From Medscape Education Clinical Briefs
07/29/2011;
Clinical Context
The possibility of a higher risk for brain tumors related to the use of mobile phones is truly frightening, particularly if such a risk applies to children and adolescents as well as to adults.The current study by Röösli and colleagues provides some background regarding whether an association between mobile phone use and the incidence of brain tumors in young people is possible.
Children's developing nervous systems may indeed be more vulnerable to radiofrequency electromagnetic fields associated with mobile phones.
However, the radiofrequency radiation emitted by mobile phones is insufficient to damage DNA directly, and it is nonionizing.
Animal models have not found mobile phone radiation to be carcinogenic, and epidemiologic research has generally not demonstrated significant trends toward a higher prevalence of brain tumors among children since the introduction of the mobile phone.
Nonetheless, children and parents might remain concerned regarding the potential risks of mobile phone use. The current study evaluates how these devices affect the risk for brain tumors in a cohort including hundreds of children and adolescents.
Study Synopsis and Perspective
A new study has found that children and adolescents who use cell phones do not appear to be at a higher risk for brain cancer, adding to the ongoing debate about the possible association between cell phone use and brain tumors.The study, conducted by Martin Röösli, PhD, senior investigator at Swiss Tropical and Public Health Institute in Basel, Switzerland, and colleagues, looked at children and adolescents who were diagnosed with a brain tumor. The team found that patients with tumors were not statistically significantly more likely to have been regular cell phone users than control subjects.
This study, published online July 27 in the Journal of The National Cancer Institute, is the first to specifically assess the health impact of cell phone use on children and adolescents.
Even though evidence that children are more sensitive to nonionizing radio waves than adults is lacking, "there is genuine concern for the obvious reasons that children are young, growing, and have many years of life remaining," the authors of an accompanying editorial write.
However, the study is consistent with virtually all studies of adults exposed to radiofrequency waves, and "no convincing evidence was found that children who use cell phones are at higher risk of developing a brain tumor than children who do not regularly use cell phones," note John D. Boice, Jr, ScD, and Robert E. Tarone, PhD, from the International Epidemiology Institute in Rockville, Maryland, and Vanderbilt University in Nashville, Tennessee.
But even though the study has filled a gap in our knowledge by showing that there is no increased risk for brain tumors in children and adolescents who are regular cell phone users, the editorialists point out that "it is impossible to prove a noneffect, and it will be debated whether and at what level additional research funds should be spent in assessing health effects associated with nonionizing radiation, especially in times of limited resources."
Research is ongoing, and includes a prospective study that is recruiting 250,000 cell phone users in 5 European countries, and a case–control study of 2000 young people, between 10 and 24 years of age, who were diagnosed with a brain tumor and 2000 control subjects from 13 countries. In the meantime, Drs. Boice and Tarone concur with the study authors that the incidence rates of brain cancer in the general population should continue to be monitored, and that individuals who are concerned should consider alternatives to holding a cell phone up to their ears (such as an ear piece or the speaker option).
When considering the need for future health research on cell phones, Drs. Boice and Tarone note that "in addition to the negative epidemiological data, there is no known biologically plausible mechanism by which nonionizing radio waves of low energy can disrupt DNA and lead to cancer."
Rise in Use and Debate Reignited
Over the past several years, a number of studies have attempted to examine the association between cell phone use and an increased risk for brain tumors. To date, the evidence has been inconclusive, although some countries have begun to take precautionary measures.
The debate was reignited in May, when the World Health Organization announced that radiofrequency electromagnetic fields have been classified as possibly carcinogenic to humans (group 2B) on the basis of an increased risk for glioma that some studies have associated with the use of wireless phones.
There has been a dramatic rise in the use of cell phones by children and adolescents during the past few years, and it has been hypothesized that they might be more vulnerable than adults to the possible detrimental health effects of cell phone exposure.
No Increase in Tumors
Dr. Röösli and colleagues, conducted an international case–control study of the relation between cell phone use and the risk of developing brain tumors in children and adolescents. The 352 participants were 7 to 19 years of age, resided in Denmark, Sweden, Norway, or Switzerland, and were diagnosed with a brain tumor from 2004 to 2008. The control group consisted of 646 age-, sex-, and region-matched children.
Of the patients with brain tumors, 162 (46.0%) were diagnosed with an astrocytoma, 21 (6.0%) with ependymoma, 30 (8.5%) with another glioma, 62 (17.6%) with primitive neuroectodermal tumors, 53 (15.1%) with other specified intracranial neoplasms, and 24 (6.8%) with unspecified intracranial neoplasms.
Cell phone use was determined from interviews and phone-network providers, if the information was available.
A similar percentage of subjects in the case and control groups reported having spoken on a cell phone more than 20 times before the case patient was diagnosed (75.3% vs 72.1%). Furthermore, 55% of the case group and 51% of the control group reported regularly using a cell phone.
The authors found that children who had used cell phones for at least 5 years were not at higher risk than those who had never regularly used cell phones (odds ratio [OR], 1.26). There was also no increased risk for brain tumors in the areas of the brain with the highest exposure to radiofrequency, such as the temporal and frontal lobes and the cerebellum. Interestingly, in regular users, the odds ratio for tumors in the parts of the brain with the lowest exposure to radiation was statistically significant (OR, 1.92).
Possible Risk?
Information on first subscription activations was available for 35% of case patients and 34% of control subjects. There was a statistically significantly increased risk for the 24 case patients and 25 control subjects who had provider-verified cell-phone subscriptions for more than 2.8 years (OR, 2.15; P trend < .001).
The relations between brain tumor risk and cumulative duration of subscription, cumulative hours of use, and cumulative number of calls were not statistically significant.
"The lack of an exposure–response relationship, given our finding that risk was related to neither the amount of [cell] phone use nor the location of the tumor, does not support a causal interpretation," the authors write.
However, they add that the possibility that cell phones might confer a small increase in risk cannot be ruled out. Therefore, they emphasize "the importance of future studies with objective exposure assessment or the use of prospectively collected exposure data."
J Natl Cancer Inst. Published online July 27, 2011.
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