Divan HA, Kheifets L, Obel C, Olsen J. Cell phone use and behavioural problems in young children. J Epidemiol Community Health. Dec 7, 2010 Ahead of print.
Cellular communications and other radiofrequency technologies have rapidly increased in the past decade. Of special concern is the use of cell phones by pregnant women and young children. Potential health effects of cell phone use in children have not been adequately studied and have been identified as the highest research priority. Previously, the authors reported that prenatal and postnatal exposure to cell phones was associated with more behavioral problems at age 7 years in ~13,000 children from the Danish National Birth Cohort (DNBC).
The objective was to analyze a larger separate group of mothers and children from the DNBC considering additional confounders and to find out if this analysis would produce similar results.
The new cohort included 28,745 children. Information on lifestyle factors, diet and environmental exposures was collected from mothers by telephone interviews. Two interviews were conducted during pregnancy and two within 18 months postpartum. When the children reached 7 years of age, the mothers were administered a questionnaire containing questions on children’s health, mobile phone use by the mother during pregnancy and by the child, family lifestyle, social conditions, child’s diseases and behavioral problems. Mothers gave scaled responses (very true, partly true or not true) regarding their children’s behaviors. Scores were summed, and children were classified as normal, borderline or abnormal using a priori defined cut-off points. Analyzes were adjusted for covariates from the original analyses and some other potentially important covariates. Results are presented for both the new and the original cohort for comparison.
The proportions of children using a cell phone at age 7 were 30.5% and 35.2% in the original and in the new cohort, respectively. In both datasets, less than 1% of children used a cell phone for more than 1 hour per week. Ten percent of children in the original dataset and 18% in the new dataset were exposed to cell phones both prenatally and postnatally. In both cohorts, ~93% of children were classified as normal, ~3% as borderline and ~3% - as abnormal. In both cohorts, the highest OR for behavioral problems was seen for children who had a joint (prenatal and postnatal) exposure compared with no exposure: OR= 1.9 (95% CI 1.5-2.3) and OR=1.5 (95% CI 1.3-1.7) in the original and in the new cohort, respectively. In the combined dataset (the original plus the new), the OR adjusted for additional covariates was 1.5 (95% CI 1.4-1.7) for prenatal and postnatal exposure, 1.4 (95% CI 1.2-1.5) for prenatal exposure only and 1.2 (95% CI 1.0-1.3) for postnatal exposure.
Interpretation and Conclusion
Using a new group of participants from the same cohort, the authors replicated results of their earlier study. These new results make it unlikely that the previously reported association was a chance finding. The authors note that, although it is premature to interpret the observed association as causal, precautionary measures might be warranted.