A device worn like a MP3 player could help correct balance problems by signalling when the wearer starts to veer off course.

Balance problems are common in the elderly and can also be caused by certain diseases and medications that weaken the sensory signals we use to stay upright.

The new device uses different sounds that the wearer quickly learns to associate with different positions.

These sounds tell the subject which way they are leaning, so that they can immediately correct the problem before they fall.

"We expect the device to be active by the end of this year," said Marco Dozza, a researcher at the Oregon Health and Science University's neurological sciences institute where the device is being developed.

"And we are discussing the possibility of commercialisation with several companies and expect that the device will be available to buy in the next two years," he said.

To the right, to the left

The device acts like a carpenter's level, which is hooked to the wearer's belt and connected to earphones. When activated, the subjects hear different tones and intensities when they lean out of a central safe zone.

For example, when subjects lean forward they hear a high-pitched tone that gets louder the further forward they tip. If they lean backward, they hear a low-pitched tone.

A tone in the left ear will let the patient know they are leaning left and a tone in the right ear tells them they are leaning too far right.

In a study of 49 patients, including nine with bilateral vestibular loss caused by ototoxic medications, those who used the device tended to sway less. And some subjects unable to stand on a soft cushion with their eyes closed without swaying were able to do so when wearing the device.

Vestibular loss refers to damage to the portions of the inner ear that help us to maintain balance.

"The sound cue is really intuitive," explained Dozza, "and subjects learned to understand them very quickly, usually within about two minutes."

'Teaching' aid

Dozza says that eventually wearers will not have to wear the device all the time, rather they can use it for daily training sessions.

"We believe that this system will facilitate the integration and calibration of other sensory information," he says. In other words, patients will relearn how to use the sensory information they still have, such as vision, to prevent themselves from falling."

Sophie Davison, of Help the Aged in the UK, commented: "Falling remains one of the major causes of injury and death among older people.

"It is vital that more work is done to help prevent falls from happening in the first place and helping those who have already fallen to regain their mobility," she said.

One person dies every five hours in the UK as a result of a fall at home.

Dozza says the device may also be used for rehabilitation and training for sports that require excellent balance, like surfing.