Table 1

Characteristics of studies included

Author	Year	Country	Sample size	Average age (years)	Sport type	Study design	Risk of bias*
Aizer et al	2009	America	8448	52	Mixed and Endurance†	Cohort	2
Andersen et al	2013	Sweden	52 755	57	Nordic Skiing	Cohort	2
Baldesberger et al	2008	Switzerland	124	67	Cycling	Cohort	2
Calvo et al	2016	Spain	172	46	Mixed and Endurance‡	Case–control	1
Claessen et al	2011	Belgium	156	52	Mixed and Endurance§	Case–control	2
Elosua et al	2006	Spain	160	43	Mixed and Endurance¶	Case–control	1
Karjalainen et al	1998	Finland	440	46	Orienteering	Cohort	1
Molina et al	2008	Spain	473	39	Running	Cohort	1
Mont et al	2002	Spain	216	44	Mixed and Endurance**	Case–control	2
Myrstad et al	2014	Norway	2376	69	Nordic Skiing	Cohort	2
Myrstad et al	2016	Norway	4952	69	Nordic Skiing	Cohort	2
Schreiner et al	2016	America	149	72	Swimming	Case–control	3
Van Buuren et al	2012	Germany	57	57	Handball	Case–control	2

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.