Tuesday, November 11, 2014

Are wireless phones linked with brain cancer risk?

Are wireless phones linked with brain cancer risk?

Ronnie Cohen, Reuters Health, Nov 11, 2014

(Reuters Health) - Swedes who talked on mobile or cordless phones for more than 25 years had triple the risk of a certain kind of brain cancer compared to those who used wireless phones for less than a year, a new study suggests.

The odds of developing glioma, an often deadly brain cancer, rose with years and hours of use, researchers reported in the journal Pathophysiology. 

“The risk is three times higher after 25 years of use. We can see this clearly,” lead researcher Dr. Lennart Hardell told Reuters Health in a telephone interview.

His finding contrasts with the largest-ever study on the topic - the international Interphone study, which was conducted by the International Agency for Research on Cancer and funded in part by cell phone companies. That study, published in 2010, failed to find strong evidence that mobile phones increased the risk of brain tumors.

Even if the odds of developing a glioma were doubled or tripled, however, the risk would still remain low.

A little more than 5 out of 100,000 Europeans (or 0.005 percent) were diagnosed with any kind of malignant brain tumor between 1995 and 2002, according to a 2012 study in the European Journal of Cancer (bit.ly/1xIlQam). If the rate triples, the odds rise to about 16 out of 100,000 (or 0.016 percent).

Hardell, an oncologist from University Hospital in Orebro, Sweden, and his colleague Michael Carlberg matched 1,380 patients with malignant brain tumors to people without such tumors and compared their wireless phone use.

People who reported using wireless phones for 20 to 25 years were nearly twice as likely to be diagnosed with glioma as those who reported using them for less than a year, the study found. Those who used cell and cordless phones for more than 25 years were three times more likely to develop one of these tumors. 

The study did not show an association of wireless phones with malignant brain tumors other than glioma.

Participants who recalled talking the most – more than 1,486 hours – on wireless phones were twice as likely to develop glioma compared to those who said they used the devices the fewest hours – between one and 122 hours, the study found.
Case control studies such as this suffer from a number of limitations, however, the most serious being the need for participants to remember their behavior patterns from decades earlier. 
Dr. Gabriel Zada, a neurosurgeon at the University of Southern California’s Keck School of Medicine, who wasn’t involved in Hardell’s study, advises precautionary measures, such as using the phone’s speaker or a hands-free headset. 

But he told Reuters Health the new study failed to answer his patients’ questions about why they developed brain tumors.

“A lot of people ask me, ‘Why did I get this brain tumor?’” he said. “There are a lot of different theories. It’s a much more convoluted picture than just saying cell phones caused this.”

In a 2012 study, Zada reported that rates of malignant tumors in parts of the brain closest to where people hold their phones rose significantly in California from 1992 to 2006 – although the incidence of gliomas throughout the brain decreased (1.usa.gov/1tZffI2).
U.S. cell phone use tripled between 2000 and 2010, according to CTIA - the Wireless Association, which represents manufacturers. But in the U.S. overall, rates of cancer in parts of the brain that would be more highly exposed to radio frequency radiation from cell phones had not gone up at the time of a 2010 report in the journal Neuro-Oncology (bit.ly/10W3F6z). 

Zada believes the current study underscores the need for more research. 

“It is more evidence suggesting a possible association between brain tumors and cell phones,” he said. “But it’s certainly not convincing that cell phones cause brain cancer.”
A World Health Organization panel of 31 scientists from 14 countries classified mobile phones as “possibly carcinogenic” in 2011. The U.S. Federal Communications Commission is currently reassessing the safe radiation exposure limits it adopted in 1996.

Cell phones emit radiofrequency energy, which can be absorbed by tissues closest to where the phone is held, the National Cancer Institute says on its website. “Studies thus far have not shown a consistent link between cell phone use and cancers of the brain, nerves, or other tissues of the head or neck,” it says. 

Hardell is one of the few researchers who include cordless phones when studying cell phones and cancer risk. He believes emissions from the base stations of cordless phones can be problematic, especially when users sleep next to them.

Children may be most vulnerable to wireless phone emissions, Hardell said. They absorb more radio frequency electromagnetic fields, he writes, because of their small heads, thinner skulls and higher brain conductivity.

“Girls tends to put the smart phone below the pillow,” he said. “It’s a bad habit to go to bed with your smart phone.”

Zada also believes developing brains may be more susceptible and recommends against sleeping with cell phones. 

Nevertheless, he said: “It’s hard to make formal recommendations because the data is lacking. It’s not smoking and lung cancer because it’s not proven.”

SOURCE: bit.ly/1xGCOpu Pathophysiology, online October 28, 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:

Cell and cordless phone risk for glioma - Analysis of pooled case-control studies in Sweden, 1997-2003 and 2007-2009

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.pathophys.2014.10.001


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.


Key Findings

The relative risk of glioma for wireless (cell and cordless) phone use increased from 1.3 (95% CI = 1.1-1.6) for more than 1 year of use to 3.0 (95% CI = 1.7-5.2) for more than 25 years of use (Table 2).

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).
The overall relative risk of glioma for 1-122 hours of wireless phone use was 1.2 (95% CI = 0.9-1.4) whereas the risk for more than 1,486 hours was 2.0 (95% CI = 1.6-2.6) (Table 6).
The ipsilateral relative risk of glioma for people who first used mobile phones  at less than 20 years of age was 2.3 (95% CI =1.3-4.2) whereas the risk for those who first used mobile phones at 50 years of age or older was 1.7 (95% CI =1.3-2.2) (Table 8).


Detailed information on materials and methods has been given previously ...For 1997-2003, cases and controls covered central Sweden [13], whereas the 2007-2009 study included the whole country [24] ...

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 digital type of wireless phones (2G, 3G and/or cordless phone) gave OR = 1.3, 95% CI = 1.1-1.6, increasing to OR = 1.6, 95% CI = 1.3-2.0 in the latency group >5-10 years, then tending to drop, and again increasing to OR = 2.0, 95% CI = 1.5-2.8 risk in the latency group >15-20 years.

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 [31]. 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.
Of certain interest is the higher risk we observed for 3G mobile phone use compared with other types. However, this observation was based on short latency and rather low numbers of exposed subjects. Contrary to 2G GSM, 3G universal global telecommunications system (UMTS) mobile phones emit wide-band microwave (MW) signals. Hypothetically, UMTS MWs may result in higher biological effects compared to GSM signal because of eventual "effective" frequencies within the wideband [32,33]. To our knowledge, there are only two mechanistic studies, which compare effects of 2G and 3G signals using the same experimental approach under well-defined conditions of exposure [32,34] ...

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 [36]; 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 [20]. 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
Center: http://cfch.berkeley.edu

Electromagnetic Radiation Safety

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