eTable 4. Quality assessment of studies on analgesic use in professional and elite sport (data collection based on doping control forms).

Study (reference)	Selection	Comparability	Outcome	Total (max. 9)
Corrigan and Kazlauskaz (2003) (26)	****	*	**	7
Kavukcu and Burgazli (2013) (36)	****	*	**	7
Oester et al. (2019) (e4)	****	*	**	7
Pedrinelli et al. (2015) (e6)	****	*	**	7
Trinks et al. (2021) (e14)	****	**	**	8
Tscholl et al. (2008) (e15)	****	*	**	7
Tscholl et al. (2009) (9)	****	**	**	8
Tscholl et al. (2010) (e16)	****	**	**	8
Tscholl and Dvorak (2012) (e19)	****	*	**	7
Tsitsimpikou et al. (2009) (e20)	****	*	**	7
van Thuyne et al. (2008) (e21)	****	*	**	7
Vaso et al. (2015) (10)	****	**	**	8

Newcastle Ottawa Scale (NOS) for evaluating cohort studies:

The individual studies are scored for selection (representativeness of the exposed cohort and selection of the non-exposed cohort; ascertainment of exposure; demonstration that outcome of interest was not present at start of study), comparability, and recording of exposure/endpoint (validity of the data provided [outcome], endpoint within a sufficient observation period, consideration of and control for missing data).

Where the risk of bias is low, one star is given; the maximum possible number of stars is nine (16).