Table 1

Characteristics of studies included

AuthorYearCountrySample sizeAverage age (years)Sport typeStudy designRisk of bias*
Aizer et al 2009America844852Mixed and Endurance†Cohort2
Andersen et al 2013Sweden52 75557Nordic SkiingCohort2
Baldesberger et al 2008Switzerland12467CyclingCohort2
Calvo et al 2016Spain17246Mixed and Endurance‡Case–control1
Claessen et al 2011Belgium15652Mixed and Endurance§Case–control2
Elosua et al 2006Spain16043Mixed and Endurance¶Case–control1
Karjalainen et al 1998Finland44046OrienteeringCohort1
Molina et al 2008Spain47339RunningCohort1
Mont et al 2002Spain21644Mixed and Endurance**Case–control2
Myrstad et al 2014Norway237669Nordic SkiingCohort2
Myrstad et al 2016Norway495269Nordic SkiingCohort2
Schreiner et al 2016America14972SwimmingCase–control3
Van Buuren et al 2012Germany5757HandballCase–control2
  • References are available in the supplemental file.

  • *Risk of bias: 1=low, 2=moderately low, 3=moderately high, 4=high. See online supplemental file 1 for full references.

  • †Cycling, racquet sports and swimming.

  • ‡Cycling, gym, marathon running, swimming, team sports, trekking and other.

  • §Basketball, cycling, diving, handball, horse riding, running, soccer, tennis, triathlon.

  • ¶Unknown sports.

  • **Athletics, cycling, running, soccer, swimming, weight lifting.