Christensen et al attempt to determine whether cellular telephone use increases the incidence
of brain tumors. [1]
The authors recruited Danish patients with known gliomas and
meningiomas. They also recruited matched control patients, and compared
the incidence, intensity and duration of cell phone use between the two
groups. When no significant difference was demonstrated, the authors
concluded that cellular telephones do not increase the risk of developing
these brain tumors.
The construction of this study does not support this conclusion.
This study was not designed to provide data which could determine if cell
phone users have a higher risk of malignancy than people who do not use
cell phones. Rather, the study provides data which indicate whether
patients with gliomas and meningiomas have a higher risk of using
cellular telephones. Since most brain tumors are not caused by cell phone
use, the answer does little to tell us about whether cell phone use
increased the risk of cancer.
Perhaps a more useful research design would have included a control
group of persons who do not use cell phones (or who use them relatively
infrequently) and an experimental group of frequent cell phone users.
This might have provided a more valid context for testing for any
difference in the incidence of gliomas and meningiomas between the two
groups. It may be that this analysis could be performed using a subset of
Dr. Christensen's existing data.
The authors of this Correspondence report no conflicts of interest.
References
1. Christensen HC,Schüz J, Kosteljanetz M, et al.
Cellular telephones and risk for brain tumors: A population-based, incident case-control study. Neurology,
2005; 64:1189-1195.
The authors of the article had the opportunity to respond to this Correspondence but declined.