Patients with hemophilia A are at higher risk of bleeding when they participate in high-collision physical activity, according to research published in the Journal of Blood Medicine.

The prospective Study of Prophylaxis, ACtivity and Effectiveness (SPACE) included 54 patients without FVIII inhibitors receiving antihemophilic factor (recombinant) (rAHF). The study evaluated the effect of physical activity and timing of rAHF infusion on bleeding risk.

All patients had severe or moderately severe hemophilia A. They tracked activity and treatment with an eDiary app and a wearable activity tracker for 6 months. Participants ranged in age from 11 to 58 years.

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Most patients reported administering infusion before physical activity. Nearly 65% of patients infused more than 24 hours before starting physical activity.

A total of 31.5% (17/54) of patients reported no bleeding episodes during the 6-month period. The remaining 37 patients reported a total of 185 bleeding episodes, with a mean of 3.43 bleeds per person. A mean of 1.39 bleeds per person were related to physical activity.

Patients receiving prophylaxis (n=31) reported a mean of 1.26 bleeds related to activity, and patients receiving on-demand treatment (n=6) reported a mean of 2.29 bleeds as activity-related.

Based on the eDiary entries, the risk of bleeding tended to increase with higher risk physical activity. Infusion timing was not correlated with activity-related bleeding risk.

Patients self-reported whether bleeds were spontaneous or activity-related, and some patients may have had difficulty distinguishing between the two. About one-third of participants were more than 60% compliant with entering data in the eDiary and activity tracker, which limits the results.

Overall, time since rAHF infusion was not related to bleeding risk, but the risk of bleeds increased with more intense physical activity.

Disclosure: Some study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.


Konkle BA, Quon DV, Raffini L, et al. A prospective observational study of antihemophilic factor (recombinant) prophylaxis related to physical activity levels in patients with hemophilia A in the United States (SPACE). J Blood Med. 2021;12:883-896. doi:10.2147/JBM.S327180