Trends in cell phone use among children in the Danish national birth cohort at ages 7 and 11 years
Sudan M, Olsen J, Sigsgaard T, Kheifets L. Trends in cell phone use among children in the Danish national birth cohort at ages 7 and 11 years. J Expo Sci Environ Epidemiol. 2016 Mar 23. doi: 10.1038/jes.2016.17. [Epub ahead of print]
We prospectively examined trends in cell phone use among children in the Danish National Birth Cohort.
Cell phone use was assessed at ages 7 and 11 years, and we examined use patterns by age, by year of birth, and in relation to specific individual characteristics.
There was an increase in cell phone use from age 7 (37%) to 11 years (94%). There was a clear pattern of greater reported cell phone use among children at age 7 years with later birth year, but this trend disappeared at age 11. Girls and those who used phones at age 7 talked more often and for longer durations at age 11 years. Low socio-economic status and later year of birth were associated with voice calls at age 7 but not at age 11 years. At age 11 most used cell phones for texting and gaming more than for voice calls. Further, children who started using cell phones at age 7 years were more likely to be heavy cell phone voice users at age 11 years, making early use a marker for higher cumulative exposure regardless of year of birth.
As cell phone technology continues to advance, new use patterns will continue to emerge, and exposure assessment research among children must reflect these trends.
... between 2000 and 2014, the number of active cell phone subscriptions increased from 700 million to nearly 7 billion, among a global population of 7.2 billion people.
Despite the many benefits of this technology, there remain questions about its safety. There is public concern about harmful effects of cell phone use, especially forpotentially vulnerable populations such as children ... Some research also suggests that cell phone use could lead to changes in behavior and cognition, with the potential to affect learning and academic performance among children and adolescents.
In general, the research suggests that cell phone use among children and teenagers is quite common and that they are engaging in a variety of activities on cell phones besides voice calls. However, it is difficult to assess trends in cell phone use over time among these younger users with the existing cross-sectional data because the studies were carried out in different populations and cannot be compared directly.
Cell phone use in the DNBC has so far been assessed at two time points, when the child was 7 years old and again when the child was 11 years old. The age-7 wave of data collection began in April of 2005 and was completed in February of 2011.
When the children reached 11 years of age, a new wave of data collection began in July of 2010 and completed in August of 2014. All mothers and children who were still enrolled in the DNBC were invited to complete the age-11 questionnaires, regardless of their participation in the age-7 wave of data collection.
There were differences in cell phone use between boys and girls, with boys being less likely to use cell phones for communication than girls. Boys were not only less likely to use a cell phone according to mothers’ reports, but at age 11 years, they also self-reported lighter cell phone voice call usage than girls, both in terms of frequency and duration of calls. Although only a small percentage (5%) of children reported keeping their phone in bed with them at night, girls represented the majority of these children. Although only a small percentage of children (<3 activity="" also="" as="" be="" bluetooth="" boys.="" boys="" br="" but="" by="" children="" dominated="" first="" games="" girls.="" girls="" hands-free="" headphones="" kind="" likely="" messaging="" more="" most="" of="" on="" or="" percent="" performed="" phone="" phones="" playing="" ranked="" report="" reported="" second-most="" second="" sixty-eight="" some="" speakerphone="" speaking="" technology="" text="" than="" the="" their="" they="" this="" to="" using="" was="" were="" when="" while="">
With the rapid growth of cell phone use and its increasing popularity among children, our results are in line with societal trends. Our prospective evaluation of cell phone use over time provides information to guide exposure assessment methods and analyses in future epidemiologic studies of cell phone use among children. In particular, our findings suggest that studies among children should consider cell phone use both prior to and during adolescence and include assessments of various cell phone activities besides voice calls, including text messaging and gaming. Although our study did not directly assess additional cell phone activities such as social media and internet usage, we also expect these activities to be popular among older children and adolescents. As cell phone technology continues to advance, new use patterns will continue to emerge.
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
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