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. 2012;7(4):e34453.
doi: 10.1371/journal.pone.0034453. Epub 2012 Apr 30.

Mobile phones and multiple sclerosis--a nationwide cohort study in Denmark

Aslak Harbo Poulsen  1 , Egon Stenager, Christoffer Johansen, Joan Bentzen, Søren Friis, Joachim Schüz
Affiliations

Mobile phones and multiple sclerosis--a nationwide cohort study in Denmark

Aslak Harbo Poulsen et al. PLoS One. 2012.

Abstract

We investigated the risk of, prognosis of and symptoms of multiple sclerosis (MS) among all Danish residents who owned a mobile phone subscription before 1996. Using the Danish Multiple Sclerosis Registry and Civil Registration System, study subjects were followed up for MS through 2004. Poisson models were used to calculate incidence rate ratios (IRR, age range: 18-64 years) and mortality rate ratios (MRR, age range: 18+) and to compare presenting symptoms among subscribers and all non-subscribers. A total of 405 971 subscription holders accrued four million years of follow up, with men accounting for 86% of the observation time. Among subscription holding men, the IRR of MS was close to unity, overall as well as 13+ years after first subscription (IRR 1.02, 95% CI: 0.48-2.16). Among women, the IRR was 3.43 (95% CI: 0.86-13.72) 13+ years after first subscription, however, based on only two cases. Presenting symptoms of MS differed between subscribers and non-subscribers (p = 0.03), with slightly increased risk of diplopia in both genders (IRR: 1.38, 95% CI: 1.02-1.86), an increased risk of fatigue among women (IRR: 3.02, 95% CI: 1.45-6.28), and of optic neuritis among men (IRR: 1.38, 95% CI: 1.03-1.86). Overall the MRR was close to one (MRR: 0.91, 95%CI 0.70-1.19) among MS-patients with a subscription and although we observed some increased MRR estimates among women, these were based on small numbers. In conclusion, we found little evidence for a pronounced association between mobile phone use and risk of MS or mortality rate among MS patients. Symptoms of MS differed between subscribers and nonsubscribers for symptoms previously suggested to be associated with mobile phone use. This deserves further attention, as does the increased long-term risk of MS among female subscribers, although small numbers and lack of consistency between genders prevent causal interpretation.

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Conflict of interest statement

Competing Interests: Since 1994, CJ has been a Consultant to the Danish National Board of Health in the area electromagnetic fields and health and received support from Sonofon and TeleDenmark Mobile for the establishment of the nationwide cohort in 1999. ES has received financial support for congress participation from Bayer Schering, Merck Serono, Biogen Idec, Sanofi Aventis and Novartis and unrestricted research grants from Bayer Schering, Merck Serono, and Biogen Idec. There are no patents, products in development or marketed products to declare. This does not alter the authors’ adherence to all the PLoS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Figures

Figure 1
Figure 1
Mobile phone subscription penetration in the Danish population by age in 1990 and 1995.
See this image and copyright information in PMC

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