To the Editor:
We read with interest the paper by Lönn and colleagues1 that examines the association between mobile phone use and acoustic neuroma. It is a well set out paper, and the best study of its kind to date, because, unlike other studies, it has not been limited by a small number of cases and a lack of long-term mobile phone users. We recognize some of the difficulties involved in doing such a study—finding an adequate number of cases could be difficult, and deciding on cutoff points for subjects’ exposure requires careful consideration.
We do, however, question whether the study has been subjected to selective bias with regard to which side of the head the mobile phone was used, ie, a case may be more likely to report using the phone on the same side of the head as the acoustic neuroma has arisen. The article mentions potential confounders, including ionizing radiation and female hormones; without adjusting for such factors, it is difficult to draw strong conclusions on an association between mobile phone use and acoustic neuroma. It would also be interesting to perform a sensitivity analysis on the various exposure categories to identify the relative strength of each category as a potential causative factor.
The findings of this article are suggestive of an increased risk of acoustic neuroma with long-term mobile phone use, and further work is needed to strengthen this association. We question how such research would be achieved because with current use of mobile phones, it would be almost impossible to find subjects with no exposure for a case–control or cohort study.
Bethan N. Thomas
Iain J. Robbé
Welsh College of Medicine, Heath, Cardiff, United Kingdom, Thomas, BN@Cardiff.ac.uk
1. Lönn S, Ahlbom A, Hall P, et al. Mobile phone use and the risk of acoustic neuroma. Epidemiology