The study was conducted by researchers at Buckinghamshire Chilterns University College in England.

They found that the blood pressure of healthcare assistants was higher when they were supervised by someone they considered unreasonable.

In a report in the journal of Occupational and Environmental Medicine, Dr. Nadia Wager said, "An unfavourably perceived supervisor is a potent workplace stressor, which might have a clinically significant impact on supervisees' cardiovascular functioning."

Researchers measured the blood pressure of 28 healthcare workers every half hour for 12 hours over three days. They compared the results with their evalutations of nurses who had supervised them.

They noted an increase of 10 millimetres of mercury (mm/hg) in systolic and five mm/hg in diastolic blood pressure when the assistants worked with a supervisor whom they had considered unfair.

But when they were supervised by someone they thought was reasonable and fair, their blood pressure dropped.

Systolic is the pressure of the contracting heart and diastolic is the pressure of the resting heart.

When an individual experiences an increase of 10 mm/hg in systolic and five mm/hg in diastolic blood pressure, the risk of coronary heart disease increases by 16 percent. But the risk of stroke increases by a staggering 38 percent, according to the researchers.

The World Health Organisation says cardiovascular disease kills an estimated 16.6 million people, or one-third of total global deaths, each year. High blood pressure, raised cholesterol levels, lack of exercise, smoking, excessive weight and a poor diet are leading risk factors.