In a review of medical literature, researchers at the University of Exeter found that a difference in the so-called systolic blood pressure between arms can be a useful indicator of the likelihood of heart trouble.

People with high blood pressure -- also called hypertension -- have an increased risk of developing heart disease, stroke, kidney disease and dementia, previous research has shown.

High blood pressure is defined by the World Health Organisation (WHO) as 140 over 90 millimetres of mercury or more. Mercury is used in blood-pressure gauges.

The first number measures maximum heart pressure (systolic), while the second measures pressure when the heart is in a resting phase (diastolic).

Published in the British medical journal The Lancet, the findings suggest that both-arm blood pressure checks should become standard practise, the researchers said.

The probe reviewed 28 studies with data on the difference in systolic blood pressure between arms.

They concluded that a gap of 15mm of mercury or more was linked with an increased risk of the narrowing and hardening of the arteries that supply blood to the legs and feet.

It was also associated with pre-existing cerebrovascular disease, which affects blood supply to the brain and can contribute to dementia.

Above this threshold, death rates due to cardiovascular problems likewise went up.

Most such cases are "clinically silent" and double-arm checks would better identify those at risk, the study said. (AFP)