Author's reply to: Occupational and residential exposure to electromagnetic fields and risk of brain tumours in adults: A case-control study in Gironde, France


Dear Sir,

We thank Sir Lloyd Morgan for his careful reading and his interesting comments on our article. We agree that the ratio women to men appears higher in our study than in worldwide registries. The ratio is 3.2 in the French Brain Tumor Registry on the 2000–2007 period, (Baldi et al., submitted) higher than in the United States (2.2),1 but lower than in this study (8.6).

First, we want to point out that this ratio is calculated on a quite small sample: only 67 meningiomas. Then, the 95% confidence interval around the 10.4 % proportion of men observed in this study is [3.1–17.8%], corresponding to a theoretical number of cases in men ranging from 2 to 12 and a theoretical ratio women to men ranging from 4.6 to 32.5.

Second, we want to mention that the 8.6 ratio is calculated on participants only. But 10 women and 9 men with meningiomas did not participate to the study. When calculated on all eligible subjects, the ratio is 4.4 (70/16), ranging from 2.7 to 8.6, a value close to those observed in registries.

Then, in our opinion, the high proportion of men in meningiomas observed in this study is partly due to the small size of the sample, and partly explained by a lower participation of men with meningiomas. This last observation could be due to a poorer prognosis of meningiomas in men in our study (in nonparticipants, three were deceased vs. no women deceased), an hypothesis which deserves further investigation, but which appears consistent with the observation of a male predominance in atypical and malignant meningiomas.2 We do not think it is possible on these sole data to conclude that any risk factor (CEM or others) are responsible for the observation on sex ratio.

Your's sincerely

Isabelle BALDI, Gaëlle COUREAU, Anne GRUBER, Virginie RONDEAU, and Hugues LOISEAU

Isabelle Baldi*, Gaëlle Coureau*, Anne Gruber*, Virginie Rondeau†, Hugues Loiseau‡, * Laboratoire Santé Travail Environnement, Centre INSERM U 893, Université Victor Segalen Bordeaux 2, BORDEAUX, France, † Equipe de Biostatistiques, Centre INSERM U 893, Université Victor Segalen Bordeaux 2, BORDEAUX, France, ‡ Service de Neurochirurgie, CHU Bordeaux, Place Amélie Raba-Léon, BORDEAUX, France.