5:02 a.m. June 19, 1998 PDT
Mobile phones, an essential accessory for millions of business people and trendy techies, can significantly increase blood pressure, German researchers say.

In a letter to be published in Friday's edition of The Lancet medical journal, Dr. Stephan Braune of the University Neurology Clinic in Freiburg, Germany, said radio-frequency electromagnetic fields (EMF) emitted by the telephones pumped up the blood pressure of 10 young volunteers who took part in a study.

Braune and his team attached the phones to the right side of the volunteers' heads and switched them on by remote control at various intervals.

They measured their heart function and blood pressure while they were standing and lying down. There was no sound so the volunteers did not know when they were exposed to the EMF.

The researchers found that 35 minutes of radio frequency EMF caused "increases in resting [blood pressure] between five and 10 mm."

The finding could have adverse effects on people suffering from high blood pressure or hypertension, an important risk factor for heart disease and stroke which are leading causes of death in most developed countries.

The researchers said the increase in blood pressure probably resulted from constriction of the arteries by the radio-frequency electromagnetic fields.

Cellular telephones have been linked to a variety of health problems ranging from fatigue, headaches, and burning skin to brain tumors, but there is still no proof that the devices pose any serious health risks.

Copyright (c) 2001 Reuters Limited.