Exposure to radiofrequency fields is increasingly common, but the potential influence on health has not been thoroughly investigated, especially in children. Between 2003 and 2008, there were more than 900 million new cell phone subscribers worldwide, with a total of more than two billion subscribers. The World Health Organization has emphasized the need for research into the possible effects of radiofrequency fields in children. We examined the association between prenatal and postnatal exposure to cell phones and behavioral problems in young children.
This study was based on the Danish National Birth Cohort, which recruited women during pregnancy from March 1996 through November 2002. A total of 101,032 pregnancies were enrolled in the cohort. Mothers and live-born children constitute two fixed cohorts that are to be followed for decades in a life-course perspective. Detailed information on life-style factors, dietary habits and environmental exposures were collected in a series of four telephone interviews from pregnancy to when the newborn reached 18 months. In 2005 and 2006, when the children of those pregnancies had reached 7 years of age, mothers were asked to complete a new questionnaire regarding the current health and behavioral status of children, as well as their cell phone during pregnancy and child's current cell phone use. Mothers evaluated the child's behavior problems using the Strength and Difficulties Questionnaire, which consisted of 25 questions with scaled responses regarding their child's behavior. Based on the specific numerical score, children were classified as abnormal, borderline, or normal for overall behavioral problems as well as for the specific outcomes such as emotional, conduct, hyperactivity, or peer problems.
In the analysis, comparisons were made between baseline characteristics and prenatal and postnatal cell phone exposure. An ordinal logistic regression model was used to estimate the odds of the outcomes of behavioral problems in children according to combined prenatal and postnatal exposure to cell phones, prenatal exposure only, and postnatal exposure only. To evaluate possible dose-response patterns, proxies of prenatal exposure intensity were considered.
Mothers of 13,159 children completed the follow-up questionnaire. Thirty percent of children were using a cell phone at 7 years of age, and about 11 percent of children were exposed to cell phones both prenatally and postnatally. Greater odds ratios for behavioral problems were observed for children who had possible prenatal or postnatal exposure to cell phone use. After adjustment for potential confounders, the odds ratio for a higher overall behavioral problems score was 1.80 (95% confidence intervals = 1.45–2.23) in children with both prenatal and postnatal exposure to cell phones.
Exposure to cell phones prenatally–and, to a lesser degree, postnatally–was associated with behavioral difficulties such as emotional and hyperactivity problems around the age of school entry. These associations may be noncausal and may be due to unmeasured confounding. If real, they would be of public health concern given the widespread use of this technology.