Researchers say they have found a connection between mobile phone use and increased brain activity.

American scientists found that 50 minutes of mobile phone use was associated with increased “brain glucose metabolism” – a marker of brain activity – in the region closest to the phone antenna.

However, the health implications of the finding are unknown, they say in last week’s issue of the Journal of the American Medical Association.

The article points out that there have been concerns regarding potential harmful effects of exposure to radiofrequency-modulated electromagnetic fields (RF-EMFs) of mobile phones. But studies of the association between mobile phone use and prevalence of brain tumors have been inconsistent and remain unresolved, they say.

Nora D Volkow, of the National Institutes of Health in Bethesda, Maryland, and colleagues conducted a study involving 47 people.

Mobile phones were placed on the left and right ears and brain imaging was performed to measure brain glucose metabolism twice, once with the right phone activated – but with the sound muted – for 50 minutes and once with both phones deactivated.

The researchers found that whole-brain metabolism did not differ between the on and off conditions – but there were significant “regional” effects.

Metabolism in the brain region closest to the antenna (orbitofrontal cortex and temporal pole) was significantly higher (approximately seven per cent) for “mobile phone on” than “mobile phone off” conditions.

The researchers write: “Results of this study provide evidence that acute cell (mobile) phone exposure affects brain metabolic activity. However, these results provide no information as to their relevance regarding potential carcinogenic effects (or lack of such effects) from chronic cell phone use.

“Further studies are needed to assess if these effects could have potential long-term harmful consequences.”