MTHR - Mobile Telecommunications and Health Research

Epidemiology Workshop

Chair: Professor C Chilvers

Researchers representing all the epidemiological studies funded by the MTHR programme spoke on progress made during the last year. All the researchers were undertaking either case-control or cohort studies. A case-control study involves identifying people suffering from a particular disease, the case, and matching them with a control, i.e. a person with a similar background and lifestyle, who is not suffering from that disease. The study examines whether there is a relationship between exposure to a particular agent and incidence of the disease. For the MTHR projects the agent is the radiofrequency signal emitted by a mobile phone or base station. Exposure assessment can only be carried out retrospectively. A cohort study identifies a group of people, for example people who live in the same area or have a similar job. The health of the subjects is then monitored and any relationship between exposure to a particular agent and incidence of various diseases can then be evaluated. These studies have the advantage that a number of diseases can be investigated simultaneously and they offer potential for accurate exposure assessment.

Several common themes were explored. Particular issues discussed included difficulties associated with recruitment of matched controls for the cases in the case control studies. The researchers noted that this was a problem for epidemiologists internationally. Several options for control recruitment were explored. It was noted that since the implementation of the data protection act community based controls, who would be contacted through the local GP or via the electoral roll, had become increasingly difficult to contact. Hospital based controls, that is people who could be identified as suitable controls when admitted to a hospital, were considered unsuitable for these studies as the condition requiring hospital admission may add bias to the study. It was suggested that relatives of the case could be suitable and highly motivated controls.

The importance of highly trained research nurses to perform interviews for the case-control studies was explored. It was noted that the research nurse could not be blinded to the case or control status of the interviewee (i.e. whether the interviewee was ill or not). It was agreed that training of research nurses was critical to eliciting accurate details of exposure to radiofrequency signals. As well as ensuring that the research nurses were sufficiently trained it was noted that highly structured interview formats pre-defined by computer assisted interview programmes were being used in some of the projects to minimise any bias in the interview process.

The challenges associated with the exposure of individuals to radiofrequency signals were considered. For studies assessing exposure to mobile phone base stations methods of modelling the exposure at a particular location were discussed. In addition, the importance of validation studies for these modelled exposures was recognised. For studies that need to assess exposure from mobile phones the inaccuracy in self reporting of mobile phone use, other methods for collecting information on mobile phones use and the importance of being aware of the make and model of mobile phone used was discussed.

Summaries of the closed sessions of the MTHR Research Seminar - 4th of November 2003