The research group measured the changes in the amount of blood flow in 10 people, five of whom have symptoms of hypersensitivity to electromagnetic waves. They found that the brain's blood flow in those with the hypersensitivity fluctuated with exposure to the waves.

The findings are expected to contribute to understanding the symptoms, such as headaches and fatigue, for which the causal relationship with electromagnetic waves remains unknown.

The researchers believe the symptoms were caused either because the electromagnetic waves disrupted the nerve system and thus caused changes in the blood flow, or that the ability to maintain the brain's blood flow at a certain level was reduced.

The research involved Ko Sakabe of the Kitasato Institute Hospital and the nongovernmental environment organization Japan Offspring Fund.

Many people with irritations linked to electromagnetic waves also have problems moving their eyeballs and abnormality in their pupils' reaction to light.

"We want to conduct further research with more cases and higher precision," Sakabe said.

There has so far been no method to test for hypersensitivity to electromagnetic waves. One indicator is that symptoms disappear or improve as patients distance themselves from the environment affected by the waves.

In some cases, factors other than electromagnetic waves were said to be the cause of the illnesses.