Early Cell Phone Exposure Again Linked to Behavior Problems in Children

Megan Brooks

December 09, 2010

December 9, 2010 — A new study provides more evidence that exposure to cell phones prenatally and early in life may increase a child's risk of developing behavioral problems.

"Although it is premature to interpret these results as causal, we are concerned that early exposure to cell phones could carry a risk, which, if real, would be a public health concern given the widespread use of this technology," investigators from the University of California, Los Angeles, conclude.

The study was published online December 7 in the Journal of Epidemiology and Community Health.

Led by Leeka Kheifets, PhD, the study examined cell phone use and behavior among 28,745 children and their mothers in the Danish National Birth Cohort Study.

The study enrolled nearly 100,000 pregnant women between 1996 and 2002 with the intention of tracking their children's long-term health. The women provided information on their lifestyle, including cell phone use during and after pregnancy, as well as their child's cell phone habits and behavioral issues when their child turned 7 years old.

Overall, 35.2% of the children were using a cell phone at the age of 7 years, but less than 1% used it for more than 1 hour per week. The vast majority of children (93.0%) had no behavioral issues, 3.3% had borderline behavioral problems, and 3.1% showed signs of behavioral problems, including emotional symptoms, conduct problems, hyperactivity/inattention, and relationship problems.

According to the investigators, 17.9% of children were exposed to cell phones both prenatally and after birth, and these children had the highest adjusted odds ratio (aOR) for behavioral problems (aOR, 1.5; 95% confidence interval [CI], 1.4 – 1.7; compared with children not exposed during either period).

For prenatal or postnatal cell phone exposure, the aORs were 1.4 (95% CI, 1.2 – 1.5) and 1.2 (95% CI, 1.0 – 1.3), respectively.

The researchers adjusted for a variety of potential confounding factors, including sex of the child, mother's age at birth, mother's and father's history of psychiatry, cognitive or behavioral problems as a child, combined socio-occupational status, gestational age, mother's prenatal stress, and child breastfed up to 6 months of age.

Confirmatory Findings

Dr. Kheifets and colleagues say this latest study backs their previous, smaller study of nearly 13,000 children from the same Danish National Birth Cohort Study (Epidemiology. 2008;19:523-529).

"This replication in a larger separate group of children from the same Danish cohort makes it less likely that the findings in the first study were due to chance," Martine Vrijheid, PhD, of the Centre for Research in Environmental Epidemiology, Barcelona, Spain, who was not involved in the study, told Medscape Medical News. "Overall, this seems to be a very thorough study."

Dr. Kheifets noted that questions have been raised about whether their earlier results were limited to "early technology adopters; it does not appear to be so," she said. "Also, we have examined additional factors and found that they are not the reason for observed association. Thus, this [new] work broadly confirms our previous finding, although the association became a bit weaker," with an aOR of 1.5 vs 1.9 in the earlier study.

She added that since 2008, "3 other studies have reported similar results with various outcome instruments and exposure assessment methods and confounding control.

"We do not know of a strong biological mechanism for these effects, especially with regard to the prenatal exposures. Indeed, the exposure of the fetus to phone use of the mother is likely to be very low," said Dr. Vrijheid.

"Also, exposure assessment based on recollection is far from ideal," Dr. Kheifets added.

"Of course, the jury is still out" on this issue, she emphasized. "It is our hope that other scientists will attempt to replicate or refute the findings of our research based upon similar study designs," the investigators write.

The study authors and Dr. Vrijheid have disclosed no relevant financial relationships.

J Epidemiol Community Health. Published online December 7, 2010.

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