Risk factors

Study supports theory that haemophilia protects against CVD

Researchers have found a lower than predicted incidence of cardiovascular disease (CVD) in patents with haemophilia, which they say supports the theory that the blood disorder protects against the development of CVD.

The prospective, multicentre, observational study, undertaken in the UK and the Netherlands and based on 570 people with haemophilia followed up for five years, also found no statistically significant link between the severity of haemophilia and CVD incidence.

According to the data, published in Blood Advances, the actual number of fatal and nonfatal CVD events in the cohort was lower than that predicted, at 9 vs 24, equating to an absolute risk reduction of 2.4%, seen across all types of haemophilia severities.

A “considerable risk reduction” was also seen in all cardiovascular risk groups, the authors noted, with a relative risk (RR) score of 0.33 for the high-risk group, 0.43 for the intermediate-risk group, and 0.17 for the low-risk group.

The results also showed that for haemophilia patients treated on demand (n=122) no CVD events were observed compared to 5 predicted (RR 0), while for those on prophylactic therapy (n=182), 4 were observed versus 7 predicted (RR, 0.57).

And in a head-to-head comparison for treatment type, the researchers found no significant difference in CVD events between people with haemophilia treated on-demand and on-prophylaxis, nor in QRISK score.

Logistic regression analysis showed a significant correlation between QRISK score and the occurrence of CVD events (odds ratio, 1.118), the researchers said, and also noted that adjustment for factor level did not change this result.

“When severity of haemophilia in relation to CVD occurrence was analysed, we found no differences; particularly, severe haemophilia with on-demand therapy did not differ from mild haemophilia.”

The authors concluded that the findings indicate that the QRISK “overestimates CVD events in patients with haemophilia,” and that “all people with haemophilia might be reclassified to a lower cardiovascular risk group”.

Also, the fact that patients with severe haemophilia treated on demand had the highest risk reduction backs the theory that very low factor VIII or IX activity levels have a protective effect against thrombotic CVD, they said.

They said the mechanism by which haemophilia may protect against CVD was not certain, and it was known that it does not protect against atherosclerosis.

The authors hypothesized that lower clotting factor levels diminish pathologic clot formation at sites of unstable plaques in people with haemophilia.

Supporting this theory is the efficacy of antithrombotic medications, which lower clot formation to reduce CVD in the general population with a high cardiovascular risk, they noted.

Despite finding no statistically significant effect of severity of disease or factor level on CVD events, they stressed that this should be validated in further trials “due to the low event rate and short period of follow-up,” and suggested that a 10-year follow-up period would be more informative.

The authors advised assessment of CVD risk factors and risk profile for all patients as in the general population, which they said “could be the task of a comprehensive care centre, which provides lifelong treatment and care for people with haemophilia”.

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