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Background Children today are exposed to cell phones early in life, and may be the most vulnerable if exposure is harmful to health. We investigated the association between cell phone use and hearing loss in children. Methods The Danish National Birth Cohort ( DNBC) enrolled pregnant women between 1996 and 2002. Detailed interviews were conducted during gestation, and when the children were 6 months, 18 months and 7 years of age. We used multivariable-adjusted logistic regression, marginal structural models ( MSM) with inverse-probability weighting, and doubly robust estimation ( DRE) to relate hearing loss at age 18 months to cell phone use at age 7 years, and to investigate cell phone use reported at age 7 in relation to hearing loss at age 7. Results Our analyses included data from 52 680 children. We observed weak associations between cell phone use and hearing loss at age 7, with odds ratios and 95% confidence intervals from the traditional logistic regression, MSM and DRE models being 1.21 [95% confidence interval [CI] 0.99, 1.46], 1.23 [95% CI 1.01, 1.49] and 1.22 [95% CI 1.00, 1.49], respectively. Conclusions Our findings could have been affected by various biases and are not sufficient to conclude that cell phone exposures have an effect on hearing. This is the first large-scale epidemiologic study to investigate this potentially important association among children, and replication of these findings is needed. [ABSTRACT FROM AUTHOR]

The article presents the author's response to the comment on their study on the causal inference in perinatal and pediatric epidemiology, published in this issue. They focus on the need for multiple bias modeling. They disagree with the view that bias analysis must be preceded by placement of the unmeasured confounder.

A reply to a letter to the editor in response to an article on perinatal epidemiology that was published in the May 2013 issue of the journal "Paediatric and Perinatal Epidemiology" is presented.