller associations. The WHO has identified the need for further studies of this type to clarify the effects of radiofrequency exposure on neuroendocrine neuroendocrine /neu·ro·en·do·crine/ (-en´do-krin) pertaining to neural and endocrine influence, and particularly to the interaction between the nervous and endocrine systems. neu·ro·en·do·crine adj. , neurologic neurologic /neu·ro·log·ic/ (-loj´ik) pertaining to neurology or to the nervous system. Neurologic Having to do with the nervous system. , and immune systems immune system Cells, cell products, organs, and structures of the body involved in the detection and destruction of foreign invaders, such as bacteria, viruses, and cancer cells. Immunity is based on the system's ability to launch a defense against such invaders. (Foster and Repacholi 2004). We considered including epidemiologic studies epidemiologic study A study that compares 2 groups of people who are alike except for one factor, such as exposure to a chemical or the presence of a health effect; the investigators try to determine if any factor is associated with the health effect but found that practically all of them were publicly funded. The study's primary outcome--the reporting of statistically significant associations--is a crude measure that ignores the size of reported effects. However, we found the same trends when assessing the authors' conclusions in the abstracts. Although we have shown an association between sponsorship and results, it remains unclear which type of funding leads to the most accurate estimates of the effects of radiofrequency radiation. For example, if researchers with an environmentalist environmentalist a person with an interest and knowledge about the interaction of humans and animals with the environment. agenda are more likely to be funded by public agencies or charities, then their bias may result in an overestimation o·ver·es·ti·mate tr.v. o·ver·es·ti·mat·ed, o·ver·es·ti·mat·ing, o·ver·es·ti·mates 1. To estimate too highly. 2. To esteem too greatly. of effects. Interestingly, studies with mixed funding were of the highest quality. The National Radiological Protection Board The National Radiological Protection Board is a UK public body set up under the Radiological Protection Act of 1970 with the purpose of disseminating information about the protection of mankind from radiation hazards. (NRPB NRPB National Radiological Protection Board (UK) NRPB National Resources Planning Board (WWII) NRPB National Radiological Protection Directorate 2004) reviewed studies of health effects from radiofrequency (RF) fields and concluded that "scientific evidence regarding effects of RF field exposure from mobile phones on human brain activity and cognitive function ... has included results both supporting and against the hypothesis of an effect." We found that the source of funding explains some of the heterogeneity het·er·o·ge·ne·i·ty n. The quality or state of being heterogeneous. heterogeneity the state of being heterogeneous. in the results from different studies. The association was robust and little affected by potential confounding factors such as sample size, study design, or quality. Possible explanations for the association between source of funding and results have been discussed in the context of clinical research sponsored by the pharmaceutical industry (Baker et al. 2003; Bekelman et al. 2003; Lexchin et al. 2003). The association could reflect the selective publication of studies that produced results that fitted the sponsor's agenda. Sponsors might influence the design of the study, the nature of the exposure, and the type of outcomes assessed. In multivariate The use of multiple variables in a forecasting model. logistic regression analysis, the only factor that strongly predicted the reporting of statistically significant effects was whether or not the study was funded exclusively by industry. We stress that our ability to control for potential confounding factors may have been hampered by the incomplete reporting of relevant study characteristics. Medical and science journals are implementing policies that require authors to disclose their financial and other conflicts of interest. None of the articles examined here included such a statement, in line with a survey of science and medical journals that showed that adopting such policies does not generally lead to the publication of disclosure statements (Krimsky and Rothenberg 2001). A review of 2005 instructions to authors showed that 15 (48%) of the 31 journals included in our study had conflict of interest policies. Our results support the notion that disclosure statements should be published, including statements indicating the absence of conflicts of interest. The role of the funding source in the design, conduct, analysis, and reporting of the study should also be addressed. There is widespread concern regarding the possible health effects associated with the use of cellular phones, mobile telephone base stations, or broadcasting transmitters. Most (68%) of the studies assessed here reported biologic effects. At present it is unclear whether these biologic effects translate into relevant health hazards health hazard Occupational safety Any agent or activity posing a potential hazard to health. Cf Physical hazard. . Reports from national and international bodies have recently concluded that further research efforts are needed, and dedicated research programs have been set up in the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. , Germany, Denmark, Hungary, Switzerland, and Japan. Our study indicates that the interpretation of the results from existing and future studies of the health effects of radiofrequency radiation should take sponsorship into account. 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Classes of antidepressants include selective serotonin reuptake inhibitors (fluoxetine/Prozac, sertraline/Zoloft), tricyclics (amitriptyline/ Elavil), MAOIs (phenelzine/Nardil), and heterocyclics . Br J Psychiatry psychiatry (səkī`ətrē, sī–), branch of medicine that concerns the diagnosis and treatment of mental, emotional, and behavioral disorders, including major depression, schizophrenia, and anxiety. 183:498-506. Barnes D, Bero L. 1996. Industry-funded research and conflict of interest: an analysis of research sponsored by the tobacco industry through the center for indoor air research. J Health Polit Policy Law 21:515-542. Barnes D, Bero L. 1998. Why review articles on the health effects of passive smoking reach different conclusions. JAMA JAMA abbr. Journal of the American Medical Association 279:1566-1570. Bekelman JE, Li Y, Gross CP. 2003. Scope and impact of financial conflicts of interest in biomedical research Biomedical research (or experimental medicine), in general simply known as medical research, is the basic research or applied research conducted to aid the body of knowledge in the field of medicine. : a systematic review. JAMA 289:454-465. Bero L. 2005. Tobacco industry manipulation of research. Public Health Rep 120:200-208. Besset A, Espa F, Dauvilliers Y, Billiard bil·liard adj. Of, relating to, or used in billiards. n. See carom. Adj. 1. billiard - of or relating to billiards; "a billiard ball"; "a billiard cue"; "a billiard table" M, de Seze R. 2005. No effect on cognitive function from daily mobile phone use. Bioelectromagnetics 26:102-108. Croft RJ, Chandler JS, Burgess BURGESS. A magistrate of a borough; generally, the chief officer of the corporation, who performs, within the borough, the same kind of duties which a mayor does in a city. In England, the word is sometimes applied to all the inhabitants of a borough, who are called burgesses sometimes it AP, Barry RJ, Williams JD, Clarke AR. 2002. Acute mobile phone operation affects neural function in humans. Clin Neurophysiol 113:1623-1632. Davidson R. 1986. Source of funding and outcome of clinical trials. J Gen Intern intern /in·tern/ (in´tern) a medical graduate serving in a hospital preparatory to being licensed to practice medicine. in·tern or in·terne n. Med 1:155-158. ELMAR. 2005. Dokumentationsstelle ELMAR, Elektromagnetische Strahlung und Gesundheit ge·sund·heit interj. Used to wish good health to a person who has just sneezed. [German, health, from Middle High German gesuntheit, from gesunt, healthy . Available: www.elmar.unibas.ch [accessed 10 February 2005]. Feychting M, Ahlbom A, Kheifets L. 2005. EMF and health. Annu Rev Public Health 26:165-189. Foster KR, Repacholi MH. 2004. 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Available: http://www.hpa.org.uk/radiation/publications/documents_of_nrpb/pdfs/doc_14_2.pdf [accessed 3 July 2006]. Repacholi MH. 1998. Low-level exposure to radiofrequency electromagnetic fields: health effects and research needs. Bioelectromagnetics 19:1-19. Rothman KJ. 2000. Epidemiological epidemiological emanating from or pertaining to epidemiology. epidemiological associations the associative relationships between the frequency of occurrence of a disease and its determinants, its predisposing and precipitating evidence on health risks of cellular telephones. Lancet lancet /lan·cet/ (lan´set) a small, pointed, two-edged surgical knife. lan·cet n. 356:1837-1840. Stelfox H, Chua G, O'Rourke K, Detsky A. 1998. Conflict of interest in the debate over calcium-channel antagonists antagonists, n muscles that counterbalance agonists during specific movements. opioid Neurology A pain-attenuating peptide that occurs naturally in the brain, which induces analgesia by mimicking endogenous opioids at opioid . N Engl J Med 338:101-106. Thompson DF. 1993. Understanding financial conflicts of interest. N Engl J Med 329:573-576. Yaphe J, Edman R, Knishkowy B, Herman J. 2001. The association between funding by commercial interests and study outcome in randomized controlled drug The United Kingdom Misuse of Drugs Act 1971 aimed to control the possession and supply of numerous listed drugs and drug-like substances. The act allowed and regulated the use of some Controlled Drugs (designated CD) by various classes of persons (e.g. trials. Fam Pract 18:565-568. Anke Huss, (1) Matthias Egger, (1,2) Kerstin Hug, (3) Karin Huwiler-Muntener, (1) and Martin Roosli (1) (1) Department of Social and Preventive Medicine The Department of Social and Preventive Medicine (popularly known as SPM) is one of 22 teaching departments in the Faculty of Medicine, University of Malaya. It was formed in 1964, one year after the founding of the Faculty of Medicine in the University of Malaya in Kuala Lumpur. , University of Berne, Berne, Switzerland; (2) Department of Social Medicine, University of Bristol, United Kingdom; (3) Institute of Social and Preventive Medicine preventive medicine, branch of medicine dealing with the prevention of disease and the maintenance of good health practices. Until recently preventive medicine was largely the domain of the U.S. , University of Basle, Basle, Switzerland Address correspondence to M. Egger, Department of Social and Preventive Medicine, Finkenhubelweg 11, University of Berne, Switzerland. Telephone: 41-31-631-35-01. Fax: 41-31-631-35-20. E-mail: egger@ispm.unibe.ch Supplemental Material is available online at http://www.ehponline.org/members/2006/9149/supplemental.pdf This study was funded by intramural intramural /in·tra·mu·ral/ (-mu´r'l) within the wall of an organ. in·tra·mu·ral adj. Occurring or situated within the walls of a cavity or organ. funds of the Department of Social and Preventive Medicine, University of Berne, Switzerland. The authors declare they have no competing financial interests. Received 7 March 2006; accepted 15 September 2006.
Table 1. Characteristics of 59 experimental studies of the effects of
exposure to low-level radiofrequency electromagnetic fields.
Source of funding
Industry Public or charity
Study characteristic (n = 12) (n = 11) (n = 14)
Study design [no. (%)]
Crossover trial 10 (83.3) 7 (63.6)
Parallel group trial 0 (0) 2 (18.2)
Other, unclear 2 (16.7) 2 (18.2)
Exposure [no. (%)]
Location of antenna
Next to ear 4 (33.3) 8 (72.7)
Other/unclear 8 (66.7) 3 (27.3)
Frequency band (a)
900 MHz 11 (91.7) 8 (72.7)
Other frequencies 2 (16.7) 7 (63.6)
Unclear 0 (0) 0 (0)
Median duration of exposure (range) 180 (3-480) 20 (5-35)
Outcomes assessed [no. (%)] (a)
Electroencephalogram 7 (58.3) 5 (45.5)
Cognitive function tests 0 (0) 3 (27.3)
Hormone levels 5 (41.7) 0 (0)
Cardiovascular function 2 (16.7) 1 (9.1)
Well-being or symptoms 1 (8.3) 1 (9.1)
Other 4 (33.3) 3 (27.3)
Study quality [no. (%)] (a)
Randomization adequate 10 (83.3) 7 (63.6)
Participants and assessors blinded 1 (8.3) 3 (27.3)
SAR determined 4 (33.3) 4 (36.4)
Statistical analysis adequate 3 (25) 3 (27.3)
Median study size (range) 21 (8-38) 24 (13-100)
Source of funding
Mixed Not reported
Study characteristic (n = 14) (n = 22)
Study design [no. (%)]
Crossover trial 12 (85.7) 11 (50)
Parallel group trial 1 (7.1) 2 (9.1)
Other, unclear 1 (7.1) 9 (40.9)
Exposure [no. (%)]
Location of antenna
Next to ear 11 (78.6) 14 (63.6)
Other/unclear 3 (21.4) 8 (36.4)
Frequency band (a)
900 MHz 13 (92.9) 14 (63.6)
Other frequencies 0 (0) 5 (22.7)
Unclear 1 (7.1) 5 (22.7)
Median duration of exposure (range) 45 (30-240) 30 (4-480)
Outcomes assessed [no. (%)] (a)
Electroencephalogram 8 (57.1) 12 (54.5)
Cognitive function tests 8 (57.1) 8 (36.4)
Hormone levels 0 (0) 2 (9.1)
Cardiovascular function 0 (0) 2 (9.1)
Well-being or symptoms 1 (7.1) 0 (0)
Other 1 (7.1) 3 (13.6)
Study quality [no. (%)] (a)
Randomization adequate 13 (92.9) 9 (40.9)
Participants and assessors blinded 8 (57.1) 3 (13.6)
SAR determined 8 (57.1) 2 (9.1)
Statistical analysis adequate 7 (50) 1 (4.5)
Median study size (range) 20 (13-96) 20 (8-78)
Percentages are column percentages.
(a) The same study could be listed in more than one category.
Table 2. Results from assessments of article text, abstract, and title
of 59 experimental studies of the effects of exposure to low-level
radiofrequency electromagnetic fields.
Source of funding
Industry Public or charity
(n = 12) (n = 11)
Article text
No. (%) of studies with at 4 (33) 9 (82)
least one result suggesting
an effect at p < 0.05
Median no. (range) of 17.5 (4-31) 10 (1-80)
outcomes reported
Median no. (range) of 0 (0-6) 1.5 (0-7)
outcomes suggesting an
effect at p < 0.05
Abstract (a) (n = 12) (n = 11)
No. (%) of studies with at 4 (33) 7 (64)
least one result suggesting
a significant effect
Median no. (range) of 3.5 (1-36) 3 (1-5)
outcomes reported
Median no. (range) of 0 (0-6) 1 (0-3)
outcomes suggesting
a significant effect
Authors' interpretation of
results [no. (%)]
No effect of radiofrequency 10 (83.3) 5 (45.5)
radiation
Effect of radiofrequency 1 (8.3) 5 (45.5)
radiation
Unclear finding 1 (8.3) 1 (9)
Title [no. (%)]
Neutral 7 (58) 5 (46)
Statement of effect 0 (0) 4 (36)
Statement of no effect 5 (42) 2 (18)
Source of funding
Mixed Not reported
(n = 14) (n = 22)
Article text
No. (%) of studies with at 10 (71) 17 (77)
least one result suggesting
an effect at p < 0.05
Median no. (range) of 16 (9-44) 7 (1-35)
outcomes reported
Median no. (range) of 3 (0-15) 1.5 (0-12)
outcomes suggesting an
effect at p < 0.05
Abstract (a) (n = 14) (n = 20)
No. (%) of studies with at 10 (71) 15 (75)
least one result suggesting
a significant effect
Median no. (range) of 6.5 (3-44) 3 (1-64)
outcomes reported
Median no. (range) of 2 (0-5) 1.5 (0-7)
outcomes suggesting
a significant effect
Authors' interpretation
of results [no. (%)]
No effect of radiofrequency 4 (28.6) 5 (22.7)
radiation
Effect of radiofrequency 8 (57.1) 14 (63.6)
radiation
Unclear finding 2 (14.3) 3 (13.6)
Title [no. (%)]
Neutral 8 (57) 17 (77)
Statement of effect 3 (21) 4 (18)
Statement of no effect 3 (21) 1 (5)
Percentages are column percentages.
(a) Two publications that did not report their source of funding had no
abstracts.
Table 3. Probability of reporting at least one statistically significant
result (p < 0.05) according to source of funding: crude and adjusted ORs
(95% CIs) from logistic regression models.
Source of funding
Industry Public or charity
(n = 12) (n = 11)
Crude 0.11 (0.02-0.78) 1 (reference)
Adjusted for
No. of reported 0.12 (0.02-0.89) 1 (reference)
outcomes
Median study size 0.08 (0.009-0.62) 1 (reference)
Study design 0.08 (0.01-0.68) 1 (reference)
(crossover,
parallel, or other)
Study quality
Randomization 0.04 (0-0.56) 1 (reference)
adequate
Participants and 0.14 (0.02-0.96) 1 (reference)
assessors blinded
Statistical analysis 0.12 (0.02-0.85) 1 (reference)
adequate
Exposure setting 0.13 (0.02-0.89) 1 (reference)
appropriate
Source of funding
Mixed Not reported
(n = 14) (n = 22) p-Value (a)
Crude 0.56 (0.08-3.80) 0.76 (0.12-4.70) 0.04
Adjusted for
No. of reported 0.60 (0.08-4.28) 0.96 (0.15-6.23) 0.04
outcomes
Median study size 0.61 (0.08-4.59) 0.57 (0.08-4.02) 0.02
Study design 0.38 (0.05-3.07) 1.16 (0.16-8.61) 0.029
(crossover,
parallel, or other)
Study quality
Randomization 0.16 (0.01-2.15) 1.27 (0.16-9.89) 0.005
adequate
Participants and 0.54 (0.08-3.91) 0.76 (0.12-4.8) 0.09
assessors blinded
Statistical analysis 0.67 (0.09-4.85) 0.54 (0.08-3.76) 0.07
adequate
Exposure setting 0.47 (0.07-3.39) 0.86 (0.14-5.5) 0.06
appropriate
Models adjusted for one variable at a time.
(a) From likelihood ratio tests.
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