People with mild haemophilia, a condition that reduces blood clotting, seem to have a slightly longer life expectancy than those without it. This may be because they are less likely to have strokes and heart attacks, which can be caused by blood clots.
The finding comes from the latest figures on outcomes for people with haemophilia in the UK, which suggest that those with milder forms have an average life expectancy of 84 years.
This is 1.7 years more than for UK men as a whole, according to the Office for National Statistics. men.
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Haemophilia is heritable, caused by mutations in a gene that encodes one of the proteins involved in making blood clot after an injury. The most common form involves mutations in the gene that encodes a protein called factor VIII.
Depending on the mutation, people can have varying levels of factor VIII in their blood. If their levels are less than 5 per cent, this is classed as moderate or severe haemophilia and they need regular injections of this protein to avoid internal bleeding, for instance.
But if people have 5 to 40 per cent of the typical factor VIII level, this is classed as mild haemophilia and they don鈥檛 usually bleed spontaneously. Such people may only need factor VIII injections if they are injured or before surgery.
People with any form of haemophilia used to have a much lower life expectancy than average. This has gradually risen over the past few decades, according to a (UKHCDO) released in November.
This is due to a combination of factors, including health systems getting better at identifying people with haemophilia and giving them the right treatments, says at the University of Sheffield in the UK.
Another reason is that in the 1970s and 1980s, many people with haemophilia received products that were contaminated with HIV or the hepatitis C virus. Most of the affected people who are still living are now getting treatments that keep HIV under control or eradicate the hepatitis C virus.
So, for mild haemophilia in the UK, the above-average life expectancy we are now seeing may be a sign of the possible advantages of having blood that is slightly less likely to form potentially dangerous clots, says Makris.
Supporting this idea, in 2022 Makris and his colleagues showed that people with haemophilia are about a third . 鈥淚f you have reduced factor VIII, you鈥檙e less likely to have [these events],鈥� he says.
, who heads the Co-Morbidities Working Party of the UKHCDO, says Makris鈥檚 idea is interesting, but the difference in life expectancy could be a statistical fluke, rather than reflecting a real trend. 鈥淚鈥檇 be cautious about the strength of the conclusion about greater life expectancy because the number of older people with mild haemophilia is small,鈥� she says.
If the finding is borne out by larger studies, however, it could shed light on new ways to prevent heart disease in people without haemophilia, says Shapiro. 鈥淭here may be lessons we can learn from this to apply to the general population.鈥�
