A total of 120 frequent users of mobile phones (111 men, 9 women; exposure group) and 102 infrequent users of mobile phones (77 men, 25 women; control group) volunteered for this study. Subjects of the exposure group were employees of an IT company with exposure to mobile base stations and a mobile phone use of more than 5 hours/day. Subjects in the control group had a maximum mobile phone usage of 30 minutes/day.
For parts of the analysis, the exposure group was further divided into subgroups, according to the total number of years of mobile phone usage: 1) mobile phone usage for 1-5 years (n=50), 2) 6-10 years (n=65) and 3) for >10 years (n=5).
In the method section, the authors write: "The make and specific absorption rate of the mobile phones were noted in a questionnaire." However, these data are not presented or mentioned in the further course of the study.
No parameters are specified for this exposure.
The serum levels of C-reactive protein and Hsp70 as well as the gene expression of hsp70 were significantly increased in the exposure group compared to the control group.
The authors conclude that frequent mobile phone use might elevate levels of the stress markers C-reactive protein and Hsp70 in the blood.