Paris - Bosses who are disliked for being unfair or unreasonable can stoke a massive rise in workers' blood pressure, a phenomenon that fuels the risk of a heart attack or stroke, a study revealed on Monday.
Scientists recruited 28 female nursing assistants in British hospitals and monitored their blood pressure every 30 minutes to see how it changed in the presence of their supervisor.
Thirteen of the 28 had two supervisors, who alternated during their working week - one workers liked, and the other they disliked.
The 15 others were a comparison group: they either had just one supervisor or two, both of whom were liked or disliked.
Those who had to alternate with Ms Nice and Ms Nasty had an astonishing difference in blood pressure, the researchers found.
They registered a 15mm Hg difference in their systolic blood pressure, and a 7mm Hg difference in diastolic pressure, when they had to work with a supervisor they considered overbearing.
But when they worked under someone they considered fair, they were more relaxed - their blood pressure went down.
Previous studies have found that increase of 10mm Hg in systolic and 5mm Hg in diastolic blood pressure can lead to a 16 percent increased risk of coronary heart disease and a 38 percent increased risk of stroke.
A "fair" boss was considered someone who listened to problems, responded to suggestions, praised a job well done, showed trust and respect and was consistent and impartial.
Meanwhile, the comparison group registered only a tiny difference of 3mm of mercury (Hg) in their systolic pressure, and no difference in diastolic, when working with their two different supervisors.
The study, conducted by doctors at Buckinghamshire Chilterns University College in southern England, is printed in Occupational And Environmental Medicine, a publication of the British Medical Association.
Nursing assistants carry out many of the menial jobs in hospitals, such as changing sheets and cleaning bedpans, and are under the supervision of nurses.
They are poorly paid, have low social status, "high levels of reported work stress and poor health", the authors say.
A Finnish study published last October found people who suffer from stressful demands at work, poor rewards and scant career opportunities are twice as likely to die from heart disease than colleagues who were treated reasonably and given regular rewards.