Are wireless phones linked with brain cancer risk?Ronnie Cohen, Reuters Health, Nov 11, 2014
On October 30th, I distributed the following message which contains the study abstract along with my summary of key findings and selected excerpts from the paper by Hardell and Carlberg:
L. Hardell, M. Carlberg, Cell and cordless phone risk for glioma - Analysis of pooled case-control studies in Sweden, 1997-2003 and 2007-2009. Pathophysiology (2014), Available online 29 October 2014. http://dx.doi.org/10.1016/j.
We made a pooled analysis of 2 case-control studies on malignant brain tumours with patients diagnosed during 1997-2003 and 2007-2009. They were aged 20-80 years and 18-75 years, respectively, at the time of diagnosis. Only cases with histopathological verification of the tumour were included. Population-based controls, matched on age and gender, were used. Exposures were assessed by questionnaire. The whole reference group was used in the unconditional regression analysis adjusted for gender, age, year of diagnosis and socio-economic index.
In total 1,498 (89%) cases and 3,530 (87%) controls participated. Mobile phone use increased the risk of glioma, OR = 1.3, 95% CI = 1.1-1.6 overall, increasing to OR = 3.0, 95% CI = 1.7-5.2 in the > 25 year latency group. Use of cordless phones increased the risk to OR = 1.4, 95% CI = 1.1-1.7, with highest risk in the >15-20 year latency group yielding OR = 1.7, 95% CI = 1.1-2.5. The OR increased statistically significant both per 100 h of cumulative use, and per year of latency for mobile and cordless phone use. Highest ORs overall were found for ipsilateral mobile or cordless phone use, OR = 1.8, 95% CI = 1.4-2.2 and OR = 1.7, 95% CI = 1.3-2.1, respectively. The highest risk was found for glioma in the temporal lobe. First use of mobile or cordless phone before the age of 20 gave higher OR for glioma than in later age groups.
The ipsilateral (same side of head where phone was used) relative risk of gloma for cell phone use increased from 1.8 (95% CI = 1.4-2.2) for more than 1 year of use to 4.6 (95% CI = 2.1-10.0) for more than 25 years of use (Table 5).
The contralateral (opposite side of head where phone was used) relative risk of gloma for cell phone use increased from 1.1 (95% CI = 0.8-1.4) for more than 1 year of use to 3.2 (95% CI = 1.2-8.6) for more than 25 years of use (Table 5).
Detailed information on materials and methods has been given previously ...For 1997-2003, cases and controls covered central Sweden , whereas the 2007-2009 study included the whole country  ...
Controls were ascertained from the Swedish Population Registry, covering the whole country and being continuously updated, such that each person was traced by a unique ID number. The registry also records the address to each person. For each case, one control subject of the same gender in the same 5-year group was drawn at random from this registry. They were assigned the same year for cut-off of all exposure as the diagnosis of the each case ...
Exposure was assessed using a mailed questionnaire sent to each person. Regarding use of a mobile phone, the time of average use (min per day) was estimated. The technology has changed since the first introduction of mobile phones. The first generation was analogue phones with an output power of 1 W at about 900 MHz followed by the 2nd generation GSM phones (2G) with either 900 or 1800 MHz frequency and with a pulsed output power. The mean output power was of the order of tens of mW. In the 3rd generation phones (3G) the output is more to be characterized as amplitude modulated than pulsed and the output power is of the order of tens of μW ...
Some special questions covered the extent of use in a car with an external antenna, and use of a hands-free device, both regarded as non- exposure to RF-EMF. The ear mostly used during phone calls, or equally both ears, was also noted.
Use of cordless desktop phones was covered by similar questions; years, average daily use, use of a hands-free device, and preferred ear. The procedure was conducted without knowledge of case/control status. Use of the wireless phone was referred to as ipsilateral (>50% of the time) or contralateral (<50 br="" in="" of="" relation="" side....="" the="" time="" to="" tumour="">
The questionnaire also contained a number of questions relating to the overall working history, exposure to different chemicals and other agents, smoking habits, X-ray investigations of the head and neck, and heredity traits for cancer ...
Adjustment was made for the matching variables gender, age (as a continuous variable) and year of diagnosis. It was also made for socio-economic index (SEI) divided into 4 categories ...
In total, 1,691 cases fulfilling the inclusion criteria were enrolled. Of these cases, 1,498 (89%) answered the questionnaire, of whom 879 were men and 619 women. The mean age was 52 (median 54, range 18-80) ...
Of the 4,038 controls, 3,530 (87%) participated, 1,492 men and 2,038 women. The mean age was 54 (median 55, range 19-80) ...
The median latency time for use of mobile phones in glioma cases was 9.0 years (mean 10.1, range 2-28). The corresponding results for cordless phones were median 7.0 years (mean 8.0, range 2-21) ... Analogue phones gave OR = 1.6, 95% CI = 1.2-2.0, increasing to OR = 4.8, 95% CI = 2.5-9.1 in the latency group of
>25 years. Note that the latency time was counted from the first use of the specific telephone type; for instance, a 2G digital phone user may have previously used an analogue phone.
Use of digital 2G phones gave overall OR = 1.3, 95% CI = 1.1-1.6 increasing to OR = 2.1, 95% CI = 1.5-3.0 with a latency >15-20 years, the longest latency interval. The results for digital 3G phones showed highest risk in the >5-10 years latency group, OR = 4.1, 95% CI = 1.3-12 ...
Digital type of mobile phones (2G, 3G) gave in total OR = 1.3, 95% CI = 1.1-1.6, increasing to OR = 2.1, 95% CI =1.5-3.0 in the longest latency group (>15-20 years).
Use of cordless phones gave OR = 1.4, 95% CI = 1.1-1.7, with highest risk in the latency group >15-20 years, OR = 1.7, 95% CI = 1.1-2.5 ...
The group of total wireless phone use (mobile phone and/or cordless phone) gave similar results to mobile phone use, with increasing risk with latency yielding highest risk in the longest latency group >25 years; OR = 3.0, 95% CI =1.7-5.2.
The risk increased per additional year of latency given for wireless phones; OR = 1.032, 95% CI = 1.019-1.046 ...
Wireless phone total use (>1,486 h) gave OR = 2.0, 95% CI = 1.6-2.6 in the 4th quartile, with similar results for total mobile and cordless phone use.
ORs increased statistically significant per 100 h of cumulative use for all types of phones (Table 3). Wireless phone increased the risk OR = 1.011, 95% CI = 1.008-1.014 per 100 h of cumulative use ...
The risks of glioma, based on different age groups for first use of wireless phones, are given in Table 8. Regarding mobile phone use, the highest OR was obtained for first use before the age of 20 years, OR = 1.8, 95% CI = 1.2-2.8. The risk increased for ipsilateral use to OR = 2.3, 95% CI = 1.3-4.2. Cordless phone gave OR = 2.3, 95% CI = 1.4-3.9 in total for the age group < 20 years, increasing to OR = 3.1, 95% CI = 1.6-6.3 for ipsilateral use.
Most of the types of malignant brain tumours were glioma (n = 1,380, 92.1%). The most malignant variety, astrocytoma grade IV (glioblastoma multiforme)
constituted 50.3% of the gliomas ... This study clearly shows an increased risk for glioma associated with use of both mobile and cordless phones, a risk that increased significantly with latency and cumulative use. The highest risk was in the longest latency group (> 25 years), giving a statistically significant 3-fold increased risk. Overall a high risk was found for use of the third generation (3G) mobile phones, with OR=4.1, 95% CI = 1.3-12 in the latency group >5-10 years. The risk increased with 4.7% per 100 h cumulative use and with 15.7% per year of latency.
Children and adolescents are more exposed to RF-EMF than adults due to thinner skull bone, higher conductivity in the brain tissue, and a smaller head. Also the developing brain is more vulnerable than in adults and it is still developing until about 20 years of age . We analysed glioma risk in different age groups for first use of a wireless phone. Regarding both mobile and cordless phones OR was highest among subjects with first use before 20 years of age. The risk increased further for ipsilateral use to OR = 2.3, 95% CI = 1.3-4.2 for mobile phone use and to OR = 3.1, 95% CI = 1.6-6.3 for cordless phone use. These results are
consistent with our previous findings [8,15,29,30].
One strength of our study was the high percentage of participating cases and controls, 86% and 87%, respectively, making it unlikely that selection bias influenced the results ...
Recall bias might have been an issue, such that cases would have overestimated their use of wireless phones. To address this point, we used meningioma cases from the same study as the reference entity in one analysis, which showed an increased risk of glioma with wireless phone use. Thus it is unlikely that our present results using population-based controls are explained by recall bias.
In analysis of survival of glioma cases in our previous studies [13,15,25], we found generally a decreased survival of glioma cases with long-term and high cumulative use of wireless phones ; this indicates a complex biological effect from RF-EMF exposure and strengthens a causal association between glioma and the use of wireless phones.
Conclusion. We previously analysed the evidence on glioma associated with the use of wireless phones using the Hill criteria . We concluded that glioma and also acoustic neuroma are caused by RF-EMF emissions from wireless phones, and thus regarded as carcinogenic, under Group 1 according to the IARC classification, indicating that current guidelines for exposure should be urgently revised. This pooled analysis gives further support to that conclusion regarding glioma.
Joel M. Moskowitz, Ph.D.
Director, Center for Family and Community Health
School of Public Health, University of California, Berkeley
Electromagnetic Radiation Safety
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