Unfair and unreasonable bosses can drive their employees' blood pressure up to an unhealthy level, a new study suggests.

Nadia Wager, a senior lecturer in psychology at Buckinghamshire Chilterns University College in London, and her colleagues recruited 28 female nursing assistants. The women wore monitors that recorded their blood pressure every 30 minutes for three days.

• INDEPTH: The Way We Work

The study was designed to see how blood pressure levels changed in the presence of a supervisor. Thirteen of the nursing assistants alternated between a boss they said they liked and one they didn't.

British nursing assistants change sheets and bedpans

A control group of 15 had one supervisor or two, both of whom were liked or disliked.

On average, the researchers found a 15mm Hg difference in systolic blood pressure and a seven mm Hg difference in diastolic pressure when the subjects worked with a supervisor they considered overbearing.

When they worked under someone they considered fair, their blood pressure decreased slightly. The comparison group showed a three mm Hg rise in systolic pressure and no difference in diastolic while working under the two supervisors.

Over time, high blood pressure can increase the risk of heart disease. A "fair" boss was someone who:

• listened to problems and responded with suggestions
• praised a job well done
• showed trust and respect
• was consistent and impartial

The women said the "unfair" boss did not take input before making decisions or did not treat them fairly.

In Britain, nursing assistants change sheets and clean bedpans under the supervision of nurses. It is considered a poorly paid job with low social status and "high levels of reported work stress and poor health," the researchers said.

• FROM OCT. 17, 2002: Job stress compounds risks for heart disease

Last fall, a larger Finnish study concluded people who had high job strain or felt little reward from their hard work were twice as likely to die of a heart attack or stroke compared to colleagues who were rewarded regularly and treated reasonably.

Wager said she hopes the findings encourage supervisors to reflect on their role and "people management" skills.

For those working under a difficult supervisor, Wager suggests talking to the boss about the problem, if possible. If not, she recommended assertiveness training and focusing on relaxing outside the workplace, such as through exercise.

• FROM MAY 21, 2003: Stress on the job under microscope (CBC Ottawa)

Not all blood pressure problems can be blamed on unfair bosses. Smoking, excessive weight and lack of exercise are regarded as risk factors. Cardiologists say how we deal with the stress is also important.

The study appears in the July 2003 issue of the journal Occupational and Environmental Medicine.