BMJ: Another Reassuring Report On Cell Phones & Brain Cancer

 

# 5914

 

Yesterday, the British Medical Journal published the results of a follow up to large Danish cohort study that found no link between cell phone usage and an increase in brain tumors.

 

Although evidence for it has been scant, for a number of years some scientists have expressed concerns that prolonged exposure to cell phone RF (radio frequency) electromagnetic fields might cause certain types of head and neck cancers.

 

In 2010, the International Agency for Research on Cancer (IARC) released their long-delayed INTERPHONE report, which was unable to establish a link between cell phone use and brain tumors  (see The IARC Cell Phone Report).

 

Despite that initial finding, a year later (May 2011) the IARC released a statement (IARC Press Release N° 208) that listed mobile phone use in same `possibly’ carcinogenic hazard category as exposure to gasoline, engine exhaust and lead.

 

For details on this statement, you may wish to revisit IARC: Cell Phones `Possibly Carcinogenic’.

 

A couple of months later we saw a study that appeared in the Journal of the National Cancer Institute (see Reassuring Study On Cell Phones & Brain Cancer Risks) that found no link between cell phone use and brain tumors in children and adolescents.

 

While it is unlikely to be the final word on the subject, the study published yesterday in the BMJ follows up on the largest cohort study on mobile phone users to date.

 

And once again, the news is reassuring; long-term subscribers to cellular phone services showed no increase in brain or central nervous system tumors over non-subscribers. 

 

 

Use of mobile phones and risk of brain tumours: update of Danish cohort study

OPEN ACCESS

BMJ 2011; 343:d6387

Patrizia Frei, Aslak H Poulsen, Christoffer Johansen,  Jørgen H Olsen, Marianne Steding-Jessen,  Joachim Schüz

ABSTRACT

Participants All Danes aged ≥30 and born in Denmark after 1925, subdivided into subscribers and non-subscribers of mobile phones before 1995.

 

Main outcome measures Risk of tumours of the central nervous system, identified from the complete Danish Cancer Register. Sex specific incidence rate ratios estimated with log linear Poisson regression models adjusted for age, calendar period, education, and disposable income.

 

Results 358 403 subscription holders accrued 3.8 million person years. In the follow-up period 1990-2007, there were 10 729 cases of tumours of the central nervous system. The risk of such tumours was close to unity for both men and women. When restricted to individuals with the longest mobile phone use—that is, ≥13 years of subscription—the incidence rate ratio was 1.03 (95% confidence interval 0.83 to 1.27) in men and 0.91 (0.41 to 2.04) in women. Among those with subscriptions of ≥10 years, ratios were 1.04 (0.85 to 1.26) in men and 1.04 (0.56 to 1.95) in women for glioma and 0.90 (0.57 to 1.42) in men and 0.93 (0.46 to 1.87) in women for meningioma. There was no indication of dose-response relation either by years since first subscription for a mobile phone or by anatomical location of the tumour—that is, in regions of the brain closest to where the handset is usually held to the head.

 

Conclusions In this update of a large nationwide cohort study of mobile phone use, there were no increased risks of tumours of the central nervous system, providing little evidence for a causal association.

 

 

While this study was subject (as are all studies) to some limitations, In an accompanying BMJ editorial (Mobile telephones and brain tumours) professors Anders Ahlbom and Maria Feychting called the evidence in this report `reassuring’.

 

They cautioned, however, that `continued monitoring of health registers and prospective cohorts is still warranted.’

Reassuring Study On Cell Phones & Brain Cancer Risks

 

 

Photo Credit – Wikipedia

 

# 5822

 

Two months ago the World Health Organization’s International Agency for Research on Cancer (IARC) issued a new statement (IARC Press Release N° 208) that lists mobile phone use in same carcinogenic hazard category as exposure to gasoline, engine exhaust and lead.

 

For details on this announcement, you may wish to revisit IARC: Cell Phones `Possibly Carcinogenic’.

 

For a number of years some scientists had expressed concerns that prolonged exposure to cell phone RF (radiofrequency) electromagnetic fields might cause certain types of head and neck cancers.

 

And many researchers worried that children, teenagers, and young adults - who rank among the most fervent users of cell phones - could be at particular risk.

 

While it probably won’t settle the debate, today we’ve a new study that appears in the Journal of the National Cancer Institute that reassuringly found no link between cell phone use and brain tumors in children and adolescents.

 

 

Mobile Phone Use and Brain Tumors in Children and Adolescents: A Multicenter Case–Control Study

Denis Aydin, Maria Feychting, Joachim Schüz, Tore Tynes, Tina Veje Andersen, Lisbeth Samsø Schmidt, Aslak Harbo Poulsen, Christoffer Johansen, Michaela Prochazka, Birgitta Lannering, Lars Klæboe, Tone Eggen, Daniela Jenni, Michael Grotzer, Nicolas Von der Weid, Claudia E. Kuehni and Martin Röösli

 

The authors examined the medical records of 352 children aged 7-19  from Norway, Denmark, Sweden, & Switzerland with brain tumors. They conducted interviews with them to determine their cell phone usage, and compared this data to 646 control subjects.

 

The researchers found no statistically significant increase in the incidence of brain tumors among children and adolescents who were exposed to cell phone radiation, compared to those who were not.

 

Their conclusion:

 

The absence of an exposure–response relationship either in terms of the amount of mobile phone use or by localization of the brain tumor argues against a causal association.

 

 

Today’s study has some limitations. 

 

It is based primarily on self-reported data, the subjects had been using cell phones for an average of only 4 years, and much of this usage was likely text messaging -as opposed to voice calls – which would reduce radiation exposure to the head and neck.

 

Since it can take years – or even decades – for brain cancers to develop, the true health impacts from the stratospheric rise in cell phone use over the past decade may be difficult to accurately gauge for some time.

 

While today’s results are encouraging, the authors believe that it is important to continue to study the issue and be on the lookout for potential negative health effects related to cell phone use in children.

IARC: Cell Phones `Possibly Carcinogenic’

 

 

# 5588

 

 

It was just over a year ago that the the World Health Organization’s International Agency for Research on Cancer (IARC) released their long-delayed INTERPHONE report, which was unable to establish a link between cell phone use and brain tumors (see The IARC Cell Phone Report) .

 

For a number of years some scientists have expressed concerns that prolonged exposure to cell phone RF (radiofrequency) electromagnetic fields might cause certain types of head and neck cancers.

 

And researchers worried that children, teenagers, and young adults, who rank among the most fervent users of cell phones, could be at particular risk.

 

While reassuring, the 2010 INTERPHONE report wasn’t exactly an `All Clear’ on cell phone dangers. The study, the authors admitted, had limitations. And some scientists were less than mollified by their findings.

 

At the time, Dr Christopher Wild, Director of IARC warned that additional studies were warranted.  From the IARC press release of May, 2010:

 

"An increased risk of brain cancer is not established from the data from Interphone.

 

However, observations at the highest level of cumulative call time and the changing patterns of mobile phone use since the period studied by Interphone, particularly in young people, mean that further investigation of mobile phone use and brain cancer risk is merited."

 

Earlier this year we also saw a major report in the Journal of the American Medical Association that looked at the effects of RF signal exposure on brain activity (see JAMA: Cell Phone Use Stimulates Brain Activity).

 

Using PET scans researchers were able to prove that areas of the brain in close proximity to the antennas of activated cell phones demonstrated increased glucose uptake, indicating increased localized brain activity in response to the RF (radio frequency) emissions.

 

This study indicates that the prolonged use of a cell phone does affect brain activity. What all this might mean in regards to human health remains unknown for now.

 

Fast forward to today, and the IARC has released a new statement (IARC Press Release N° 208) that lists mobile phone use in same carcinogenic hazard category as exposure to gasoline, engine exhaust and lead.

 

 

 

Given the popularity of (and our societal reliance upon) cell phones, this report – which classifies radio-frequency electromagnetic fields as possibly carcinogenic to humans (Group 2B) - is likely to spur a good deal of news coverage.

 

Group 1 carcinogens are those that are most strongly associated with cancer, like smoking and asbestos, and are considered the most dangerous.

 

Group 2a carcinogens are considered probably carcinogenic based on limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals.

 

Group 2b carcinogens – where cell phones have now been ranked – are considered possibly carcinogenic, but evidence is limited in both humans and experimental animals.

 

For now, the evidence supporting a link between cell phones and certain types of brain cancer is limited. However, Dr Jonathan Samet, the overall chairman of the working group  states :

 

“ . . . the  evidence, while still accumulating, is  strong enough to support a conclusion and the 2B classification. The conclusion means that there could be some risk, and therefore we need to keep a close watch for a link between cell phones and cancer risk.” 

 

 

None of this proves that cell phones cause brain cancer.  Only that there is enough evidence to suggest a link to a specific type of cancer (glioma), and that more studies must be done.

 

Since it can take years – or even decades – for brain cancers to develop, the true health impacts from the stratospheric rise in cell phone use over the past decade may be difficult to accurately gauge for some time.

 

A full report on the IARC’s findings will be published over the next few days in The Lancet Oncology.