Autores

Abramson MJ, Benke GP, Dimitriadis C, Inyang IO, Sim MR, Wolfe RS, Croft RJ. Mobile telephone use is associated with changes in cognitive function in young adolescents. Bioelectromagnetics. Jul 30, 2009 Ahead of print.

Background
In Australia, mobile phones are owned by 23% of children between the ages of 6 and 13 years.   Health concerns related to radiofrequency (RF) exposure from mobile phones initially focused on tumours; however, there is increasing concern about other effects on the brain, particularly in children whose brain is still developing. There is evidence that mobile phone exposure alters brain activity in young adults.  Previous studies have found that RF exposure was associated with slightly shorter reaction times in children, but these results have not been consistent.

Objective
To address the lack of evidence regarding cognitive biological effects among children, the Mobile Radiofrequency Phone Exposed Users’ Study (MoRPhEUS) was established. The aims were to assess exposure to mobile phones in secondary school students, and to determine whether there were any associations between this exposure and cognitive function.

Methods
During 2005-2006, 13 secondary schools from around Melbourne, Australia were recruited to participate. At each school, one 7th grade class (typical age, 12-13 years) was randomly selected to participate. Of the 479 students who were eligible and who were invited to participate, 317 (66%) consented. Exposure to mobile phones was assessed by questionnaire completed by participating children and their parents. Cognitive function was assessed with a computerised test battery and by the Stroop colour-word test. The battery tested the following cognitive function domains: signal detection, working memory, simple learning, associative learning, and movement monitoring/estimation.

Results
The median age of participants was 13, 54% were girls, and 84% were born in Australia.  Most (94%) had used a mobile phone and 77% had their own phones.  The median total number of reported voice calls per week was 8, as was the median number of reported SMS messages per week. The median reported duration of mobile phone use was 1.74 years.  Students who reported more voice calls per week demonstrated shorter response times for the simple and associative learning tasks.  They also performed less accurately on working memory tests and the associative learning task.  Signal detection and movement monitoring/estimation were not related to the total number of voice calls per week. Students who reported making and receiving more SMS messages demonstrated shorter response times to the simple learning task, but less accurate responses to the working memory and associative learning tasks. Signal detection and movement monitoring/estimation were not related to total SMS messages. There were no significant relationships between duration of mobile phone use and any of the cognitive outcomes.

Interpretation and Limitations
Greater mobile phone use was related to poorer accuracy on working memory and associative learning tasks, and faster reaction times on the simple and associative learning tasks.  In other words, children who used mobile phones were faster but less accurate on a number of tasks, suggesting that they may be more impulsive than other children, favouring a quick, and not accurate solution. Because mobile phone use was assessed at the same time as cognitive function, it was not possible to determine whether RF exposure had affective cognitive function, or if the findings represent pre-existing impulsive behaviours and/or learned behaviours from more frequent use of mobile phones.  For example, texting (SMS) trains users to favour speed over accuracy. Another explanation for these results is that cognitive function drives mobile phone use.

Conclusions
Future epidemiological research should follow participants over time to determine the correct temporal sequence of mobile phone use and cognitive effects. Although the results from this study suggest that cognitive effects associated with mobile phones are subtle, the widespread use of mobile phones means that the association could have considerable public health significance.



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