LONDON: The sight of a doctor’s white coat drives up the blood pressure and the effect is far from negligible, according to a study published in the British Medical Journal on Friday.

The effect means readings taken by doctors are often higher than those taken by nurses or other less intimidating assistants, and effectively that untold numbers of patients may have been prescribed medication without good cause.

A Southampton University team found that blood pressure measured by doctors was typically 19mm higher than ambulatory measurements — automatic measuring devices taking a continuous recording over the day — for systolic pressure and 11mm higher for diastolic pressure.

This would be sufficient to recategorize a healthy person as an at-risk patient.

“It is time to stop using high blood pressure readings documented by general practitioners to make treatment decisions,” the team, led by Paul Little of the Clinical Sciences Division at Southampton University, said.

Blood pressure measurements include two values: the systolic pressure when the heart contracts, and the diastolic pressure when it is relaxing between beats.—dpa