Rapid Responses to:
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Rapid Responses: Rapid Responses published:
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Minimising Bias
- Corinne Powell (20 January 2006)
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Amateur Radio Response
- Sheldon L. Epstein (21 January 2006)
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Mobile phone use and risk of gioma in adults: case-control study
- Samuel Milham, Indio CA USA 92201 (21 January 2006)
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Bias
- Daniel Reicher (22 January 2006)
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Main conclusion is not justified
- Alasdair M Philips (23 January 2006)
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Re: Amateur Radio Response
- Samuel Milham (24 January 2006)
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Conclusions on glioma risk of mobile phone use questionable
- Michael Kundi (25 January 2006)
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Re: Amateur Radio Response
- John P Heptonstall Graduate mathematician and physicist (28 January 2006)
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Low Participation Rates/Exposed Reference Group/Conflict-of-Interest
- L. Lloyd Morgan (28 January 2006)
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Re: Low Participation Rates/Exposed Reference Group/Conflict-of-Interest
- David Bücher (30 January 2006)
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Mobile phone use and risk of glioma in adults: case-control study.
- bruce hocking (3 February 2006)
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Re: Mobile phone use and risk of glioma in adults: case-control study
- Lennart Hardell, Lennart Hardell, Kjell Hansson Mild (20 April 2006)
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Selective Recall Bias?
- Bart J. Harvey (21 May 2006)
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Cell Phones Protective Against Glioma--Alternate Explanation
- Eric L yarnell (15 February 2007)
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Mobile Phone use and oliodendroglioma
- Suki Rai (30 January 2008)
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Corinne Powell, Teacher of Maths (Statistics) William Parker Sports College Hastings E. Sussex TN34 2NT
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In the period from 1 December 2000 to 29 February 2004 could there have been any deaths of people diagnosed with a glioma in the population? Clearly, if this were the case, such people would be excluded from the sampling frame leading to biased reults. Many thanks Corinne Powell Competing interests: None declared |
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Sheldon L. Epstein, Electrical Engineer 60091
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The study results are consistent with almost 100-years of Amateur Radio operator experience. In the USA, hand-held cellphone power is limited to 0.6-watt. By comparison, Amateur Radio handheld transceivers typically have 5-watts of power and a few models have 7-watts of power. While the Amateur Radio transceivers operate on frequencies that are lower that those of cellphones, neither class of devices generated ionizing radiation. The Amateur Radio community in the United States comprises approximately 350,000 active operators. Radiation safety is now a required subject in both license examinations and Federal Communications Commission rules for station operation best practices. Thus, Amateur Radio operators have been sensitized to be alert to the possibity of medical consequences caused by unsafe transmitter operation. Yet with all of these warnings, there is no evidence - anecdotal or otherwise - that a physical presence near low power radio transmitters or antennae causes any adverse medical consequence to Amateur Radio operators. The same appears to be true for police, fire, paramedic and other employees who regularly use similar radios and yet have not filed any significant number of claims for work-related injuries. The only case that received any publicity to catch my notice was filed by a police officer who claimed he had testicular cancer because he left his radar gun on and in his lap while he was on patrol. In conclusion, residents of major metropolitan areas live in a veritable sea of radio-frequency energy. Despite this, there is no epidemological evidence that continuous exposure to low amounts of electromagnetic energy plays any role in causing cancer. Competing interests: None declared |
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Samuel Milham, retired physician/epidemiologist 82181 Bergman Dr 92201, Indio CA USA 92201
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In tables 2 and 3 of this recently published study by Hepworth et al (1), there are 37 calculated odds ratios, with only 5 above 1.0 and 32 below 1.0. If cell phone use is not related to glioma development, I'd expect as many odds ratios above as below 1.0. These findings suggest either that cell phone use protects against glioma or that exposure assessement is faulty. With a 57% non-response rate in the control group and greater affluence in the interviewed controls, I think that the interviewed controls were more often cell phone users. The fact that many of the non-interviewed controls were never contacted, may be because they didn't use cell phones. The positive odds ratio for ipsilateral cell phone use and glioma risk is similar to that found by Lonn et. al. (2) in another basically negative cell phone/brain tunour study, and should not be dismissed as due to recall bias. With so much riding on studies like this one, it's a mystery to me how they get published with more non- participating than participating controls and every reaon to suspect systematic non-response bias. References 1.Hepworth SJ, Schoemaker MJ, Muir KR, et. al. Mobile phone use and risk of glioma in adults: case-control study BMJ Jan 2006; doi:10.1136/bmj.38720.687975.55. 2.Lonn S, Ahlbom A, Hall P et. al. Long term mobile phone use and brain tumour risk Am. J. Epidemiology 2005; 161;526-535. Competing interests: None declared |
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Daniel Reicher, Retired. H3T 1G7
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A study partly funded by the manufacturers of cell phones is in a position of competing interest. Competing interests: None declared |
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Alasdair M Philips, Researcher Cambridgeshire, CB6 2QA
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The authors of this paper claim: "Use of a mobile phone, either in the short or medium term, is not associated with an increased risk of glioma." I do not believe that such a generalised conclusion can be drawn from their data. The paper states that only 51% of the indentified glioma cases were able to be included in the analysis. 30%, mostly with high grade gliomas, had "died or were too ill to interview", and the authors admit that "participation rates were higher in those with low grade tumours". The authors state that they tested for bias, and found none, but fail to present the raw data or the numerical basis for this dismissive claim. Another concern that I have is that the reference group (used to set the base Odds Ratio at 1.00) not only contained people who had never used a mobile phone but also "non-regular" users and cordless phone users. Since the power output from cordless phones are fixed to about 10mW mean and GSM phones often operate at a lower output that this, people subject to a significant exposure source have been included in the reference group. The papers analysing Swedish brain tumour data [1,2] show a clear association of brain tumour incidence with at least five years regular use, increasing with ten years use for both mobile and cordless phones. If there is a link to be found, then the effect of including these people in the reference group would have been to skew the dataset and move all the Odds Ratios down towards unity. As high grade gliomas are often fatal within a short time of diagnosis, it is clear that a prospective study is now needed that will record details of cases as they are diagnosed. The mobile phone operators should be obliged to keep and release phone usage date for such epidemiological analysis - it is not adequate to rely on patients memories as that will greatly reduce the resolving power of any study. As this study was funded jointly by the Government and the Mobile Phone Industry via the Mobile Telephone Health Research group, it is disappointing that it was not more rigorous. Alasdair Philips
1. Hardell L, et al, Cellular and cordless telephones and the risk for brain tumours, Eur J Cancer Prev 2002;11:377-386 2. Hardell L, Hansson Mild K and Carlberg M, Further aspects on cellular and cordless phones and brain tumours, International Journal of Oncology, 22:399-407, 2003. Competing interests: Powerwatch acts as a public information resource regarding EMFs and health and has some commercial activities to fund its work. For more details, see: www.powerwatch.org.uk |
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Samuel Milham, retired physician/epidemiologist 82181 Bergman Dr Indio CA 92201
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1: Am J Epidemiol. 1988 Jan;127(1):50-4. Related Articles, Links Increased mortality in amateur radio operators due to lymphatic and hematopoietic malignancies. Milham S Jr. Epidemiology Section, Washington State Department of Social and Health Services, Olympia 98504. To search for potentially carcinogenic effects of electromagnetic field exposures, the author conducted a population-based study of mortality in US amateur radio operators. Ascertainment of Washington State and California amateur radio operators (67,829 persons) was done through the 1984 US Federal Communications Commission Amateur Radio Station and/or Operator License file. A total of 2,485 deaths were located for the period from January 1, 1979 through December 31, 1984, in a population of amateur radio operators which accumulated 232,499 person-years at risk. The all- cause standardized mortality ratio (SMR) was 71, but a statistically significant increased mortality was seen for cancers of the other lymphatic tissues (SMR = 162), a rubric which includes multiple myeloma and non-Hodgkin's lymphomas. The all-leukemia standardized mortality ratio was slightly, but nonsignificantly, elevated (SMR = 124). However, mortality due to acute myeloid leukemia was significantly elevated (SMR = 176). PMID: 3422125 [PubMed - indexed for MEDLINE] Competing interests: None declared |
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Michael Kundi, Head of Institute Institute of Environmental Health, Center for Public Health, Medical University of Vienna, Austria
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The study by Hepworth et al. (1) is a thoroughly planned investigation of the potential association between glioma and mobile phone use. It has an interesting methodological aspect in that it utilized records of general practitioners for the selection of control subjects. However, there are severe shortcomings of conduction, analysis and report including faulty interpretations and unfounded conclusions. Do authors really think that there is any occupational or environmental factor on earth capable of inducing glioma within a period of 3 to 4 years (the average duration of use of a mobile phone in this study)? Not even after high doses of therapeutic x-rays (2,3) such short latencies have been observed. There are only 5% of cases with a duration of mobile phone use that reaches or exceeds 10 years. Therefore, it is completely out of question that induction of glioma can be studied. Only an effect on tumour development and growth can possibly be detected. As pointed out earlier (4,5) the case-control design is inefficient to study such effects if duration of exposure is short. Furthermore, if an effect on an already pre -malignant lesion is studied only exposures to that region are exposures at all. Therefore the only relevant analysis is that of laterality. And, surprisingly, this analysis resulted in a significantly increased risk that increased further if longer exposure durations were considered. Hence the only analysis compatible with the natural history of the disease and exposure conditions showed a significantly increased risk. But still the authors conclude: “This…study found no increased risk of developing a glioma associated with mobile phone use…” Authors point to the fact that the odds-ratio for contralateral exposure is below one and seem to interpret this as an indication for recall bias. However, they seem not to be aware that this is simply a consequence of their method of analysis and of the significant effect on the ipsilateral side. 1 Hepworth SJ, Schoemaker MK, Muir KR, Swerdlow AJ, van Tongeren MJA, McKinney PA. Mobile phone use and risk of glioma in adults: case- control study. BMJ, doi:10.1136/bmj.38720.667975.55 (published 20 January 2006) 2 Simmons NE, Laws ER Jr. Glioma occurrence after sellar irradiation: case report and review. Neurosurgery 1998, 42:172-178. 3 Kranzinger M, Jones N, Rittinger O, Pilz P, Piotrowski WP, Manzl M et al. Malignant glioma as a secondary malignant neoplasm after radiation therapy for craniopharyngioma – Report of a case and review of reported cases. Onkologie 2001; 24:66-72. 4 Kundi M. Mobile phone use and cancer. Occup Environ Med 2004; 61:560-570. 5 Kundi M, Hanson Mild K, Hardell L, Mattsson M-O. Mobile telephones and cancer – A review of epidemiological evidence. J Toxicol Environ Health B 2004; 7:351-384. Competing interests: None declared |
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John P Heptonstall Graduate mathematician and physicist, Director of the Morley Acupuncture Clinic Leeds LS27 8EG
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Sir Sheldon L. Epstein perhaps accurately reflects the current scientific position as regards ionising radiation as a causative agent in brain cancers - although I think the study has numerous possible flaws some of which have been highlighted by other responders. However, I note that Sheldon was careful to mention only ionising radiation, yet radios and radio telephones carry another probable risk form non-ionising radaition and, having measured the continuous bursts of high level (>100 milligauss - the limit of the measuring equipment I was using - a Trifield Meter) electromagnetic radiation emitted by such equipments when transmitting and receiving I suggest that this radiation carries hazards which are, as yet, not properly described in well-quoted research into mobile phone use by scientists or engineers who have confined the discussion so often to ionising radiation. The same arguments take place over mobile phone mast sites. For some I have witnessed, and one in particular I advised on some years ago, persons who believed they had developed adverse reactions to adjacent mobile phone masts (eg. medically confirmed neurological for which the specialist could offer no explanation as to cause) were informed by engineers and scientists comissioned to investigate that ionising radiation could not be the cause as hotspots, though identified as being present in the building in question, were not impacting directly on the complainant's location and originated from another mobile phone mast located in another part of town! The mast present adjacent to the complainant, on a roof 8 feet above head height, would however be emitting high levels of electromagnetic radiation when in use which could impact on the location in question and might be the cause of the neurological problems that developed soon after the mast was installed. Regards John H. Competing interests: None declared |
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L. Lloyd Morgan, Electronic Engineer (retired) 2022 Francisco St., Berkeley, CA 94709
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In years past, this paper would never have been published because such a low participation rate of cases and controls would have, by itself, been a cause for rejection. With only 51% of glioma victims (30% had died by the time they were contacted) and 45% of the controls (29% refused to participate) participating, combined with more affluent controls than cases, there is little reason to believe any of the reported results. Affluent participating controls are more likely to use cellphones than the non-participating controls. Such a “selection bias” would result in an underestimation of the risk of glioma from cellphone use. The sheer proportion of non-participating controls makes such selection bias highly probable. The study would seem to suggest that using a cellphone would protect the cellphone use from the risk of glioma. If there is no risk of glioma from cellphone use, then there would be about the same number of odds ratios greater than one (increased risk) as there would be odds ratios less than one (reduced risk). Overall this study reports 34 odds ratios greater than one to 8 odds ratios less than one. This is equivalent to saying if I flip a coin 42 times, what is the chance that I will get 34 heads and 8 tails. Such a probability can be calculated. The probability that cellphone use protects the user from glioma is 99.997%. There are only two possible conclusions. Either cellphone use protects the user from glioma, or the study is flawed. You, the reader, must choose between these two possibilities. There is no other choice possible. In spite of these incredible flaws, the study did report a 60% increased risk of glioma for regular cellphone use of 10 years or more on the same side of the head as the location of the tumor. Hardell et al. (Environmental Research 12 July 2005) reported for wireless phone use on the same side of the head, the risk of high-grade astrocytoma was 4.2, 3.2 and 4.0 for analog and digital cellphone and cordless phone use, respectively. The Hepworth et al. paper did not reference this study (even though it was published some 4 months prior to acceptance of the Hepworth paper.) has found similar results, though with much higher risk of glioma. The reference group for this study’s findings is “Never/non-regular” cellphone users. Because this reference group did not exclude the users of cordless (DECT) phones the reference group cannot be described as unexposed. Hardell et al.(July 2005)reported that cordless phone users who did not use cellphone are at risk of high-grade astrocytoma (OR=1.9, CI; 1.01-3.5). Finally, it is important to understand that this study, as is true with every Interphone study, has received substantial funding from the cellphone industry. Though the study reports that this funding “ensures complete independence for the scientific investigators,” this is inherently not possible. Researchers careers are dependent on receiving research grants. Even with isolation of funding for a specific study from the researchers themselves, the conflict-of-interest in such funding is not resolved. Because the researchers know where the funding has come from, the old adage, “Don’t bite the hand that feeds you” becomes the effective psychological reality (whether conscious or unconscious). This same conflict-of-interest issue can be seen within the United States Government's Federal Drug Administration (FDA) where pharmaceutical companies pay fees for drug approval isolated from specific research projects. It is quite apparent that the FDA has come to see the pharmaceutical industry as their customer, not the American public. Also to note: just like the pharmaceutical industry-funded studies, industry-funded cellphone studies will not release their protocols--so that there is limited assurance both as to the validity of their study procedures and the steps take to shield research from economic interests. For example, the Interphone study protocol, a common protocol used by 13 participating countries, is kept “strictly confidential.” While there is a process to maintain the independence of researchers from direct cellphone industry involvement, it is unclear as to what and how the cellphone industry was involved in the Interphone study protocol design. Certainly, the Interphone definition of “regular” cellphone use is set to such a minimal standard that few could imagine a finding of risk. Regular cellphone use is defined as cellphone use for at least once a week for six months or more, a year prior to the study cutoff date. The important question to ask is, if this were a study of the risk of lung cancer from smoking would there be a likelihood of finding a risk of lung cancer from smokers who had smoked at least once a week for 6 months or more, a year prior to the study cutoff date? And, would there be a finding of risk, if as is the case in this study for cellphone use, the lifetime years of smoking for 10 years or more included only 3.9% of the smokers in the study? Competing interests: None declared |
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David Bücher, student of mathematics Darmstadt, Germany
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L. Lloyd Morgan's calculation is not valid since it assumes that the odds ratios are stochastically independent, which they are presumably not. But further support for the type of selection bias suggested by Samuel Milham and L. Lloyd Morgan comes from other parts of the Interphone study: According to Lahkola et al. [1], participation proportions in the Finnish part were 46% among controls and 84% among cases. Cellular phone usage was more prevalent in participants than in incomplete participants (those not willing to give a full personal but a brief telephone interview). When incomplete participants were included, the odds ratio for brain tumors and regular mobile phone use rose from 0.55 (CI: 0.39 - 0.77) to 0.73 (CI: 0.56 - 0.96). Also mobile phone numbers were less likely available for totally refusing controls (who even declined a telephone interview) than for participating controls. Similarly, results of a nonresponder questionnaire indicated a lower proportion of cell phone users among nonresponders (but responders to the nonresponder questionnaire) than among responders in the German Interphone part [2]. 1. Lahkola A, Salminen T, Auvinen A. Selection bias due to differential participation in a case-control study of mobile phone use and brain tumors. Ann Epidemiol. 2005 May;15(5):321-5. http://www.annalsofepidemiology.org/article/PIIS1047279705000116/abstract 2. Schüz J, Böhler E, Berg G, Schlehofer B, Hettinger I, Schlaefer K, Wahrendorf J, Kunna-Grass K, Blettner M. Cellular Phones, Cordless Phones, and the Risks of Glioma and Meningioma (Interphone Study Group, Germany). Am J Epidemiol. 2006 Jan 27; [Epub ahead of print] http://aje.oxfordjournals.org/cgi/content/abstract/kwj068v1 Competing interests: None declared |
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bruce hocking, specialist in occupational medicine 9 tyrone St , camberwell. Vic. Australia.
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Hepworth et al (1) have conducted a case-control study to assess the risk of glioma in relationship to mobile phone use in 966 cases and 1716 controls selected from general practitioners lists. They found no relation for risk of glioma and time since first use, lifetime years of use, and cumulative number of calls and hours of use. However they found an increased risk for tumour ipsilateral to the side most used, and a parallel reduction in the contralateral side. The study has several problems which limit the confidence that can be placed on the results. 50% of the controls did not participate. In the case of 21% of controls this was due to “non-response”. This failure to contact the subject could have been due to the subject not having a mobile phone and so would bias the control group to include mainly users. In addition the control group who were eventually recruited were more affluent than cases and so better able to afford a mobile phone and to use it more leading to systemic bias in the control data which would mask any effect of phones. 47% of cases did not participate. 37% of the cases were too ill or mentally impaired due to the effects of the tumor or treatments. However the clarity of thought of the remainder was not assessed yet this is critical for accurate recall of data over 10 years. The quality of data collection is entirely dependent on the accuracy of recall by subjects for upto and over 10 years previously, regarding average amount of time use, number of calls, use of hands-free kits and side of head on which the mobile phone was used. The accuracy of the recall of this data is crucial but not substantiated in the paper. There is no reference to cross- checking the recall data with billing data to determine the margins of error regarding phone usage. Recall has been shown to be highly inaccurate compared to billing data. Parslow et al (2) obtained recall data about mobile phone use from 93 volunteers and compared this to their outgoing phone bills over a six- month period. They found only modest correlations and concluded "self reported mobile phone use may not fully represent patterns of mobile phone use". Similar findings have been made by Samkange-Zeeb (3) and colleagues who compared self reported cell phone use with billing data over a three month period. Shum et al (4) surveyed 61 volunteers over a three-year period regarding reported mobile phone use compared to billing data and similarly found the majority were not able to report their duration of use to within +/- 25% of the minutes obtained from billing data. These studies have found problems in recall data over relatively short periods of time, yet Hepworth etal place reliance on accurate recall for upto and over 10 years, even though such recall is likely to be even more unreliable and lead to substantial non-differential misclassification and a null finding. 30% of cases were not interviewed because they were too ill or dead. These subjects are likely to have included the highest grade tumors. Removal of this large number of cases will alter the number of cases available for analysis and so lessen the likelihood of finding a relationship between severity of tumor and use of phone. The study contains serious flaws which lessen the confidence that can be placed on the conclusion of no association of glioma and mobile phone use. Dr Bruce Hocking
References. 1. Hepworth SJ, Schoemaker MJ, Muir KR, Swerdlow AJ, van Tongeren MJ, McKinney PA. Mobile phone use and risk of glioma in adults: case-control study. BMJ. 2006 Jan 20; 2. Parslow RC, Hepworth SJ, McKinney PA (2003) Recall of past use of mobile phone handsets. Radiat Prot Dosimetry.106(3):233-40. 3. Samkange-Zeeb F, Berg G, Blettner M. (2004) Validation of self- reported cellular phone use.J Expo Anal Environ Epidemiol. 14(3):245-8. 4. Shum M, Kelsh M, Zhao K, Erdreich L. Comparison of recall of mobile phone use with billing record data. Proceedings. Bioelectromagnetics Society conference. Dublin. 2005. Competing interests: None declared |
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Lennart Hardell, MD, Professor Department of Oncology, University Hospital, SE-701 85 Orebro, Sweden, Lennart Hardell, Kjell Hansson Mild
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We have read this recently published paper, UK part of the so-called Interphone study, with interest.1 However, the results are difficult to interpret due to several limitations in the study design and analysis. The participation rate was extremely low, for cases 51 % and for controls only 45 %. Furthermore “non-participating controls were replaced” thus with potential for selection bias for the controls. In fact participating controls were more affluent than both non-participating controls and participating cases. There is a clear gradient of mobile phone use as to social class. In our case-control study encompassing answers from 1 254 (88 %) cases with a benign brain tumour, 905 (90 %) cases with a malignant brain tumours and 2 162 (89 %) controls use of cellular telephones was reported by 48 % of the most affluent cases and 36 % in the least affluent group. 2,3 Use of cordless telephones was not assessed in contrast to our studies. The “unexposed” group was thus not truly unexposed to microwaves. The analysis of laterality is doubtful since the “unexposed” group contained subjects with exposure to microwaves on the opposite side of the head than analysed; analysis of ipsilateral exposure with contralateral exposure classified as “unexposed” and analysis of contralateral exposure with ipsilateral exposure classified as “unexposed”. We note that the numbers of interviewed cases are not constant. In the abstract 966 cases are reported but in Table 2 numbers of tumour grade and side of phone use are given for 972 cases, see footnotes. In Table 3 of 14 odds ratios 13 are < 1.0 and one > 1.0 indicating non-random variation and methodological problems in the study. Brain tumour cases may not be ideally interviewed face to face shortly after their operation due to serious cognitive behavioural defects such as memory loss and aphasia. In the Danish Interphone study cases with glioma scored significantly lower than controls due to problems in recalling words (aphasia) and symptoms due to paralysis. 4 These aspects are not at all discussed in the paper.1 In contrast to our studies the interviewers knew if it was a case or a control that was interviewed. As to urban and rural living the investigators seam just to have asked about the study subjects own ideas on that without relying on official statistics. Thus these data are less informative compared with our data where we used the Swedish Population Registry for municipality for all cases and controls and Statistics Sweden for further classification into 6 categories of population density.5 Our latest publication on malignant brain tumours and use of cellular and cordless telephones is not cited although available at internet since July 14, 2005.6 Now results of the pooled analysis of our studies are published.2,3 Clearly we found an increased risk for high-grade astrocytoma using >10 years latency period. It is unfortunate that the current publication does not give results for high-grade and low-grade glioma separately. It is interesting to note that the article cites critics of our studies published even before our results appeared in scientific literature. Two of the cited reports have never been published in a pre- review journal and are thus not possible to rebut. The third cited report was published in 2000, thus even when our first large case-control study was on going and no data had been reported. Furthermore, there seems to be a link to the mobile phone industry among some of the cited authors.7 We note that some of the participating universities and authors have received grants from the telecom industry. Also this study was heavily telecom industry funded. Besides local industry grants in UK the Interphone study according to IARC is funded from industry with 3.5 million Euros, and from the European Union, 3.85 million Euros (E Cardis, personal communication). The contract stipulated that the industry has the right to be informed about the results a maximum of seven days before the publication.8 Receiving grants from industry is by the International Committee of Medical Journal Editor regarded as “the most important conflicts of interest”. In a review of health studies on environmental tobacco smoke the rate ratio of a paper with at least one author with industry associations reaching an industry-favourable conclusion was 3.2, 95 % CI 1.4-7.5.9 It should be noted that one of the authors (Dr Swerdlow) is a member of ICNIRP, a German foundation on this issue that does not recognize any cancerogenesis from microwave exposure. ICNIRP seems to be a closed organisation that elects its own members and without full disclosure how it is financed. Membership might be a conflict of interest. Finally, we do not agree with the statement in the accompanied editorial that “any risk to the individual mobile phone user of developing brain pathology is fleetingly small” and that there is “no need to apply the precautionary principle” for mobile use.10 This is a too premature statement since studies on long term health effects, especially for children, are lacking. Lennart Hardell, MD, PhD, Professor Department of Oncology, University Hospital, SE-701 85 Orebro and Department of Natural Sciences, Orebro University, SE-701 82 Orebro, Sweden Kjell Hansson Mild, PhD, Professor National Institute for Working Life, SE-907 13 Umeå and Department of Natural Sciences, Orebro University, SE-701 82 Orebro, Sweden Correspondence: Dr Lennart Hardell, Department of Oncology, University Hospital, SE-701 85 Orebro, Sweden phone + 46 19 602 15 46, fax + 46 19 10 17 68, e-mail: lennart.hardell@orebroll.se References 1. Hepworth SJ, Schoemaker MJ, Muir KR, Swerdlow AJ, van Tongeren MJA, McKinney PA. Mobile phone use and risk of glioma in adults: case- control study. BMJ 2006;332:883-6. 2. Hardell L, Carlberg M, Hansson Mild K. Pooled analysis of two case -control studies on the use of cellular and cordless telephones and the risk of benign brain tumours diagnosed during 1997-2003. Int J Oncol 2006;28:509-18. 3. Hardell L, Carlberg M, Hansson Mild K. Pooled analysis of two case -control studies on use of cellular and cordless telephones and the risk of malignant brain tumours diagnosed during 1997-2003. Int Arch Occup Env Health 2006; DOI 10.1007/s00420-006-0088-5. 4. Christensen HC, Schüz J, Kosteljanetz M, Poulsen HS, Boice JD, McLaughlin JK, Johansen C. Cellular telephones and risk for brain tumors. A population-based, incident case-control study. Neurology 2005;64:1189- 95. 5. Hardell L, Carlberg M, Hansson Mild K. Use of cellular telephones and brain tumour risk in urban and rural areas. Occup Environ Med 2005;62:390-4. 6. Hardell L, Carlberg M, Hansson Mild K. Case-control study on the association between the use of cellular and cordless telephones and malignant brain tumors diagnosed during 2000-2003. Env Res 2005; DOI: 10.1016/j.envres.2005.04.006 7. Hardell L. From phenoxyacetic acids to cellular telephones: Is there historic evidence of the precautionary principle in cancer prevention? Int J Health Services 2004;4:25-37. 8. IARC (2005) http://www.iarc.fr/ENG/Units/RCAd.html (Assessed April 19, 2006). 9. Garne D, Watson M, Chapman S, Byrne F. Environmental tobacco smoke research published in the journal Indoor and Built Environment and associations with the tobacco industry. Lancet 2005;365:804-9 10. Maier M. Brains and mobile phones. The biggest risk to health from mobile phones is using them while driving. BMJ 2006;332:864-5. Competing interests: None declared |
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Bart J. Harvey, Associate Professor University of Toronto M5T 1W7
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It appears inconsistent for Hepworth and colleagues to implicate recall bias as an explanation for the significant association between glioma risk and the laterality of mobile phone use found by their study. If the subjects with glioma (the cases in this case-control study) were truly affected by recall bias, wouldn't we also expect that the cases’ reporting of overall mobile phone use to be similarly biased? But this is not what was found--the study’s results indicate no association between overall mobile phone use and glioma. How do the authors explain this apparent ‘selective recall bias’ with the reporting of laterality of mobile phone use apparently affected by recall bias, but the reporting of overall mobile phone use being unaffected? Competing interests: None declared |
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Eric L yarnell, Assistant Professor, Dept of Botanical Medicine Bastyr University, Seattle, WA 98028
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Several rapid responses contend that since cell phone use actually appeared protective against glioma, that there are only two choices--either they are actually protective, or the study is flawed. There is in fact another completely rationale explanation, which is that cell phone use is correlated with some other behavior or factor which is protective against glioma, and that the study was simply not designed to detect this external influence. That such a basic premise of epidemiological and correlative research was overlooked in the critical letters is astonishing. Beyond this fact, is it so outlandish to believe that cell phones might actually mitigate the risk of glioma? It seems to me the responses to the study tend to assume that radio waves must be dangerous, despite very limited if any proof of causation (though correlation has been shown in some research and denied in others) of cancer and several other conditions. Anyhow, if radio waves and related energies have biological effects, must they be inherently negative? I do not know but I think there is a lot of jumping to conclusions and bias in this discussion clouding people's reason. Competing interests: I own and use a cell phone regularly. |
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Suki Rai, barrister 3-8 Whitehall Place, London SW1A 2HH
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I read your article with interest but it has not convinced me that my husband's tumour was not due, in some part, to his high mobile phone use. He was 38 years old when the grade II oliodendroglioma was discovered in his right frontal lobe, about the size of a tangerine. The tumour was on his right side, he is right-handed. He has always put his mobile to his right ear - he has used a mobile for about 10 years. The last five of those years were very heavy use as he is self-employed and not fixed to a desk. I feel that there is a real correlation in his case with mobile phone usage but I have no way of proving this. We have no family history of cancer - both his parents are well and his grandparents died of old age. I am particularly concerned about the risk factors for our children who are now at an age where mobile phones are de rigour. Competing interests: None declared |
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