Hemophilia: Contact Sports Pose Little Risk

Emma Hitt, PhD

October 09, 2012

October 9, 2012 — Vigorous physical activity in 4- to 18-year-old boys with moderate or severe hemophilia appears to be associated with a transiently increased risk for bleeding, although the absolute risk is low and prophylactic treatment can help reduce it further, according to new research.

Carolyn R. Broderick, MBBS, from the Sydney Medical School and University of Sydney in Australia, and colleagues report their findings in the October 10 issue of JAMA.

According to the researchers, previous investigations have not found an association between the level of physical activity and risk for bleeding in children with hemophilia. This study looks more closely at the degree of risk elevation of bleeding with vigorous physical activity in particular. "The primary aim of this study was to quantify the transient increase in risk of bleeding associated with vigorous physical activity in children with hemophilia," the authors write. "Secondary aims were to determine the induction period for a bleed caused by vigorous physical activity (ie, the time between physical activity and appearance of a bleed) and to determine the association between clotting factor level and risk of bleeds." The researchers state that their findings will help to "inform decisions about participation in physical activity and to optimize prophylactic schedules."

Dr. Broderick and colleagues designed a case-crossover study nested within a prospective cohort study and recruited boys with moderate or severe hemophilia A or B (standard severity designation based on factor VIII - IX levels ≤5% of normal). Physical activity was defined by American National Hemophilia Foundation categories on the basis of the "expected frequency and severity of collisions," such that no collisions were expected in category 1 (eg, swimming), collisions might occur in category 2 (eg, basketball), and collisions are sure to occur in category 3 (eg, wrestling).

The researchers ultimately recruited 104 boys with 336 bleeds and the equivalent of 4839 person-weeks. They closely evaluated the pattern of bleeds, exposure to physical activity, estimates of factor levels, and timing of the bleeds.

The bleeds associated with physical activity were noted within 1 hour of activity. The researchers found that participation in category 3 activity was associated with greater transient risk (odds ratio [OR], 3.7 [95% confidence interval [CI], 2.3 - 7.3] for category 3 vs category 1; P < .001) than participation in category 2 physical activity (OR, 2.7 [95% CI, 1.7 - 4.8] for category 2 vs category 1; P < .001).

The researchers also found that clotting factor levels of around 50% reduced risk for bleeds to below the risk experienced during periods of inactivity with no exogenous clotting factor. Specifically, bleeding incidence was lower by 2% (95% CI, 1% - 3%; P = .004) for every 1% increase in clotting factor level.

As noted by the authors, the implications of these findings are that risk reduction from prophylactic administration of clotting factor outweighs the relative risk of participation in collision sports.

Questions Remain

In an accompanying editorial, Marilyn J. Manco-Johnson, MD, from the Department of Pediatrics, Hemophilia and Thrombosis Center, University of Colorado and Children's Hospital Colorado in Aurora, points out that "[h]emophilia almost exclusively affects males and peer participation of boys in many societies is centered around competitive sports."

She adds that "observations [from this study] offer the opportunity to further minimize bleeding risks of participation without increasing factor utilization or cost."

Dr. Manco-Johnson recommends a tailored schedule of prophylactic factor administration based on physical activity, such that the risk for injury in a child with hemophilia approaches that of a normal child.

In an independent comment, Erik Berntop, MD, PhD, from Lund University in Sweden, noted that the findings support the idea that children with hemophilia receiving prophylaxis can engage in physical activity. "The major addition is that this now has been shown in a scientifically sound study," he told Medscape Medical News.

Dr. Berntop also noted that remaining unanswered questions include, "What number of extra bleeds per year is dangerous long term for development of arthropathy?" and "What trough levels of clotting factors can be acceptable for prophylaxis?"

"Children with hemophilia can do sports," he emphasized. "This is very important for their development, both physically and mentally." He said that clinicians should encourage physical activity and tailor prophylaxis accordingly, although he added that "very vigorous contact/collision sports should be avoided if possible."

This study was funded by the Australian National Health and Medical Research Council. Dr. Broderick and several other study authors reported that they have previously received a competitive research grant from the Bayer Hemophilia Awards Program and other commercial interests including various financial relationships with NovoNordisk, Baxter Health Care, CSL Behring, and/or Pfizer. Dr. Manco-Johnson states that she has received honoraria for advisory board participation from Baxter BioScience, Bayer Health-Care, CSL Behring, NovoNordisk, and Octapharma and has received research funding from Bayer HealthCare and CSL Behring. Dr. Berntop has disclosed no relevant financial relationships.

JAMA. 2012;308:1452-1459.