A retrospective cohort study was conducted in the Netherlands to test possible changes in prevalence and number of non-specific symptoms in relation to exposure to mobile phone base stations before and after increase of installed antennas at mobile phone base stations.
Data for the baseline period (January - December 2004) were collected retrospectively for the study population of the cross-sectional study by Baliatsas et al. (2015). Inclusion criteria were availability of complete electronic health record data, comparability of symptom data in terms of registration methodology and living in the same house in 2004 and 2011.
Categorization into sensitivity to mobile phone base stations was based on the reports of the participants in 2011.
Overall 55 participants reported to be electrosensitive to mobile phone base stations in 2011.
There was an increase in the total number of antennas at mobile phone base stations of 30% in the period 2004-2011. Mean total calculated electric field strength was 0.10 (±0.15) V/m in 2004 and 0.104 (±0.15) in 2011 for the electrosensitive group; for the rest of the sample mean exposure levels were 0.11 (±0.23) V/m and 0.12 (±0.23) V/m respectively.
A higher prevalence for most non-specific symptoms was observed in the electrosensitive group in 2011 compared to baseline. Exposure estimates were not associated with general practitioner registered non-specific symptoms in the total sample. However, some significant interactions were observed between electrosensitivity and exposure estimates on risk of symptoms.
The authors concluded that by using clinically defined outcomes and a time difference of 6 years it was demonstrated that radiofrequency electromagnetic field exposure to mobile phone base stations was not associated with the development of non-specific symptoms. Nonetheless, there was some indication for a higher risk of non-specific symptoms for the electrosensitive group, mainly in relation to exposure to UMTS, but this should be interpreted with caution.