A major study of 358,403 mobile phone users in Denmark has found no link between long-term cell phone use and tumors. Previous studies about mobile phone use and tumors have so far been inconclusive, especially as far as long-term use of phones. The new Danish study, just published in the the British Medical Journal, disputes what a World Health Organization panel since just five months ago, that cellphones are “possibly carcinogenic.” But another study carried out in 13 countries found no overall increased risk linking cell phone use to cancer, but did say that that those with the highest level of cellphone use had a 40 percent higher risk of glioma, an aggressive type of brain tumor.
In the new Danish study, researchers led by the Institute of Cancer Epidemiology in Copenhagen looked at data for the whole Danish population aged 30 and over and born in Denmark after 1925, dividing people into subscribers and non-subscribers of mobile phones before 1995.
Overall, 10,729 central nervous system tumours occurred in the study period 1990-2007.
When the figures were restricted to people with the longest mobile phone use — 13 years or more — cancer rates were almost the same in both long-term users and non-subscribers of mobile phones.
Researchers emphasized that a “small to moderate increase in risk for subgroups of heavy users or after even longer induction periods than 10-15 years” still needs to be considered and have called for more research of large study populations.
Tara Parker-Pope of the New York Times notes the strengths of this study as well as a weakness:
The Danish study is important because it matches data from a national cancer registry with mobile phone contracts beginning in 1982, the year the phones were introduced in Denmark, until 1995. Because it used a computerized cohort that was tracked through registries and digitized subscriber data, it avoided the need to contact individuals and thus eliminated problems related to selection and recall bias common in other studies.
However, the major weakness of the study is that it counted cellphone subscriptions rather than actual use by individuals, and failed to count people who had corporate subscriptions or who used cellphones without a long-term contract. Those small details could have diluted any association between cellphone use and cancer risk, the investigators conceded.
With more than five billion mobile phone subscribers worldwide in 2010, concerns about health effects, and especially about tumors in the central nervous system, have risen accordingly. Scientists describe the results of the new study as “reassuring.” Even if consumers do not find them to be such, are we any more likely to start using our cell phones less?
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