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Abstract

The purpose of this study was to examine the relationship between sleep duration and clinical concussion assessments across concussion management timepoints in service academy cadets and midshipmen. An observational cohort study was conducted at four military service academies participating in the Concussion Assessment, Research and Education Consortium from 2014–2020. Demographic information (site, academic year, varsity status, sex, and concussion history) and pre-injury baseline assessments were collected at the time of enrollment. Participants who sustained a concussion underwent standardized evaluations at three follow-up timepoints [initial, graduated return to activity protocol initiation (GRTA), unrestricted return to activity (URTA)]. The Sport Concussion Assessment Tool was used to assess concussion symptom burden, cognitive function and balance and the Brief Symptom Inventory-18 was used to assess psychological distress at each timepoint. Self-reported hours slept was recorded during each evaluation. Univariate and multiple linear regression models were used to examine the relationship between sleep duration and clinical assessments. Kruskal-Wallis models were used to evaluate differences in clinical assessment outcomes by hours slept. During the study period, 17,194 participants (25% female;19.01 ± 1.41y) completed a baseline assessment and 1,534 (39% female;20.02 ± 1.49y) sustained a concussion. Linear regression models revealed sleep duration was associated with symptom severity scores across all evaluation timepoints: baseline (Coefficient = −2.22; 95% CI = −2.36, −2.07; p = <0.001), initial (Coefficient = −2.64; 95% CI = −3.27, −2.00; p = <0.001), GRTA (Coefficient = −0.30; 95% CI = −0.40, −0.20; p = <0.001), and URTA (Coefficient = −0.14; 95% CI = −0.19, −0.09; p = <0.001). Similar results were observed for psychological distress, balance and cognitive assessments with increased sleep associated with improved outcomes. Increased sleep may be associated with improved clinical assessment outcomes and should be considered when evaluating these assessments.

Introduction

Concussions are common in military service members and National Collegiate Athletics Association (NCAA) athletes. From January 2000 to May 2024, 505,896 concussions were recorded by the Department of Defense (DoD)¹ and from 2009 to 2014, an estimated 10,560 occurred among NCAA athletes.² Various entities have established recommendations for concussion management which include conducting baseline evaluations when resources allow and postinjury evaluations throughout a recovery trajectory.^3–5 Substantial research is available reporting the effectiveness of different clinical assessments of concussion^6–9 and the impact that numerous factors have on these tests.^10,11 One factor recently studied more scrupulously is sleep deprivation.

Sleep is imperative to different systemic functions and plays a vital role in general health and well-being.¹² The minimum amount recommended for people aged 18–64 is 7–9 h.¹³ Specific settings can make it challenging to meet these sleep recommendations. Sleep deprivation is prevalent among college students and military service members due to the demands of training and the developmental needs of this age group.^14–16 In a military service academy (MSA) setting, cadets obtained an average of less than 5.5 h of sleep during the school year and 69–72% of deployed US service members previously reported less than 6 h of nightly sleep.^15,16 Decreased sleep can impact neurobehavioral and cognitive performance, metabolite clearance, nociception, and mood regulation.¹²

Due to the known negative effects of decreased sleep on neurocognitive performance, the impact of sleep duration on concussion management has been the focus of substantial research.^17–19 Healthy individuals reporting poor sleep have endorsed symptom burdens during concussion baseline testing similar to those having sustained a concussion¹⁷ and sleep deficits reported postconcussion have been associated with increased symptom burdens and decreased neurocognitive testing outcomes.¹⁹ Whether these sleep deficits are from the pathology of concussions or external factors, there appears to be some association between sleep and clinical concussion assessments.²⁰ A dearth of research is available, however, examining the impact of sleep duration on clinical concussion assessments used in a military training environment.

Therefore, the purpose of this study was to examine the relationship between sleep duration and specific clinical assessments used in concussion management at baseline and specific postconcussion timepoints with MSA cadets and midshipmen. We hypothesized decreased sleep duration would be associated with increased endorsement of concussion symptoms and psychological distress and decreased performance on balance and cognitive assessments at each evaluation timepoint.

Methods

Design and setting

An observational cohort study was conducted among cadets and midshipmen enrolled at four US MSAs participating in the Concussion Assessment, Research, and Education (CARE) Consortium from 2014 to 2020 to examine the association between sleep duration and clinical concussion assessments collected at baseline and postconcussion. All study procedures were reviewed and approved by the Institutional Review Board at each site and the US Army Human Research Protection Office. Informed consent was obtained prior to baseline testing.

Procedures

The CARE Consortium methodology has been described previously.^21,22 The following summarizes procedures pertinent to the current analysis. During the first semester at their respective academy, participants underwent baseline concussion testing and reported demographic and medical information including height, weight, MSA site, varsity status (non-NCAA athlete, NCAA athlete), sex (male, female), and concussion history (0 or ≥1 previous concussion). The baseline testing date was assessed to account for the potential impact of cadet basic training (CBT) on clinical concussion assessments.²³ Generally, CBT is conducted for seven weeks in July and August preceding the academic year. Participants were dichotomized (baseline testing during CBT, baseline testing after CBT) based on whether baseline testing was administered during CBT. Researchers at each MSA confirmed CBT dates.

Participants who sustained a concussion underwent standardized evaluations at three timepoints: within 48 h postconcussion (<48), upon initiation of a graduated return to activity (GRTA) protocol, and when cleared for unrestricted return to activity (URTA). The GRTA protocol initiation evaluation is a non-fixed timepoint performed at the treating clinician’s discretion, based on the readiness of their patient to begin a GRTA protocol, and has been referred to as the “asymptomatic” timepoint.²⁴ At baseline and each postconcussion evaluation, the Sport Concussion Assessment Tool, third edition (SCAT-3) symptom checklist, Brief Symptom Inventory-18 (BSI-18), Standardized Assessment of Concussion (SAC), and Balance Error Scoring System (BESS) were administered. Self-reported hours slept were obtained from a question added to the end of the SCAT-3 symptom checklist. All demographic information and clinical measures were documented by each site into a centralized computer database (QuesGen Systems Inc.; Burlingame, CA, USA).

This study only analyzed each participant’s initial baseline evaluation. Baseline and postconcussion evaluations were excluded if the participant did not report hours slept. To control for extraneous factors that may have impacted postconcussion evaluations, this study only analyzed the first incident concussion sustained by participants during the follow-up period. Cases designated as complicated recoveries by clinicians were also excluded.

Injury definition and surveillance

Concussion was operationally defined as “a change in brain function following a force to the head, which may be accompanied by temporary loss of consciousness, but is identified in awake individuals with measures of neurological and cognitive dysfunction”²⁵ and diagnosed by clinicians.

Instruments

Sport Concussion Assessment Tool, Third Edition

The SCAT-3 includes a concussion symptom checklist that measures 22 symptoms on a 0 (no symptoms) to 6 (severe symptoms) Likert scale.⁷ The number of symptoms reported with a score greater than 0 are tallied to determine a total symptom score (range: 0–22) and each Likert scale value is summed to determine a symptom severity score (range: 0–132).⁷ This symptom scale has displayed a sensitivity of 47.4 − 72.2% and specificity of 78.6 − 91.7% in concussion diagnosis.²⁶

Brief Symptom Inventory-18

The BSI-18 measures psychological distress. It provides subscores of anxiety, somatization, and depression and a total score (global severity index [GSI]).⁶ Each item is scored on a 0 (not at all) to 4 (extremely) Likert scale with higher scores indicating increased psychological distress.²⁷ The GSI (α = 0.93) has displayed good internal consistency²⁷ and significant correlations with psychological distress measures in TBI patients.⁶

Standardized Assessment of Concussion

The SAC is a cognitive assessment providing a total score (range: 0–30) of orientation, immediate and delayed memory, and concentration with lower scores indicating cognitive impairment.⁷ The SAC has demonstrated a sensitivity of 0 − 94%^7,8 and specificity of 91.7 − 100%⁷ in concussion diagnosis.

Balance Error Scoring System

The BESS is widely used in concussion management to assess balance.⁹ The test consists of three standardized stances, each performed on firm and unstable surfaces. Subjects hold each stance for 20 s and balance errors during the test are totaled with higher totals indicating worse balance.⁸ The BESS has displayed a sensitivity of 16 − 60% to concussion diagnosis in acute settings.⁹

Statistical analysis

Descriptive statistics were calculated for hours slept for the entire cohort and four sleep groups of <5, ≥5 to <6, ≥6 to <7, and ≥7 h slept were established. Additional descriptive statistics were calculated for each covariate (sex, varsity status, academic year, concussion history, baseline testing date) and clinical assessment (SCAT-3 symptom severity, BSI-18 GSI, SAC total, BESS total). All statistical analyses were conducted on each timepoint separately. Sleep outliers were calculated using Tukey’s method²⁸ and removed. Univariate linear regression models were used to examine the relationship between sleep duration and clinical assessment outcomes at each timepoint.^18,19,29,30 Univariate models were also conducted to assess the association between covariates (sex, academic year, varsity status, concussion history, baseline testing date) and clinical assessment outcomes at each timepoint.^10,29,31 Multivariable models were then used to assess the association between sleep and clinical assessment outcomes while controlling for significant covariates identified in the univariate models. A subject missing any given clinical measure was omitted from that specific statistical model. Coefficients and 95% confidence intervals were calculated for all regression models with larger coefficients indicative of larger incremental changes in the clinical measure being assessed. Kruskall–Wallis tests were conducted to determine whether a significant difference was present for each clinical measure between the different sleep groups within each timepoint. Post hoc Mann–Whitney U testing with a Bonferonni correction was conducted on statistically significant Kruskall–Wallis models to identify group differences. Friedman’s analysis of variance (ANOVA) models were conducted to determine whether within-subject differences existed for each clinical measure across the four timepoints. Statistical significance was set at α < 0.05 for all models and α < 0.017 for Mann–Whitney U models. All statistical analyses were conducted in StataSE (StataCorp, College Station, TX) except for Friedman’s ANOVA testing (SPSS; IBM, Armonk, NY).

Results

During the study period, 17,194 participants completed a baseline assessment and 1,787 sustained a concussion and completed follow-up assessments. Table 1 displays baseline and postinjury demographic information. Injured subjects took 12.65 ± 14.11 days and 24.38 ± 21.68 days to reach the asymptomatic and URTA timepoints, respectively. Figure 1 outlines study enrollment. Friedman’s ANOVA testing revealed significant within-subject differences in SCAT-3 symptom severity (χ² = 14,402.59, p < 0.001), BSI-18 GSI (χ² = 13,644.69, p < 0.001), SAC total scores (χ² = 39,175.64, p < 0.001), and BESS total scores (χ² = 38,504.50, p < 0.001) across evaluation timepoints.

FIG. 1.

Study enrollment diagram.

Table 1.

Demographic and Covariate Descriptive Statistics for Baseline and Injured Groups

	Baseline	Injured
n	17,194	1,534^a
Demographics	(Mean ± SD)
Height, cm	176.46 ± 12.07	175.09 ± 14.36
Mass, kg	75.03 ± 13.52	74.07 ± 15.07
Age, years	19.01 ± 1.41	20.02 ± 1.49
Covariates (% of specified covariate)
Academic year
1st year	17,194 (100%)	991 (64%)
2nd year	—	308 (21%)
3rd year	—	178 (11%)
4th year	—	56 (3%)
5th year	—	1 (<1%)
Sex
Male	12,877 (75%)	939 (61%)
Female	4,317 (25%)	595 (39%)
Varsity status
NCAA athlete	5,460 (32%)	599 (39%)
Non-NCAA athlete	11,734 (68%)	935 (61%)
Concussion history^b
No history	13,941 (81%)	1,119 (73%)
≥1 previous concussion	3,113 (18%)	400 (26%)
Baseline during CBT
Occurred during training	7,825 (46%)	—
Occurred after training	9,369 (54%)	—

This value is based on the number of initial injury evaluation analyzed during this study.

143 participants did not provide concussion history at baseline, 15 of those participants sustained a concussion.

CBT, Cadet Basic Training; NCAA, National Collegiate Athletics Association; SD, standard deviation.

Impact of sleep on concussion clinical assessments

Kruskall–Wallis models indicated sleep had a significant association with select concussion assessments (Tables 2 and 3). Decreased SCAT-3 symptom severity was observed in participants reporting increased sleep across all timepoints. Sleep demonstrated a significant association with SAC assessments at the <48 and asymptomatic timepoints and BSI-18 GSI and BESS total scores at the baseline and <48 timepoints. Increased sleep was associated with better performance on all assessments.

Table 2.

Concussion Symptom Severity and Psychological Distress Total Scores by Timepoint and Hours Slept

					Post hoc results
Hours slept	n	Mean ± SD	χ²	p ^a	Group	z-score	p ^b
SCAT-3 symptom severity
Baseline
<5 (1)	2,042	12.23 ± 15.85	1,102.54	<0.001	1 vs. 2	4.519	<0.001
≥5 to <6 (2)	4,788	10.02 ± 13.35			1 vs. 3	13.051	<0.001
≥6 to <7 (3)	6,036	7.33 ± 10.68			1 vs. 4	26.295	<0.001
≥7 (4)	4,328	4.15 ± 7.80
<48 h Postinjury
<5 (1)	140	38.60 ± 23.60	63.71	<0.001	1 vs. 2	3.088	0.002
≥5 to <6 (2)	198	30.87 ± 20.91			1 vs. 3	4.203	<0.001
≥6 to <7 (3)	402	29.00 ± 20.04			1 vs. 4	6.973	<0.001
≥7 (4)	794	24.63 ± 19.89
Graduated return to activity protocol initiation
<5 (1)	65	2.82 ± 4.75	29.86	<0.001	1 vs. 2	1.325	0.185
≥5 to <6 (2)	151	1.80 ± 3.10			1 vs. 3	2.751	0.006
≥6 to <7 (3)	409	1.31 ± 2.83			1 vs. 4	4.105	<0.001
≥7 (4)	855	0.93 ± 2.12
Unrestricted return to activity
<5 (1)	99	0.71 ± 2.40	33.91	<0.001	1 vs. 2	1.116	0.264
≥5 to <6 (2)	201	0.51 ± 1.46			1 vs. 3	3.119	0.002
≥6 to <7 (3)	512	0.29 ± 1.27			1 vs. 4	5.164	<0.001
≥7 (4)	744	0.16 ± 0.76
BSI-18 global severity index
Baseline
<5 (1)	2,006	4.58 ± 7.70	322.79	<0.001	1 vs. 2	2.228	0.026
≥5 to <6 (2)	4,707	3.73 ± 6.31			1 vs. 3	6.991	<0.001
≥6 to <7 (3)	5,934	3.05 ± 5.49			1 vs. 4	14.240	<0.001
≥7 (4)	4,297	2.19 ± 4.85
<48 h postinjury
<5 (1)	112	8.86 ± 7.72	41.52	<0.001	1 vs. 2	1.762	0.078
≥5 to <6 (2)	157	7.80 ± 8.60			1 vs. 3	3.450	0.001
≥6 to <7 (3)	313	6.15 ± 6.51			1 vs. 4	5.581	<0.001
≥7 (4)	677	4.98 ± 5.76
Graduated return to activity protocol initiation
<5 (1)	57	2.14 ± 4.52	7.49	0.058
≥5 to <6 (2)	134	1.84 ± 3.52
≥6 to <7 (3)	372	1.31 ± 3.26
≥7 (4)	828	1.03 ± 2.16
Unrestricted return to activity
<5 (1)	88	0.98 ± 2.52	6.96	0.073
≥5 to <6 (2)	171	0.60 ± 1.80
≥6 to <7 (3)	476	0.59 ± 2.53
≥7 (4)	699	0.35 ± 1.17

α < 0.05.

α < 0.017 after a Bonferroni correction.

BSI-18, Brief Symptom Inventory-18; SCAT-3, Sport Concussion Assessment Tool, 3rd edition; SD, standard deviation.

Table 3.

Standardized Assessment of Concussion and Balance Error Scoring System Total Scores by Timepoint and Hours Slept

					Post hoc results
Hours slept	n	Mean ± SD	χ²	p^a value	Group	z-score	p^b value
Standardized Assessment of Concussion
Baseline
<5 (1)	2,015	27.66 ± 1.75	5.11	0.164
≥5 to <6 (2)	4,714	27.71 ± 1.80
≥6 to <7 (3)	5,871	27.73 ± 1.79
≥7 (4)	4,158	27.64 ± 1.90
<48 h postinjury
<5 (1)	136	26.26 ± 2.83	25.43	<0.001	1 vs. 2	−2.448	0.014
≥5 to <6 (2)	192	26.98 ± 2.30			1 vs. 3	−3.420	0.001
≥6 to <7 (3)	388	27.11 ± 2.16			1 vs. 4	−4.774	<0.001
≥7 (4)	755	27.34 ± 2.21
Graduated return to activity protocol initiation
<5 (1)	59	27.85 ± 1.83	10.33	0.016	1 vs. 2	−1.349	0.177
≥5 to <6 (2)	143	28.23 ± 1.64			1 vs. 3	−2.242	0.025
≥6 to <7 (3)	395	28.39 ± 1.59			1 vs. 4	−2.774	0.006
≥7 (4)	842	28.50 ± 1.50
Unrestricted return to activity
<5 (1)	98	28.60 ± 1.60	0.71	0.872
≥5 to <6 (2)	199	28.64 ± 1.57
≥6 to <7 (3)	506	28.66 ± 1.49
≥7 (4)	736	28.74 ± 1.42
Balance Error Scoring System
Baseline
<5 (1)	1,991	15.37 ± 6.80	26.15	<0.001	1 vs. 2	1.676	0.094
≥5 to <6 (2)	4,664	15.08 ± 6.72			1 vs. 3	2.192	0.028
≥6 to <7 (3)	5,824	14.97 ± 6.67			1 vs. 4	4.606	<0.001
≥7 (4)	4,138	14.60 ± 6.80
<48 h postinjury
<5 (1)	128	20.16 ± 9.92	8.30	0.040	1 vs. 2	2.383	0.017
≥5 to <6 (2)	183	17.60 ± 8.42			1 vs. 3	1.828	0.068
≥6 to <7 (3)	370	18.33 ± 7.83			1 vs. 4	2.572	0.010
≥7 (4)	748	18.04 ± 8.44
Graduated return to activity protocol initiation
<5 (1)	61	13.33 ± 5.84	2.15	0.543
≥5 to <6 (2)	141	12.81 ± 5.38
≥6 to <7 (3)	393	13.13 ± 5.80
≥7 (4)	834	13.40 ± 5.75
Unrestricted return to activity
<5 (1)	98	12.50 ± 5.49	4.33	0.228
≥5 to <6 (2)	198	11.86 ± 5.34
≥6 to <7 (3)	503	12.60 ± 5.72
≥7 (4)	721	12.42 ± 4.88

α < 0.05.

α < 0.017 after a Bonferroni correction.

SD, standard deviation.

Univariate linear regression model results (Table 4) revealed a significant association between both SCAT-3 symptom severity and BSI-18 GSI and sleep at all four timepoints with decreased sleep being associated with increased symptom burdens. The coefficients suggest the magnitude of this association was greatest at the baseline and <48 h timepoints. For example, a 1-h increase in sleep reported during the baseline and <48 evaluation timepoints was associated with a decrease in SCAT-3 symptom severity of 2.2 and 2.6 points, respectively, and a decrease in SCAT-3 symptom severity of 0.3 and 0.1 points at the asymptomatic and URTA timepoints, respectively. Sleep duration demonstrated a significant association with BESS total scores at the baseline and <48 h timepoints and SAC total scores at the <48 h and asymptomatic evaluation timepoints with increased sleep being associated with improved performance on the assessments. Multivariable models (Table 5) yielded similar results. After controlling for significant covariates, hours slept maintained a significant association with SCAT-3 symptom severity and BSI-18 GSI at all four timepoints, with BESS total scores during baseline testing, and with SAC total scores at the <48 and asymptomatic timepoints. Increased sleep was associated with improved outcomes on each assessment.

Table 4.

Univariate Linear Regression Results for Clinical Assessments by Timepoint

	Baseline			<48 h postinjury			GRTA protocol initiation			URTA clearance
Variable	Coefficient	p value	95% CI	Coefficient	p value	95% CI	Coefficient	p value	95% CI	Coefficient	p value	95% CI
SCAT-3 symptom severity
Hours slept	−2.216	<0.001	−2.36, −2.07	−2.637	<0.001	−3.27, −2.00	−0.304	<0.001	−0.40, −0.20	−0.136	<0.001	−0.19, −0.09
Academic year	—	—	—	−0.497	0.433	−1.74, 0.74	0.085	0.298	−0.08, 0.25	0.005	0.896	−0.07, 0.08
Varsity	−0.562	0.004	−0.94, −0.18	3.725	0.001	1.59, 5.86	0.381	0.007	0.11, 0.66	0.100	0.114	−0.02, 0.22
Sex	3.124	<0.001	2.81, 3.62	7.382	<0.001	5.27, 9.49	0.070	0.617	−0.21, 0.35	0.093	0.139	−0.03, 0.22
Concussion history	0.099	0.674	−0.36, 0.56	−1.985	0.101	−4.36, 0.39	0.008	0.961	−0.30, 0.32	−0.101	0.155	−0.24, 0.04
BSI total	1.366	<0.001	1.34, 1.39	1.976	<0.001	1.84, 2.11	0.432	<0.001	0.39, 0.48	0.198	<0.001	0.17, 0.23
Baseline during CBT	9.613	<0.001	9.29, 9.94	—	—	—	—	—	—	—	—	—
BSI-18 GSI
Hours slept	−0.661	<0.001	−0.73, −0.59	−0.790	<0.001	−1.01, −0.57	−0.186	0.001	−0.30, −0.08	−0.121	0.003	−0.20, −0.04
Academic year	—	—	—	−0.418	0.057	−0.85, 0.01	−0.129	0.143	−0.30, 0.04	−0.089	0.126	−0.20, 0.03
Varsity	−0.451	<0.001	−0.64, −0.26	0.614	0.109	−0.14, 1.36	0.443	0.004	0.15, 0.74	0.150	0.143	−0.05, 0.35
Sex	1.792	<0.001	1.59, 2.00	1.449	<0.001	0.70, 2.20	0.353	0.021	0.05, 0.65	0.197	0.055	−0.00, 0.40
Concussion history	0.046	0.696	−0.19, 0.29	−0.629	0.144	−1.47, 0.21	−0.126	0.452	−0.46, 0.20	0.004	0.975	−0.22, 0.23
Baseline during CBT	3.817	<0.001	3.65, 3.99	—	—	—	—	—	—	—	—	—
SAC total
Hours slept	−0.005	0.662	−0.03, 0.02	0.161	<0.001	0.09, 0.23	0.093	0.003	0.03, 0.15	0.053	0.081	−0.01, 0.11
Academic year	—	—	—	0.094	0.180	−0.04, 0.23	0.013	0.783	−0.08, 0.11	0.028	0.521	−0.06, 0.12
Varsity	0.291	<0.001	0.23, 0.35	0.106	0.383	−0.13, 0.34	0.138	0.101	0.03, 0.30	0.218	0.005	0.07, 0.37
Sex	0.099	0.002	0.04, 0.16	−0.014	0.906	−0.25, 0.22	0.011	0.894	−0.15, 0.18	0.028	0.713	−0.12, 0.18
Concussion history	0.092	0.012	0.02, 0.16	−0.135	0.318	−0.40, 0.13	−0.048	0.612	−0.23, 0.14	−0.036	0.676	−0.20, 0.13
BSI total	0.007	0.006	0.00, 0.01	−0.078	<0.001	−0.10, −0.06	−0.057	<0.001	−0.09, −0.03	−0.015	0.459	−0.05, 0.02
Baseline during CBT	0.156	<0.001	0.10, 0.21	—	—	—	—	—	—	—	—	—
BESS total
Hours slept	−0.202	<0.001	−0.29, −0.12	−0.356	0.010	−0.63, −0.08	0.043	0.707	−0.18, 0.27	0.053	0.636	−0.17, 0.27
Academic year	—	—	—	−0.431	0.103	−0.95, 0.09	−0.331	0.068	−0.69, 0.02	0.027	0.863	−0.29, 0.34
Varsity	−0.394	<0.001	−0.61, −0.17	3.043	<0.001	2.16, 3.93	1.827	<0.001	1.21, 2.42	1.243	<0.001	0.70, 1.78
Sex	−0.274	0.024	−0.51, −0.04	0.862	0.060	−0.03, 1.76	−0.176	0.571	−0.79, 0.43	−0.282	0.308	−0.83, 0.26
Concussion history	−0.247	0.070	−0.51, 0.02	−0.928	0.069	−1.93, 0.07	−0.259	0.454	−0.94, 0.42	0.014	0.965	−0.59, 0.62
BSI total	0.111	<0.001	0.09, 0.13	0.265	<0.001	0.19, 0.34	0.161	0.004	0.05, 0.27	0.192	0.009	0.05, 0.34
Baseline during CBT	2.344	<0.001	2.14, 2.55	—	—	—	—	—	—	—	—	—

BESS, Balance Error Scoring System; CBT, Cadet Basic Training; CI, confidence interval GRTA, graduated return to activity; SAC, Standardized Assessment of Concussion; SCAT-3, Sport Concussion Assessment Tool, 3rd edition; BSI, Brief Symptom Inventory; URTA, unrestricted return to activity.

Table 5.

Multivariable Linear Regression Results for Hours Slept

	Baseline			<48 h postinjury			GRTA protocol initiation			URTA clearance
Variable	Coefficient	p value	95% CI	Coefficient	p value	95% CI	Coefficient	p value	95% CI	Coefficient	p value	95% CI
SCAT symptom severity
Hours slept	−1.378	<0.001	−1.49, −1.29	−1.243	<0.001	−1.81, −0.68	−0.209	<0.001	−0.30, −0.11	−0.117	<0.001	−0.17, −0.07
Academic year	—	—	—	0.728	0.181	−0.34, 1.80	0.126	0.093	−0.02, 0.27	0.037	0.307	−0.03, 0.11
Varsity	0.172	0.202	−0.09, 0.44	2.199	0.021	0.33, 4.07	0.217	0.099	−0.04, 0.47	0.067	0.297	−0.06, 0.19
Sex	0.544	<0.001	0.26, 0.83	4.211	<0.001	2.36, 6.07	−0.074	0.563	−0.33, 0.18	0.054	0.385	−0.07, 0.18
Concussion history	0.224	0.164	−0.09, 0.44	−0.942	0.376	−3.03, 1.15	0.111	0.441	−0.17, 0.39	−0.075	0.296	−0.22, 0.07
BSI total	1.192	<0.001	1.17, 1.21	1.887	<0.001	1.74, 2.03	0.433	<0.001	0.39, 0.48	0.191	<0.001	0.16, 0.22
Baseline during CBT	4.880	<0.001	4.62, 5.14	—	—	—	—	—	—	—	—	—
BSI-18 GSI
Hours slept	−0.664	<0.001	−0.73, −0.59	−0.776	<0.001	−1.00, −0.56	−0.161	0.004	−0.27, −0.05	−0.114	0.006	−0.19, −0.03
Academic year	—	—	—	−0.373	0.086	−0.80, 0.05	−0.109	0.215	−0.28, 0.06	−0.069	0.250	−0.19, 0.05
Varsity	−0.118	0.204	−0.30, 0.06	0.196	0.607	−0.55, 0.94	0.309	0.045	0.01, 0.61	0.110	0.297	−0.10, 0.32
Sex	1.452	<0.001	1.26, 1.65	1.330	<0.001	0.59, 2.07	0.269	0.075	−0.03, 0.56	0.181	0.080	−0.02, 0.38
Concussion history	0.203	0.067	−0.01, 0.42	−0.613	0.149	−1.45, 0.22	−0.098	0.564	−0.43, 0.23	0.018	0.875	−0.21, 0.25
Baseline during CBT	3.774	<0.001	3.60, 3.94	—	—	—	—	—	—	—	—	—
SAC total
Hours slept	—	—	—	0.102	0.009	0.03, 0.18	0.084	0.008	0.02, 0.15	—	—	—
Academic year	—	—	—	0.110	0.138	−0.04, 0.26	0.025	0.616	−0.07, 0.12	—	—	—
Varsity	—	—	—	0.186	0.152	−0.07, 0.44	0.214	0.014	0.04, 0.38	—	—	—
Sex	—	—	—	0.063	0.625	−0.19, 0.32	0.031	0.714	−0.14, 0.20	—	—	—
Concussion history	—	—	—	−0.208	0.152	−0.49, 0.08	−0.026	0.788	−0.21, 0.16	—	—	—
BSI total	—	—	—	−0.072	<0.001	−0.09, −0.05	−0.060	<0.001	−0.09, −0.03	—	—	—
Baseline during CBT	—	—	—	—	—	—	—	—	—	—	—	—
BESS total
Hours slept	−0.181	<0.001	−0.27, −0.10	−0.021	0.886	−0.31, 0.27	—	—	—	—	—	—
Academic year	—	—	—	−0.101	0.717	−0.65, 0.45	—	—	—	—	—	—
Varsity	−0.254	0.025	−0.48, −0.03	3.347	<0.001	2.39, 4.30	—	—	—	—	—	—
Sex	−0.520	<0.001	−0.48, −0.03	0.320	0.507	−0.63, 1.27	—	—	—	—	—	—
Concussion history	−0.205	0.128	−0.47, 0.06	−0.324	0.551	−1.39, 0.74	—	—	—	—	—	—
BSI total	0.052	<0.001	0.03, 0.07	0.256	<0.001	0.18, 0.33	—	—	—	—	—	—
Baseline during CBT	2.115	<0.001	1.90, 2.33	—	—	—	—	—	—	—	—	—

BESS, Balance Error Scoring System; BSI, Brief Symptom Inventory; CBT, Cadet Basic Training; CI, confidence interval; GRTA, graduated return to activity; SAC, standardized assessment of concussion; SCAT-3, Sport Concussion Assessment Tool, 3rd edition; URTA, unrestricted return to activity .

Impact of covariates and sleep on concussion clinical assessments

Univariate linear regression models (Table 4) revealed that specific covariates were associated with clinical assessment outcomes at different timepoints. Each covariate except concussion history impacted clinical measures at baseline testing. Academic year and concussion history showed no association with clinical measures at any postconcussion evaluation timepoint. Varsity cadets endorsed increased SCAT-3 symptom severity and BSI-18 GSI at baseline and decreased symptom severity and GSI at certain postconcussion timepoints. Varsity cadets also displayed lower SAC total scores at baseline and URTA clearance timepoints, increased BESS total scores during baseline testing and decreased BESS total scores at each postinjury timepoint. Females displayed increased SCAT-3 symptom severity, BSI-18 GSI, and SAC total scores and decreased BESS total scores during baseline testing, increased SCAT-3 symptom severity and BSI-18 GSI at the <48 h timepoint, and increased BSI-18 GSI at the asymptomatic timepoint. Elevated BSI-18 GSI was associated with increased SCAT-3 symptom severity and BESS total scores at all timepoints, increased SAC total scores during baseline testing, and decreased SAC scores at the <48 and asymptomatic timepoints. Participants who underwent baseline testing during CBT displayed significantly higher SCAT-3 symptom severity and BSI-18 GSI, and increased SAC and BESS total scores. Participants reporting at least one previous concussion displayed increased SAC total scores during baseline testing.

Discussion

The purpose of this study was to examine the relationship between sleep duration and clinical assessments (SCAT-3 symptom severity, BSI-18, SAC, BESS) used in concussion management at different evaluation timepoints in MSA cadets and midshipmen. Sleep was significantly associated with physical and psychological symptom endorsement, and cognitive and balance testing at different timepoints.

Impact of sleep on clinical assessments

In the current study, self-reported sleep impacted SCAT-3 symptom severity at each evaluation timepoint. Self-reported sleep duration has previously shown a strong correlation compared with actigraphy in subjective sleep onset time and a moderate correlation with self-reported sleep duration.³² Decreased sleep duration has been associated with elevated concussion symptom endorsement in uninjured adolescent athletes.²⁹ Collegiate athletes reporting less sleep at the <48 h timepoint relative to sleep recorded at baseline reported higher symptom severity scores (39.1 ± 20.7) compared with participants obtaining normal (25.1 ± 18.4) or increased sleep (25.7 ± 21.8).¹⁹ Increased concussion symptom severity has also been observed in adults reporting sleep problems during the subacute stages of concussion recovery (mean 37.0 ± 1.3 days postconcussion).³³ A bidirectional association between glymphatic system dysfunction and sleep impairment postconcussion may be a primary cause explaining the elevated symptom burdens.³⁴ Sleep disturbances are commonly reported postconcussion and in a healthy military population^15,16,19 leading to potential disruptions of the sleep-active glymphatic functionality of the brain.³⁴

Greater sleep duration was associated with decreased psychological distress at all timepoints. Sleep has been previously associated with psychological distress in a young healthy population with sleep quantity and duration displaying a moderate (r = 0.41) to small (r = −0.19) correlation with depressive symptom reporting.³⁵ The association between sleep and psychological distress has also been supported previously in adults postconcussion where participants with a concussion endorsed elevated acute psychological distress postinjury that improved over time but was impacted by poor sleep quality.³⁶ A relationship may exist between sleep quality and psychiatric distress³⁷ and a bidirectional relationship may also exist between poor sleep quality and psychological distress postconcussion.³⁶

After controlling for significant covariates, an association was observed between sleep and both balance and cognitive testing at baseline and specific postconcussion timepoints. A similar study assessing sleep duration and cognitive testing postconcussion reported no association between SAC total scores and sleep duration during recovery.¹⁹ This same study also found no association between sleep and balance testing postconcussion.¹⁹ There is evidence that participants with a self-reported sleep disorder display better balance, contradicting the results from the current study, and worse cognitive function than participants without a sleep disorder.³⁸ Sleep has been linked to deficits in memory, attention, visual perception, and visuomotor function.³³ The mechanisms contributing to these deficits include impaired memory consolidation and disrupted synaptic regulation that occur throughout the sleep cycle.³³ The association observed between sleep and balance may be explained by research suggesting obtaining adequate amounts the rapid eye movement sleep positively impacts motor control by regulating muscle tonus.³⁹

Impact of covariates on clinical assessments

In the current study, sex demonstrated a significant association with each clinical assessment at specific timepoints. Females have reported total symptom scores 1.45 and 0.88 points higher than males during baseline and postinjury assessments, respectively,⁴⁰ and males have displayed higher odds of reporting zero BSI-18 symptoms postconcussion.⁴¹ Females may be more honest regarding symptom reporting than males but symptom endorsement may also be driven by hormonal systems, neural architecture, and differences in the metabolic demands of the male and female brain.⁴² Previous research has reported no differences in SAC testing among an NCAA cohort based on sex⁴³ and concussed female collegiate athletes performed worse on the BESS than males.⁴⁴

Competition level had a significant association with clinical assessments at different timepoints with varsity cadets displaying decreased concussion symptom severity and psychological symptom burdens postinjury and elevated psychological symptom burdens during baseline testing. Varsity cadets displayed higher SAC scores at baseline and postinjury and elevated BESS total scores at baseline and lower BESS total scores postinjury. The decreased psychological and concussion symptom severity burdens and improved BESS total scores observed postinjury may be indicative of truncated recovery in varsity cadets²⁴ and may be explained by the different internal and external psychological pressures varsity athletes may experience.⁴⁵ Concussion history only displayed an association with SAC total scores during baseline testing. The lack of association between concussion history and clinical assessments has been supported previously in an NCAA population.⁴⁶

Participants who underwent baseline testing during CBT reported elevated SCAT-3 and BSI-18 symptom burdens, performed worse on the BESS, and scored higher on the SAC. A lack of sleep during basic military training has been associated with increased physical and psychological symptom burdens and additional indicators of inhibited performance.²³ The impact of CBT on baseline clinical measures may also reflect the novel psychological and physical toll new cadets must adjust to during their initial military training experience. In situations where baseline concussion testing must be conducted during CBT, the timing of testing administration should be considered. Results may be skewed when baseline testing is administered near taxing military training.

Limitations/future research

The population was comprised of young, physically active MSA members which may not be generalizable to the general population or people with comorbidities. Self-reported sleep was only based on the night preceding the evaluation and may not be indicative of sleep patterns over a longer period. The study methodology only allowed for the observation of associations between sleep and clinical measures at each time point, further research is needed to determine if this is a cause-and-effect relationship. Previous research has shown subjective, self-reported symptom scales like the SCAT-3 can be skewed to obtain a desired outcome.^47,48 Future research should assess sleep quality throughout concussion recovery using more precise methods,^49,50 to more accurately assess the impact of sleep on these assessments prospectively.

Conclusion

Sleep was associated with several different clinical assessment outcomes used in concussion management. Increased sleep was associated with decreased SCAT-3 symptom severity and BSI-18 GSI across different concussion management timepoints with a greater magnitude of association observed at the baseline and <48 h timepoints. Sleep may be associated with symptoms of physical and psychological distress reported throughout a standardized concussion management program. Sleep duration the night before baseline testing and postinjury evaluations should be considered when evaluating assessment outcomes. Based on these results, MSA members should be encouraged to get more sleep postconcussion.

Footnotes

Acknowledgments

This study was conducted at four United States Service Academies, the United States Military Academy, the United States Air Force Academy, the United States Naval Academy, and the United States Coast Guard Academy. The authors would like to thank Bonnie Campbell, Lisa Campbell, Megan Jackson, Jennifer Miley, and Kim Robb (United States Air Force Academy), Robin Miller and Jarrett Headley (United States Coast Guard Academy), Stephanie Carminati, Story Miraldi, Karen Peck, Jamie Reilly, Sean Roach, and Jesse Trump (United States Military Academy) for data acquisition, as well as the research and medical staff that assisted with baseline data collection at each of the three service academies. The authors would also like to thank Jaroslaw Harezlak, Jody Harland, Janetta Matesan, Larry Riggen (Indiana University), Ashley Rettmann (University of Michigan), Melissa Koschnitzke (Medical College of Wisconsin), Michael Jarrett, Vibeke Brinck, and Bianca Byrne (QuesGen), Thomas Dompier, Erin B. Wasserman, Milessa Niceley Baker, and Sara Quetant (Datalys Center for Sports Injury Research and Prevention).

Authors’ Contributions

M.J.A.: Conceptualization, data curation, formal analysis, investigation, methodology, validation, visualization, and writing—original draft. M.H.R.: Project administration, validation, and writing—review and editing. S.R.M.: Investigation and writing—review and editing. J.R.: Investigation and writing—review and editing. S.J.S.: Funding acquisition and methodology. J.B.R.: Writing–review and editing. G.T.M.: Methodology and investigation. J.C.J.: Writing—review and editing. D.E.C.: Investigation. C.A.E.: Investigation. R.B.: Investigation. K.V.P.: Validation and writing—review and editing. A.S.: Methodology and writing—review and editing. S.B.: Funding acquisition, methodology, and writing—review and editing. M.M.: Funding acquisition and methodology. T.W.M.: Funding acquisition and methodology. P.F.P.: Funding acquisition, methodology, and writing—review and editing. K.L.C.: Conceptualization, data curation, project administration, formal analysis, funding acquisition, methodology, validation, visualization, and writing—review and editing.

Author Disclosure Statement

There are no commercial relationships that may lead to a conflict of interest associated with this article. Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the Department of Defense.

Funding Information

This publication was made possible, in part, with support from the Grand Alliance Concussion Assessment, Research, and Education (CARE) Consortium, funded, in part by the National Collegiate Athletic Association (NCAA) and the Department of Defense (DOD). The US Army Medical Research Acquisition Activity, 820 Chandler Street, Fort Detrick MD 21702-5014 is the awarding and administering acquisition office. This work was supported by the Office of the Assistant Secretary of Defense for Health Affairs, through the Combat Casualty Care Research Program, endorsed by the Department of Defense, through the Joint Program Committee 6/Combat Casualty Care Research Program—Psychological Health and Traumatic Brain Injury Program under Award Nos. W81XWH1420151 and W81XWH1820047.

Abbreviations Used

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The Association Between Sleep Duration and Clinical Measures of Concussion at Baseline and Postinjury in the United States Service Academy Cadets and Midshipmen