Hemophilia is a bleeding disorder that, if untreated, causes recurrent bleeding into joints. "Vigorous physical activity is thought to increase risk of bleeds in children with hemophilia, but the magnitude of the risk is unknown," according to background information in the article. Information about risks associated with physical activity is needed to help inform decisions regarding participation in physical activity, the authors write.
Carolyn R. Broderick, M.B.B.S., of the University of Sydney, Australia and colleagues conducted a study to quantify the transient (short duration) increase in risk of bleeding associated with vigorous physical activity in children with hemophilia. The study was conducted at three pediatric hemophilia centers in Australia between July 2008 and October 2010 and included 104 children and adolescent boys ages 4 through 18 years with moderate or severe hemophilia A or B who were monitored for bleeds for up to 1 year. Following each bleed, the child or parent was interviewed to determine exposures to physical activity preceding the bleed. Physical activity was categorized according to expected frequency and severity of collisions. The risk of bleeds associated with physical activity was estimated by contrasting exposure to physical activity in the 8 hours before the bleed with exposures in two 8-hour control (non-bleed) windows, controlling for levels of clotting factor in the blood. The median (midpoint) duration of follow-up was 52 weeks.