LONDON (Reuters) - Health experts warned yesterday of a stroke crisis in Europe which is already costing the region's economy an estimated €38 billion ($56 billion) a year, with numbers expected to rise as populations age.

In a report for the European Parliament, medical experts working with the campaign group Action for Stroke Prevention, said atrial fibrillation (AF), the most common form of abnormal heart rhythm, affects more than six million people in Europe and increases the risk of stroke by five times.

The economic and health impact of stroke is predicted to grow as the number of people with AF is expected to rise two and a half times by 2050 due to ageing populations, the report said.

It said the economic burden created by patients suffering strokes accounts for two to three percent of total healthcare spending in the European Union and AF is responsible for 15 to 20 percent of all strokes caused by blood clots.

"This burden will increase in years to come, due to both the improved survival of patients with conditions such as heart attacks and Europe's ageing population," the report said.

Gregory Lip, professor of cardiovascular medicine at the University of Birmingham, said the majority of such strokes were preventable, but under-diagnosis and poor care of AF patients, as well as under-use of medicines and the side-effects of drugs means stroke creates "an unnecessary and heavy burden" on patients, carers and health systems.

AF causes the two upper chambers of the heart to quiver instead of beating properly, resulting in blood pooling and potentially forming clots that can cause stroke. Patients can be given anticoagulants, or blood thinners, to help prevent clots.

Stroke is the most common cardiovascular problem after heart disease and kills an estimated 5.7 million people worldwide each year.