LONDONIron deficiency may increase stroke risk by making the blood more sticky, according to a new study published in the journal PLOS ONE. The findings could ultimately help with stroke prevention.

Every year, 15 million people worldwide suffer a stroke. Nearly six million die and another five million are left permanently disabled. The most common type, ischaemic stroke, occurs because the blood supply to the brain is interrupted by small clots.

Scientists at Imperial College London studied a group of patients with a rare disease called hereditary haemorrhagic telangiectasia (HHT) that often leads to enlarged blood vessels in the lungs, similar to varicose veins. Normally, the lungs' blood vessels act as a filter to remove small clots before blood goes into arteries. In patients with abnormal lung vessels, blood is able to bypass the filter, so small blood clots can travel to the brain.

Researchers found that iron deficiency increases the stickiness of small blood cells called platelets, which initiate blood clotting when they stick togetherthe patients in the study who were short of iron were more likely to have a stroke. Of the 497 patients, those with even moderately low iron levelsaround 6 micromoles per literapproximately doubled the risk of stroke compared with levels in the middle of the normal range of 7-27 micromoles per liter.

In addition, the researchers looked at platelets in the lab and found that when they treated these with a substance that triggers clotting, platelets from people with low iron levels clumped together more quickly.

"Since platelets in the blood stick together more if you are short of iron, we think this may explain why being short of iron can lead to strokes, though much more research will be needed to prove this link," said Claire Shovlin, Ph.D., from the National Heart and Lung Institute, Imperial College London. "The next step is to test whether we can reduce high-risk patients' chances of having a stroke by treating their iron deficiency. We will be able to look at whether their platelets become less sticky. There are many additional steps from a clot blocking a blood vessel to the final stroke developing, so it is still unclear just how important sticky platelets are to the overall process."

In another recent study, researchers found eating foods that contain vitamin C may reduce the risk of the most common type of hemorrhagic strokeon average, the people who had a stroke had depleted levels of vitamin C, while those who had not had a stroke had normal levels of the vitamin.