Radiation from mobile phone use may affect the brains of teenagers and harm their memory performance, according to the results of a prospective cohort study of nearly 700 Swiss teenagers. These results confirm those of a previous study the researchers performed in 2015; however, they cautioned that their recent findings, published in Environmental Health Perspectives, need to be duplicated in other populations.
“We found preliminary evidence suggesting that RF-EMF [radiofrequency electromagnetic fields] may affect brain functions such as figural memory in regions that are most exposed during mobile phone use,” wrote researchers led by Martin Röösli, PhD, head of the Environmental Exposures and Health Unit, Swiss Tropical and Public Health Institute, Basel, Switzerland.
Figural memory describes the memory of images, as opposed to verbal memory—the memory of words.
The health effects of RF-EMFs are still unknown, Dr. Röösli and fellow researchers noted. “Neurological functions are of special concern given that the brain is heavily exposed while calling with a mobile or cordless phone. Present-day adolescents will likely have higher cumulative lifetime exposure to RF-EMF, and the developing brain might be particularly susceptible to RF-EMF-induced alterations up to 15 years of age,” they wrote. “In this age group, memory functions are particularly important because proper encoding, processing, and retrieval of information are required for learning.” But studies investigating this topic haven’t yielded consistent results.
For this study—the Health Effects Related to Mobile phone usE in adolescentS (HERMES)—Dr. Röösli and colleagues investigated the relationship between brain exposure to RF-EMF and the development of memory performance in almost 700 adolescents (aged 12 to 17 years) for 1 year. Participants filled out paper questionnaires that assessed their daily mobile phone and media usage, socioeconomic factors, and psychological and somatic health. They performed computerized cognitive testing immediately afterward.
A subgroup of 148 teens, intentionally chosen as representative of the entire study population, were also given portable RF-EMF measurement devices linked to a time-activity app on their smartphones.
When the researchers looked at the objectively reported data from the measurement devices, they found that teens greatly overestimated their self-reported phone use. To correct for this bias, the researchers calibrated self-reported mobile phone use with the objective data. After making this adjustment, the authors determined that the estimated average phone call time for all teens was 10.6 (±13.7) minutes per day, and the estimated average cumulative RF-EMF brain dose was 858 (±1,027) mJ/kg per day.
The researchers found a nonsignificant decrease of 0.22 in figural memory score associated with cumulative RF-EMF brain dose in all participants. The subgroup of teens given the portable RF-EMF measurement device showed a significant 0.26 decrease in figural memory score associated with cumulative RF-EMF brain dose.
Figural memory is mainly located in the right brain hemisphere. The association with figural memory and RF-EMF exposure was more pronounced (a 0.39 decrease) in adolescents using their phones on the right side of the head. “This may suggest that indeed RF-EMF absorbed by the brain is responsible for the observed associations,” Dr. Röösli said.
The researchers found no association with activities—such as texting, gaming, and data usage—that are only marginally related to RF-EMF exposure. They acknowledged that their findings don’t provide conclusive evidence of causal effects and should be interpreted with caution until confirmed in other populations.
“It is not yet clear how RF-EMF could potentially affect brain processes or how relevant our findings are in the long-term,” Dr. Röösli said. But for now, he added, teens should take extra precautions: “Potential risks to the brain can be minimized by using headphones or the loudspeaker while calling, in particular when network quality is low, and the mobile phone is functioning at maximum power.”
This study was funded by the European Community’s Seventh Framework Programme and the Swiss National Science Foundation.