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

Sports Medicine - Open

Table 1 Summary of the study outcomes (studies listed alphabetically)

First author (year)	Total N	Prior concussion n		Concussion history coding	Prior concussion during study	Concussion history is study focus	Symptom duration			Time to return to play			Other outcomes
							Significant			Significant			Significant
							Findings			Findings			Findings
		f	%				Yes	No	Direction	Yes	No	Direction	Yes	No	Direction
Asken et al. [26]	97	48	49.5%	0, 1, ≥ 2	No	No					X	–
Bretzin et al. [33]	1,974	1,030	52.2%	0, 1, 2, ≥ 3	NR	No		X	–		X	–	X^a	X	Worse and Null
Bruce and Echemendia [22]	57	30	52.6%	≥ 1 Prior	No	Yes	X		Worse
Churchill et al. [27]	33	19	57.6%	≥ 1 Prior	No	No		X	–
Gallagher et al. [28]	90	34	37.8%	≥ 1 Prior	No	No		X	–
Guskiewicz et al. [23]	184	66^b	NR	0, 1, 2, ≥ 3	Yes	Yes	X		Worse
Howell et al. [35]	94	60	63.8%	≥ 1 Prior	NR	No								X^c	^–
Lempke et al. [29]	187	86	46.0%	≥ 1 Prior	No	No	± X ±	X	Worse and Null	± X ±	X	Worse and Null
Meehan et al. [20]	64	30	46.9%	≥ 1 Prior	No	No		X	–
Mihalik et al. [24]	45	19	37.8%	0, 1, ≥ 2	Yes & No	No		X	–	X		Worse
Pattinson et al. [32]	127	54	42.5%	0, 1, 2, ≥ 3	NR	No		X	–
Putukian et al. [30]	138	64	46.4%	0, 1, ≥ 2	No	No		X	–		X	–
Slobounov et al. [21]	160	9	5.6%	0, 1	Yes	Yes		X	–		X	–	X^c	X^d	Worse and Null
Vargas et al. [31]	84	NR	NR	Continuous	No	No								X^e	–
Wasserman et al. [3]	1,670^f	151^f	9.0%	≥ 1 Prior	Yes	No	X		Worse	X		Worse
Zuckerman et al. [2]	1,507	210	13.9%	≥ 1 Prior	Yes	No	X		Worse

^aTime to return to academics; prior concussion associated with longer time to return in men but not in women
^bThis figure reflects the total number of prior concussions, not the number of participants with prior concussions
^cVestibular functioning
^dCognitive functioning
^eDepressive symptoms
^fThis study reported number of concussions and not the number of participants who sustained a concussion
± X ± This study reported that concussion history was not associated with symptom duration or time to return to play. However, among athletes who sustained concussions during away competitions (versus at home), concussion history was associated with longer symptom duration and time to return to play. Therefore, for the purpose of this review, in tabulating the number of “positive” studies, we did not count this one as a positive study (e.g., in Table 3). “Prior Concussion During Study” refers to whether concussion history was assessed in the study based on concussions sustained before the study (“No”), during the study (“Yes”), both before and during the study (“Yes & No”), or was not reported (“NR”)