diciembre 2000

Do teenagers with mobile phones smoke less?

The media showed interest in a report that a recent decline in teenage smoking in the UK could be due to an increase in ownership of mobile phones. In a letter to the British Medical Journal, Drs. Charlton and Bates argue " that the mobile phone is an effective competitor to cigarettes in the market for products that offer teenagers adult style, individuality, sociability, rebellion, peer group bonding, and adult aspiration."

There were a number of email responses to the journal. Several correspondents pointed out that a similar trend has not been seen in other countries such as Italy, Australia, and Switzerland.

It should be pointed out that in an ecological study such as this a causal relationship should not be assumed. There are probably many other factors that play a part in the reported trends.

Reference: Charlton A, Bates C. Decline in teenage smoking with rise in mobile phone ownership: hypothesis. BMJ 2000;321:1155.

Do cell phone users get more headaches than non-users?

Another letter in the same issue of the British Medical Journal reported a study on cell phone users in Singapore. Headaches were thirty per cent more likely in cell phone users than in those who did not use a cell phone.

The authors published an article on the same study in the November 2000 issue of Environmental Health Perspectives. They point out that the use of cellular phones was not associated with a significant increase of central nervous system symptoms other than headaches.

This was a cross-sectional study, which is a weak type of study to try to prove a causal relationship, primarily because the temporal relationship of the exposure and the outcome is obscured. Clearly, many factors could affect the response seen in this paper, including personal characteristics and predisposing medical conditions of the subjects.

References: Chia S-E, Chia H-P, Tan J-S, Vlassov V. Health hazards of mobile phones. BMJ 2000;321:1155
Chia S-E, Chia H-P, Tan J-S. Prevalence of headaches among handheld cellular telephone users in Singapore: A community study. Environmental Health Perspectives 2000;108:1059-1062.

Lancet seminars examine safety of mobile phones

In a recent issue of the Lancet, a British medical publication, two papers discussed the safety of mobile phones. Dr G. Hyland reviewed the physics and biology of mobile telephony. He argues that low intensity, pulsed radiation used in mobile phones and their base stations can exert subtle, non-thermal influences on living organisms. He argues that these may arise because of a synergy between the frequencies generated by the phone and electrical activities of the organism. Hyland further suggests that living organisms may react not only to the frequency of the microwave carrier but also to the lower frequency pulsings, at 2 Hz and 8.34 Hz, which are features of some systems such as the TDMA system.

In the second paper Dr K. Rothman discusses epidemiological evidence on health risks. He states that there is no clear evidence of an association with brain tumours or other malignancies but points out that there have been few studies of the effects of radiofrequency exposure. At present, he says, "the main public-health concern is clearly motor vehicle collisions, a behavioural effect rather than an effect of radiofrequency exposures as such."

Dendy points out in an accompanying commentary that there are problems with the evidence that Hyland cites in his paper. These include the lack of reproducibility, and the absence of either a direct quantitative link between cause and effect or a proven causative mechanism.

References: Dendy PP. Mobile phones and the illusory pursuit of safety. Lancet 2000;366:1782-1783.
Hyland GJ. Physics and biology of mobile telephony. Lancet 2000;356:1833-1836.
Rothman KJ. Epidemiological evidence on health risks of cellular telephones. Lancet 2000;356:1837-1840.

Current research on cell phones and cancer

Rothman, in the paper discussed above, also discusses ongoing research that is studying the relationship between cell phones and cancer. One study, coordinated by the National Cancer Institute in the US, is expected to report its findings next year. PD Inskip and colleagues reported the design of this study in an article in Radiation Protection Dosimetry last year.

Another recent article in Epidemiology reviews the discussion that took place at an International Workshop last year on the relation between mobile telephones and tumours of the brain, head, and neck. Various current research studies are mentioned. For further information on this see "What's New Archives, April 2000 and November 1999.

References: Inskip PD, Hatch EE, Stewart PA, et al. Study design for a case-control investigation of cellular telephones and other risk factors for brain tumours in adults. Radiation Protection Dosimetry 1999;86:45-52.

Blettner M, Michaelis J, Wahrendorf J. Workshop on research into the health effects of cellular telephones. Epidemiology 2000;11:609-611.

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