Epidemiology

Extended Follow-Up of the Danish Cohort of Mobile Phone Subscribers

To extend the follow up period of a retrospective cohort study on mobile phone subscribers in Denmark and occurrence of cancer, with regard to longer latency periods. Also to use this cohort for investigating the risk of CNS diseases among this cohort.

During the late 1990s the Institute of Cancer Epidemiology at the Danish Cancer Society (DCS) conducted a retrospective cohort study of cancer incidence in Denmark among mobile phone subscribers in the period 1982 (the year of the introduction of this technology in Denmark) and 1995. Subscriber lists from the two operating companies in the country identified 420,095 cellular telephone users. All cohort members are linked to the CPR (Central Population Registery) for information on vital status, and to the files of the Cancer Registry and of the Danish National Register of Patients.

Exposure is defined by subscriber status from network operator data. From the information on years since first subscription, years of exposure can be calculated.

The paper on the follow up for cancer was published in December 2006 in the Journal of the National Cancer Institute. A letter to the Journal and our reply was published in the April 18 issue of the Journal of the National Cancer Institute. Additional analyses on how the potential of exposure misclassification in the subscriber cohort could affect the risk estimation have been published in the February 2007 issue of Bioelectromagnetics.

A total of 14 249 cancers were observed in the cohort (relative risk estimate (SIR) 0.95; 95% confidence interval [CI]= 0.93 to 0.97) for men and women combined. No increases in SIR were found for brain tumors (SIR 0.97), acoustic neuromas (SIR 0.73), salivary gland tumors (SIR 0.77), eye tumors (SIR 0.96) or leukemias (SIR 1.00). The SIR for brain tumors in long-term subscribers of 10 years was decreased but there was no trend with time since first subscription. Additional data on income and smoking prevalence, primarily among men indicated that early cellular telephone subscribers had a higher income and a healthier life-style. A comparison between subscriber data and self-reported cellular telephone use showed fair agreement. The study provides no evidence for an association between tumor risk and cellular telephone use among either short-term or long-term users. For long-term users, however, numbers were still small and as no distinction between heavy and light users was possible, further studies are needed.

Study team: Joachim Schüz, Jørgen H Olsen, Rune Jacobsen, Christoffer Johansen/PI (Danish Cancer Society), John D Boice Jr, Joseph K McLaughlin (USA)

Cefalo (An international case-control study on childhood brain tumors)
Denmark, Norway, Sweden, Switzerland

The main hypothesis of the study is to investigate whether the use of mobile telephones increases the risk of developing brain tumours in children and adolescents in the age group 7-19 years.

The design of the study is a population-based case-control study. The case group comprises primary brain tumour cases in the respective age group who were diagnosed in the period spring 2005 until spring 2008. Population-based controls are randomly selected from population registries to compile the comparison group (2 controls per case). The completeness of case ascertainment in each country is secured by close collaborations with the respective clinical departments and the use of various national population-based registries, i.e. cancer registries, pathology registries, and national registries of patients. Clearance from the respective physicians will be obtained before contacting the affected families. For the whole study period, a total of 555 eligible cases are expected in the four participating countries.

In a first step, a face-to-face interview on mobile phone use is conducted with both the child and one of the parents. In addition to questions on mobile phone use, the questionnaire comprises questions on potential confounding factors. In a second step, downloads of traffic data of mobile phone use for the most recent years will be provided from the network operators, to validate the recent use of mobile phones given during the interview.

The field work has started in mid 2006. The UK has just joined the group and starts with a feasibility study.

Project team: Joachim Schüz/PI, Lisbeth Samsø Schmidt, Lissa Churchward, Christoffer Johansen, Jørgen H Olsen (Danish Cancer Society), Maria Feychting (PI/Sweden), Lars Klaeboe (PI/Norway), Martin Röösli (PI/Switzerland), Patricia McKinney (PI/UK)

Cosmos (International Cohort Study of Mobile Phone Use and Health)
Denmark, Sweden, United Kingdom (UK), Finland, Netherlands

The main hypothesis of the study is to investigate whether use of mobile telephones has adverse health effects. The study is specifically designed to examine possible small risks after long induction periods.

The design of the study is a prospective cohort study with an internal comparison of exposure groups. The study will be carried out as a collaborative study, comprising up to 250,000 mobile phone users in up to five countries, according a joint study protocol. The cohort comprises a sample of mobile phone users recruited from subscriber lists from network operators, with an effort to have a large group of heavy mobile phone users in the cohort.

Exposure is assessed by a self-administered questionnaire, with questions on current mobile phone use, start of mobile phone use, and various lifestyle factors that are potential confounders in the evaluation of the risk of a variety of endpoints. For a subsample of subjects, traffic records are downloaded from network operators to evaluate agreement between records and self-reported data. Due to the expected changes in technology and mobile phone use patterns, exposure assessment by questionnaire will be repeated about every four years.

The endpoints of the study are incidence and mortality of several cancers, neurodegenerative diseases, cerebrovascular diseases, and health symptoms, like headache, sleep disorders, or general well-being. The follow up on disease endpoints will be done by linking the cohort with cancer registries, national registries of patients, and mortality registries. Changes in symptoms will be assessed by having questions on the baseline and the repeated questionnaires. Only validated instruments to assess symptoms will be applied.

The launch of the study is planned for autumn 2007 in Denmark and spring next year in Sweden and in the UK. In Finland and the Netherlands the decision about joining Cosmos is still pending.

Project team: Joachim Schüz/PI, Aslak Harbo Poulsen, Lissa Churchward, Christoffer Johansen, Jørgen H Olsen (Danish Cancer Society), Anders Ahlbom (PI/Sweden), Paul Elliott (PI/UK), Anssi Auvinen (PI/Finland), to be determined (Netherlands)

Read abstract from this study here ...

Mobile telephone in Denmark: use and risk perception – a qualitative approach

Study objectives
The Danish mobile phone risk study addresses the specific concerns in relation to mobile phones, the relative strengths of these concerns and how widespread they are in the population. The qualitative study presented here, focuses on understanding of and trust in information on risks associated with radiation from mobile phones and base stations and how it is influenced by the information format and source. The findings have been used in development of a questionnaire used on a larger scale covering a representative stratum of the Danish population.

Study design
This study was based on semi-structured qualitative interviews with 20 families. These families represented four different situations. One group lived in a geographic area with no mobile phone base station implemented or presently planned, one group lived in an area with a base station, one group lived in an area with a base station placed on top of their children’s institution (school, etc.) but without any measurement of radiation, and one group represented families with children visiting a school with a base station on the roof and with intense discussions and measurement of radiation available to the parents. The inclusion criterion for the families was presence of at least one child aged 12-14 years and one child below the age of eight. This criterion assured that the interviews would cover adults (users/non-users), adolescents who are about to get or have recently got a mobile phone, and smaller children, where the main focus in relation to a potential risk would be the base stations. All interviews were tape recorded, transcribed, and analysed according to theories from anthropology.

Conclusions
1. Mobile phones have grown into an integrated platform for communication within families, and removal of this communication form is not in question for the families. The importance of dynamics, flexibility, and mobility are symbolised in the mobile phone.
2. The families do not ignore the risk from radiation, but they feel in control because they are able to decide how to use the mobile phone. The advantages outweigh the disadvantages.
3. Health risks associated with the use of mobile phones or an adjacent base station is not an important issue for these families. They are more worried about risks to their children related to unhealthy food, traffic and child molesters.
4. Perceived disadvantages related to mobile phones are primarily related to cost and the nuisance from people talking in public places and at meetings.
5. Credible and unambiguous data on health risks may, however, reduce the use or increase the use of head sets.
6. The families make judgements about the trustworthiness of experts, and they have confidence only in information about risk assessment from impartial organizations or information given from The National Board of Health (Sundhedsstyrelsen).
7. Several parents express their unhappiness with the placement of base stations on top of schools and kindergartens. They state that they feel left out of the decisions to put up the masts. The families seem, however, to accept the presence of the masts after a limited time period, mainly because they do not know what to do about it, and because the only way to cope with a risk you cannot get away from is to accept it or believe in experts who claim that the base stations do not pose any risk to people living in their proximity.
8.

Project team:
Heidi B. Frederiksen, Beth Elverdam, Lina K.Hoel Felde, Jesper B. Nielsen, Ivar S. Kristiansen, University of Southern Denmark