Clinical Outcome Following Concussion Among College Athletes with a History of Prior Concussion: A Systematic Review

Sports Medicine - Open

Table 2 The Newcastle–Ottawa Quality Assessment Scale scores and the level of evidence of the included studies (listed alphabetically)

First author (year)	Design^a	Newcastle–Ottawa Scale^b				CEBM
First author (year)	Design^a	Selection (0–4)	Comparability (0–2)	Outcome/exposure (0–3)	Total credits	Level of evidence (1–5)
Asken et al. [26]	Cohort	★★☆★	☆☆	★★☆	5	3
Bretzin et al. [33]	Cohort	★★☆★	★☆	★★☆	6	3
Bruce and Echemendia [22]	Cohort	★★☆★	☆☆	☆★☆	4	4
Churchill et al. [27]	Cohort	★★☆★	★☆	☆★☆	5	3
Gallagher et al. [28]	Cohort	★★★★	☆☆	★★☆	6	3
Guskiewicz et al. [23]	Cohort	☆★☆★	☆☆	★★★	5	3
Howell et al. [35]	Cohort	★★☆★	☆☆	★★☆	5	3
Lempke et al. [29]	Cohort	★★★★	★★	★★★	9	4
Meehan et al. [20]	Cohort	☆★☆★	☆☆	☆★★	4	3
Mihalik et al. [24]	Cohort	☆★☆★	☆☆	★★☆	4	3
Pattinson et al. [32]	Cohort	★★☆★	☆☆	★★★	6	3
Putukian et al. [30]	Cohort	★★☆★	☆☆	☆★★	5	3
Slobounov et al. [21]	Cohort	☆★★★	☆☆	★★★	6	2
Vargas et al. [31]	Case–Control	★★★☆	☆☆	☆☆☆	3	4
Wasserman et al. [3]	Cohort	★★★☆	☆☆	★★★	6	3
Zuckerman et al. [2]	Cohort	★★★☆	★★	☆★★	7	3

CEBM = Centre for Evidence-Based Medicine
^aFor the NOS, we determined the study design in reference to the determination of whether prior concussion history is a predictor of worse clinical outcome
^bWhen completing the NOS, we rated the study in relation to whether prior concussion history is a predictor of worse clinical recovery from concussion. Thus, in certain circumstances, the original study design might have earned credit on one of the NOS parameters based on the predictor variables of interest in that study (which were not prior concussion history). However, when we conceptualized the study with prior concussion history as the primary variable of interest, it did not receive credit on that same parameter (e.g., because appropriate covariates of prior concussion history were not examined)