When the children reached seven years of age, mothers were invited to complete a questionnaire that focused on the child's exposures (e.g., maternal mobile phone use during pregnancy, child's mobile phone use at the age of 7 years), lifestyle, and health problems (e.g., migraine or 'often complaints of headaches, stomach aches or sickness').
|Reference group 1||no exposure|
|Group 2||prenatal exposure|
|Group 3||postnatal exposure|
|Group 4||prenatal and postnatal exposure|
|Participation rate||66 %|
According to mothers' reports, 39% out of 52,680 children were exposed prenatally, and 36% used a mobile phone at age seven years (postnatal exposure), but less than 1% used it more than one hour per week. Twenty percent of children were exposed only prenatally, 16% only postnatally, 19% both prenatally and postnatally, and 40% had no reported mobile phone exposure.
Children with mobile phone exposure had an increased risk of migraines and headache-related symptoms than children with no exposure (OR for migraine 1.30 (CI 1.01-1.68); OR for headache-related symptoms 1.32 (CI 1.23-1.40) for children with both prenatal and postnatal exposure).
The authors concluded that in this study mobile phone exposure was associated with headaches in children, but the association may not be causal given the potential for uncontrolled confounding and misclassification in observational studies such as the present study.
The results should be interpreted with caution due to limitations in exposure and outcome assessment. Additional possible confounders such as watching television, playing video games, and use of computers were not covered by the questionnaire.