An international study involving the University of Southampton has shown people who undergo a total hip replacement are at a higher risk of a stroke in the first two weeks after surgery.

The cohort study, published in the American Heart Association journal Stroke, assessed about 66,000 people in the Netherlands who had total hip replacements and compared them to people who shared their age and sex, but who did not have the procedure.

Results showed that patients were five times as likely to have an ischaemic stroke within the first two weeks after a total hip replacement and were four times as likely to have a haemorrhagic stroke after the same procedure.

After the first two weeks, the risk dropped steadily but remained elevated during at least the first six weeks for ischaemic stroke and the first 12 weeks for haemorrhagic stroke.

A haemorrhagic stroke is caused by bleeding in the brain and an ischemic stroke is caused by artery blockage.

However another aspect of the study, which was the largest one of its kind, demonstrated that patients who took antiplatelet drugs, such as aspirin, prior to surgery lowered their risk of ischaemic stroke in the first six weeks by 70%. There was no change for haemorrhagic stroke.

Professor Cyrus Cooper Director of the Medical Research Council Lifecourse Epidemiology Unit, University of Southampton, was lead Rheumatologist of the study and co-author of the study's paper.

He comments: "This research has demonstrated that there is a high risk of stroke to patients soon after having a total hip replacement and suggests that the use of soluble aspirin might be beneficial in reducing this risk. Normally we would have reservations about people taking aspirin everyday but our results suggest aspirin is a benefit and worthwhile to give to the patient before the surgery. The data is of huge clinical importance and shows the benefits of large cohort epidemiology studies.

"The number of hip replacement procedures will rise as we live longer: on average, the rate of hip replacement has already increased by over 25% between 2000 and 2009. These results will hopefully help healthcare professionals to provide improved services and help people who have hip replacements manage the risk of stroke after the procedure."

There are a number of factors that contribute to the risk of stroke after surgery: the blood to the brain can be dilated during surgery, blood clots can also form in blood vessels in the brain and there can be disorder to heart rhythms which increases risk of stroke. Additionally the effects of the anaesthetic can contribute to the risk of stroke.

In England and Wales there are approximately 160,000 total hip and knee replacement procedures performed each year.