Background We previously reported associations between cellphone exposure and emotional and behavioural difficulties in children in the Danish National Birth Cohort using cross-sectional data. To overcome the limitations of cross-sectional analysis, we re-examined these associations with prospectively collected data.
Methods Based on maternal reports, prenatal and postnatal cellphone exposures were assessed at age 7 years, and emotional and behavioural difficulties were assessed at 7 and 11 years with the Strengths and Difficulties Questionnaire. We used multivariable-adjusted logistic regression models to estimate ORs and 95% CIs relating prenatal exposure and age-7 cellphone use to emotional and behavioural difficulties at age 11 years.
Results Children without emotional and behavioural difficulties at age 7 years, but who had cellphone exposures, had increased odds of emotional and behavioural difficulties at age 11 years, with an OR of 1.58 (95% CI 1.34 to 1.86) for children with both prenatal and age-7 cellphone exposures, 1.41 (95% CI 1.20 to 1.66) for prenatal exposure only, and 1.36 (95% CI 1.14 to 1.63) for age-7 use only. These results did not materially change when early adopters were excluded, or when children with emotional and behavioural difficulties at age 7 years were included in the analysis.
Conclusions Our findings are consistent with patterns seen in earlier studies, and suggest that both prenatal and postnatal exposures may be associated with increased risks of emotional and behavioural difficulties in children.
- CHILD HEALTH
- Cohort studies
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Contributors Madhuri Sudan performed the data analyses, drafted and revised the manuscript, and approved the final manuscript as submitted. Leeka Kheifets conceptualised and designed the study, edited the initial manuscript, reviewed and revised the subsequent versions, and approved the final manuscript as submitted. Jorn Olsen conceptualised and designed the study, coordinated and supervised data collection, reviewed and revised the manuscript, and approved the final manuscript as submitted. Onyebuchi A. Arah participated in the analyses, reviewed and revised the manuscript, and approved the final manuscript as submitted. Carsten Obel designed the data collection instruments, critically reviewed the manuscript, and approved the final manuscript as submitted. All authors approved the final manuscript as submitted, and agree to be accountable for all aspects of the work.
Funding This work was supported by funding from the European Community's Seventh Framework Programme FP7/2007-2013 (603794: the GERONIMO project).
Competing interests None declared.
Ethics approval The Danish Data Protection Agency; regional science ethics committees in Denmark; and the Office for the Protection of Research Subjects at UCLA.
Provenance and peer review Not commissioned; externally peer reviewed.