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Mobile phone use and acoustic neuroma risk in Japan

Toru Takebayashi 1, Suminori Akiba 2, Yuriko Kikuchi 1, Masao Taki 3, Kanako Wake 4, Soichi Watanabe 4 and

Naohito Yamaguchi 5*

1 Keio University School of Medicine, Japan
2 Kagoshima University Graduate School of Medical and Dental Sciences, Japan
3 Tokyo Metropolitan University, Japan
4 National Institute of Information and Communications Technology, Japan
5 Tokyo Women's Medical University, Japan

Objectives: The rapid increase of mobile phone use has increased public concern about its possible health effects

in Japan, where the mobile phone system is unique in terms of the characteristics of the signal transmission. To examine the relationship between mobile phone use and acoustic neuroma, a case-control study was initiated.

Methods: The study followed the common, core protocol of the international collaborative study, INTERPHONE study. A prospective case recruitment was done in Japan for 2000-2004. One hundred and one acoustic neuroma cases, who were 30-69 years of age and resided in the Tokyo area, and 339 age-, sex-, and residency-matched controls were interviewed using a common computer-assisted personal interview system. Education- and marital status-adjusted odds ratio was calculated with a conditional logistic regression analysis. Results: Fifty-one cases

(52.6%) and 192 controls (58.2%) were regular mobile phone users on the reference date, which was set as 1 year before the diagnosis, and no significant increase of acoustic neuroma risk was observed, with the odds ratio (OR) being 0.73 (95% confidence interval : 0.43-1.23). No exposure-related increase in the risk of acoustic neuroma was observed when the cumulative length of use (<4 years, 4-8 years, >8years) or cumulative call time (<300 h, 300-900 h, >900h) was used as an exposure index. The OR was 1.09 (95%CI:0.58-2.06) when the reference date was set as 5 years before the diagnosis. Further, laterality of mobile phone use was not associated with tumors. Conclusions: These results suggest that there is no significant increase in the risk of acoustic neuroma in association with mobile phone use in Japan.


Today’s publication of a population-based case-control study of acoustic neuromas in the British Journal of Cancer1is the latest in a series of studies published as part of the internationally coordinated INTERPHONE project. This particular study involvesdata from five countries: Denmark, Sweden, Finland, Norway and the United Kingdom.
The data used from Sweden and Denmark has been published separately2. By way of background, acoustic neuroma is a rare, benign and often slow-growing tumor of the nerve that connects the ear to the brain and it may be detected due toeffects on hearing. It has a natural yearly incidence rate of about 1 per 100,000.In the present study, the authors reached the following conclusion:"Thus on balance, the evidence suggests that there is no substantial risk ofacoustic neuroma in the first decade of use, but the possibility of some effectafter longer periods remains open."In the press release accompanying the release of the paper the authors are quotedas saying: “The study found no relation between the risk of acoustic neuroma and the number of years for which mobile phones had been used, the time since firstuse, the total hours of use or the total number of calls, nor were there anyrelations separately for analogue or digital phone use.”We note that this result is consistent with previous studies and the significant bodyof research reporting no health risk from using mobile phones. The authors say
thatthe data was insufficient for a clear interpretation of possible risk after use of aphone for 10 years or longer.As already mentioned, this study is an analysis of some of the national data collectedas part of a 13 country INTERPHONE project coordinated by the InternationalAgency for Research on Cancer (IARC). As these diseases are rare, large numbers ofsubjects are needed for accuracy and IARC will follow with an overall analysisinvolving the combined data from all 13 countries. Therefore, it is necessary to wait for the results of the combined analysis, which is due in mid 2006. The mobile phone industry takes all questions regarding the safety of mobile phonesseriously and we have a strong commitment to supporting ongoing scientific research – such as the INTERPHONE project. This particular project is being fundedby the mobile phone industry jointly with governments and national health agenciesin a way that ensures the complete scientific independence of the work carried out.It as also important to note that all mobile phones sold comply with internationalhealth and safety exposure
guidelines.Mobile phone use and the risk of acoustic neuroma:results of the Interphone case-control study in fiveNorthern European countries. (MJ Schoemaker et al) 30 August 2005

1See Schoemaker et. Al. Mobile phone use and risk of acoustic neuroma: results of the Interphone case-control study in five Northern European countries. BritishJournal of Cancer.
Exposure to loud noise and risk of acoustic neuroma
The incidence of acoustic neuroma has increased over the past 20 years and is currently 1–20 per million population per year in most industrialized countries . This increase in incidence may be due to better diagnostic tools and increased awareness of the disease; however, a number of environmental factors including electromagnetic fields emitted by hand-held cellular telephones have also been implicated . More recently, the role of loud noise exposure in acoustic neuroma aetiology has been evaluated by Edwards et al. . Prior to this, the only
available study examining loud noise exposure and acoustic neuroma risk was in the 1980s and was limited by the small number of cases available for inclusion in the analysis, as well as by the restriction of the study population to men . As a secondary aim of the Swedish portion of the Interphone Study (an international multicentre case–control study of brain tumours, acoustic neuromas and parotid gland tumours in relation to mobile phone use and other
potential risk factors) , Edwards et al. evaluated the role of loud noise exposure as a potential acoustic neuroma

risk factor.
The study was a population-based case–control study that included all individuals aged 20–69 years who resided in three geographic regions covered by the three regional cancer registries in Sweden. Eligible cases were all patients diagnosed with acoustic neuroma (using International Classification of Diseases, Tenth Revision, and International Classification of Diseases for Oncology, Second Edition) over a 3-year period. Controls were randomly
selected from the study base and were frequency matched on age, sex and residential area. A total of 146 cases with acoustic neuroma and 564 controls were included in the study.
Data collection was by means of face-to-face interviews conducted by either a study nurse or the study neuropsychologist, and study participants were specifically asked about occupational and regular non-occupational exposure to loud noise (exposure to loud noise being defined as that exceeding a level of 85 dB).
The total years of loud noise exposure were then categorized into <5, 5–14 and 15 years. Loud noise exposure was also categorized into the following groups:

(i) exposure to machines, power tools and/or construction;

(ii) exposure to motors, including airplanes;

(iii) exposure to loud music, including employment in the music industry;

(iv) exposure to screaming children, sports events and/or restaurants or bars and

(v) other types of loud noise exposure.

Data regarding the use of hearing protection were also collected.
Unconditional logistic regression models adjusted for age, sex and local cancer registry region were used to estimate odds ratios (ORs) and their respective 95% confidence intervals (CIs). In the analysis of loud noise exposure type, adjustments were also made for highest level of education as a proxy for socio-economic status.
Tests for trend were calculated by use of the Cochran–Armitage test for trend.
The results revealed that individuals reporting loud noise exposure from any source were at increased risk for acoustic neuroma (OR = 1.55, 95% CI = 1.04–2.30). Exposure to loud noise from machines, power tools and/or construction increased the risk for acoustic neuroma (OR = 1.79, 95% CI = 1.11–2.89), as did exposure to loud music (OR = 2.25, 95% CI = 1.20–4.23). The OR for a latency period of 13 or more years since the first loud noise exposure from any source was 2.12 (95% CI = 1.40–3.20).
Edwards et al. concluded that the result of the study supports the hypothesis that loud noise exposure is a risk factor for acoustic neuroma; however, further research is needed to validate self-reports of loud noise exposure and to evaluate the effect of potential detection bias