title: Estimation of transient increases in bleeding risk associated with physical activity in children with haemophilia.
abstract: BACKGROUND
  Although it is widely appreciated that vigorous physical activity can increase the risk of bleeding episodes in children with haemophilia, the magnitude of the increase in risk is not known. Accurate risk estimates could inform decisions made by children with haemophilia and their parents about participation in physical activity and aid the development of optimal prophylactic schedules. The aim of this study is to provide an accurate estimate of the risks of bleeding associated with vigorous physical activity in children with haemophilia.
  
  
  METHODS
  The study will be a case-crossover study nested within a prospective cohort study. Children with moderate or severe haemophilia A or B, recruited from two paediatric haematology departments in Australia, will participate in the study. The child, or the child's parent or guardian, will report bleeding episodes experienced over a 12-month period. Following a bleeding episode, the participant will be interviewed by telephone about exposures to physical activity in the case period (8 hours before the bleed) and 2 control periods (an 8 hour period at the same time on the day preceding the bleed and an 8 hour period two days preceding the bleed). Conditional logistic regression will be used to estimate the risk of participating in vigorous physical activity from measures of exposure to physical activity in the case and control periods.
  
  
  CONCLUSIONS
  This case-control study will provide estimates of the risk of participation in vigorous physical activity in children with haemophilia.
authors.affiliation: School of Medical Sciences, University of New South Wales, Randwick NSW 2052, Australia. c.broderick@unsw.edu.au
authors.forename: Carolyn R
authors.initials: CR
authors.lastname: Broderick
authors.forename: Robert D
authors.initials: RD
authors.lastname: Herbert
authors.forename: Jane
authors.initials: J
authors.lastname: Latimer
authors.forename: Chris
authors.initials: C
authors.lastname: Barnes
authors.forename: Julie A
authors.initials: JA
authors.lastname: Curtin
authors.forename: Paul
authors.initials: P
authors.lastname: Monagle