The risk of having a stroke — particularly the kind that results from a blood clot or other obstacle traveling from the heart — appears to be greater in people who have higher levels of iron, according to recent research.
Scientists from Imperial College London in the United Kingdom examined stroke risk in people for whom they had information on their levels of iron and whether they had genetic differences that altered their iron status.
This yielded evidence suggesting that those with "genetically determined higher" iron levels were at greater risk of having a stroke, they note in a report on the study that now features in the journal Stroke.
In addition, it seems "that this effect is driven by an increased risk of cardioembolic stroke," a type of stroke in which blood in a vessel supplying the brain is blocked due to an obstruction that has traveled from the heart.
The study authors caution, however, that people should not use these findings as a reason to try to alter their iron levels, and they call for further research to confirm their results and also find out why iron may have this effect.
"This is an early-stage finding," notes lead study author Dr. Dipender Gill, from the School of Public Health at Imperial College London, "and we would certainly not recommend that patients at risk of stroke reduce their iron intake, as it has many crucial roles in the body."
Cardioembolic stroke and iron status
According to the World Health Organization (WHO), around 15 million people have a stroke every year. Of these, 5 million die as a result and another 5 million will be disabled for the rest of their lives.
In the United States, more than 795,000 people have a stroke every year and about 140,000 die, accounting for 1 out of 20 deaths.
The majority of strokes are of the ischemic type, which occurs when a blockage in a blood vessel has stopped oxygen- and nutrient-rich blood reaching the affected part of the brain.
Cardioembolic stroke accounts for a notable proportion of ischemic strokes and is often linked to a heart condition called atrial fibrillation, wherein the heart beats irregularly and often faster than normal.
Iron has many uses in the body, the main one being to carry oxygen in red blood cells. The authors explain that studies have examined links between iron levels and stroke risk, but the results have been "conflicting."
Some studies, for example, have tied a raised risk of stroke to low levels of iron, while others have tied it to high levels of iron. In addition, there have also been studies that have found no link at all.
Genetically driven iron status
Dr. Gill explains that they decided to investigate further because there have also been studies that have "suggested that in some cases iron can [actually] trigger blood to form a clot."
The first part of the team's investigation involved identifying genetic differences that influence how much iron people have, which is known as their "iron status."
They searched public data sources that held genetic information on more than 48,000 people.
Using a technique called Mendelian randomization, the scientists identified three "single-letter alterations," or single nucleotide polymorphisms (SNPs), in their DNA that can raise or reduce an individual's iron status.
They then used the three SNPs to screen another genetic dataset covering 60,000 people who had experienced strokes.
They found that people with SNPs that can raise iron status were the ones most likely to have cardioembolic strokes.
'Avenues for further study'
The team has also used Mendelian randomization to explore other factors that may have an impact on stroke risk.
This revealed that people who have more blood platelets, or cells that promote clotting and stop bleeding, could be at higher risk for ischemic stroke.
Another investigation led to the discovery that individuals low in Factor XI, which is a compound that also helps blood clotting, could be at reduced risk of cardioembolic stroke.
"All these findings highlight potential treatments or lifestyle interventions that may help reduce stroke risk, and that they may offer avenues for further study."
Dr. Dipender Gill