Evaluating the "threshold Theory": Can Head Impact Indicators Help?

Purpose This study aimed to determine the clinical utility of biomechanical head impact indicators by measuring the sensitivity, specificity, positive predictive value (PV+), and negative predictive value (PV-) of multiple thresholds. Methods Head impact biomechanics (n = 283,348) from 185 football players in one Division I program were collected. A multidisciplinary clinical team independently made concussion diagnoses (n = 24). We dichotomized each impact using diagnosis (yes = 24, no = 283,324) and across a range of plausible impact indicator thresholds (10g increments beginning with a resultant linear head acceleration of 50g and ending with 120g). Results Some thresholds had adequate sensitivity, specificity, and PV-. All thresholds had low PV+, with the best recorded PV+ less than 0.4% when accounting for all head impacts sustained by our sample. Even when conservatively adjusting the frequency of diagnosed concussions by a factor of 5 to account for unreported/undiagnosed injuries, the PV+ of head impact indicators at any threshold was no greater than 1.94%. Conclusions Although specificity and PV- appear high, the low PV+ would generate many unnecessary evaluations if these indicators were the sole diagnostic criteria. The clinical diagnostic value of head impact indicators is considerably questioned by these data. Notwithstanding, valid sensor technologies continue to offer objective data that have been used to improve player safety and reduce injury risk

Laboratory Validation of Two Wearable Sensor Systems for Measuring Head Impact Severity in Football Players

Wearable sensors can measure head impact frequency and magnitude in football players. Our goal was to quantify the impact detection rate and validity of the direction and peak kinematics of two wearable sensors: a helmet system (HITS) and a mouthguard system (X2). Using a linear impactor, modified Hybrid-III headform and one helmet model, we conducted 16 impacts for each system at 12 helmet sites and 5 speeds (3.6–11.2 m/s) (N = 896 tests). Peak linear and angular accelerations (PLA, PAA), head injury criteria (HIC) and impact directions from each device were compared to reference sensors in the headform. Both sensors detected ~96% of impacts. Median angular errors for impact directions were 34° for HITS and 16° for X2. PLA, PAA and HIC were simultaneously valid at 2 sites for HITS (side, oblique) and one site for X2 (side). At least one kinematic parameter was valid at 2 and 7 other sites for HITS and X2 respectively. Median relative errors for PLA were 7% for HITS and -7% for X2. Although sensor validity may differ for other helmets and headforms, our analyses show that data generated by these two sensors need careful interpretation

Osteoarthritis prevalence in retired national football league players with a history of ankle injuries and surgery

Context: Ankle injuries are common at all levels of American football, and retired National Football League (NFL) players have a high prevalence of osteoarthritis (OA), but little is known about how ankle injuries influence OA prevalence and daily activities in this population or how surgical interventions for such injuries alter the risk of OA. Objective: To examine (1) the association of ankle-injury history with OA prevalence, (2) the association of surgical intervention after ankle injury with OA prevalence, and (3) the relationships among ankle injuries, reported OA, and daily activities in retired NFL players. Design: Case-control study. Setting: Survey. Patients or Other Participants: Data from the Retired NFL Players General Health Survey. Main Outcome Measure(s): We created a 7-category main exposure variable that differentiated respondents by football-related ankle injury and surgical intervention. Multivariable binomial regression models were used to estimate prevalence ratios and 95% confidence intervals. Among those reporting OA, we examined the distribution of responses regarding whether OA affected daily activities. Results: Among the 2446 respondents, 920 participants experienced OA in any joint during their lifetime. Compared with those reporting no ankle injuries, the prevalence of OA was higher among those with a history of ankle injury. Also, the prevalence of OA was higher among those who had undergone surgery versus those who had not. The number of retired NFL players who reported that OA often affected their daily activities increased with the number of ankle injuries. Conclusions: Among former NFL players, a history of ankle injury increased the prevalence of OA. More ankle injuries increased the probability that OA negatively affected daily activities. Future prospective research is needed to better determine the influence of surgical intervention at the ankle or foot on OA

Functional balance assessment in recreational college-aged individuals with a concussion history

Objectives: Despite evidence for increased musculoskeletal injury after concussion recovery, there is a lack of dynamic balance assessments that could inform management and research into this increased injury risk post-concussion. Our purpose was to identify tandem gait dynamic balance deficits in recreational athletes with a concussion history within the past 18-months compared to matched controls. Design: Cross-sectional, laboratory study. Methods: Fifteen participants with a concussion history (age: 19.7 ± 0.9 years; 9 females; median time since concussion 126 days, range 28–432 days), and 15 matched controls (19.7 ± 1.6 years; 9 females) with no recent concussion history participated. We measured center-of-pressure (COP) outcomes (velocity, path length, speed, dual-task cost) under 4 tandem gait conditions: (1) tandem gait, (2) tandem gait, eyes closed, (3) tandem gait, eyes open, cognitive distraction, and (4) tandem gait, eyes closed, cognitive distraction. Results: The concussion history group demonstrated slower tandem gait velocity compared to the control group (4.0 cm/s difference), thus velocity was used as a covariate when analyzing COP path length and speed. The concussion history group (23.5%) demonstrated greater COP speed dual-task cost than the control group (16.3%) during the eyes closed dual-task condition. No other comparisons were statistically significant. Conclusions: There may be subtle dynamic balance differences during tandem gait that are detectable after return-to-activity following concussion, but the clinical significance of these findings is unclear. Longitudinal investigations should identify acute movement deficits in varying visual and cognitive scenarios after concussion in comparison with recovery on traditional concussion assessment tools while also recording musculoskeletal injury outcomes

Relationship between concussion history and concussion knowledge, attitudes, and disclosure behavior in high school athletes

Objective: Examine the association between self-reported concussion history and measures of concussion knowledge, attitude, and disclosure behavior. Design: Cross-sectional survey. Setting: Classroom. Participants: A convenience sample of high school athletes (n = 167; mean age = 15.7 years) from multiple sports completed a validated survey. Independent Variables: Concussion history (main predictor) was defined as the number of self-recalled concussions during participants' high school career. Main Outcome Measures: The outcomes were recalled concussion disclosure behavior (3 measures) and scales assessing both concussion knowledge and concussion attitude. Results: A greater number of previous concussions was associated with worse attitude to concussion and negative concussion disclosure behavior. For every 3 additional self-recalled concussions, there was a mean decrease of 7.2 points (range of possible scores = 14-98) in concussion attitude score (P = 0.002), a 48% decrease in the self-reported proportion of concussion events disclosed (P = 0.013), and an increased prevalence of self-reported participation in games (67%) and practices (125%) while experiencing signs and symptoms of concussion (P < 0.001). Increased concussion history did not affect concussion knowledge score (P = 0.333). Conclusions: Negative trends in concussion disclosure behavior were identified in youth athletes with a positive history of concussion. Improving disclosure in this subgroup will require targeted efforts addressing negative attitude to concussion

Reaction Time and Joint Kinematics During Functional Movement in Recently Concussed Individuals

Objective: To compare movement reaction time and joint kinematics between athletes with recent concussion and matched control recreational athletes during 3 functional tasks. Design: Cross-sectional. Setting: Laboratory. Participants: College-aged recreational athletes (N=30) comprising 2 groups (15 participants each): (1) recent concussion group (median time since concussion, 126d; range, 28–432d) and (2) age- and sex-matched control group with no recent concussions. Interventions: We investigated movement reaction time and joint kinematics during 3 tasks: (1) jump landing, (2) anticipated cut, and (3) unanticipated cut. Main Outcome Measures: Reaction time and reaction time cost (jump landing reaction time–cut reaction time/jump landing reaction time×100%), along with trunk, hip, and knee joint angles in the sagittal and frontal planes at initial ground contact. Results: There were no reaction time between-group differences, but the control group displayed improved reaction time cost (10.7%) during anticipated cutting compared with the concussed group (0.8%; P=.030). The control group displayed less trunk flexion than the concussed group during the nondominant anticipated cut (5.1° difference; P=.022). There were no other kinematic between-group differences (P≥.079). Conclusions: We observed subtle reaction time and kinematic differences between individuals with recent concussion and those without concussion more than a month after return to activity after concussion. The clinical interpretation of these findings remains unclear, but may have future implications for postconcussion management and rehabilitation

Association between concussion and mental health in former collegiate athletes

Background: The existing research on the association between concussion and mental health outcomes is largely limited to former professional athletes. This cross-sectional study estimated the association between recurrent concussion and depression, impulsivity, and aggression in former collegiate athletes. Methods: Former collegiate athletes who played between 1987–2012 at a Division I university completed an online questionnaire. The main exposure, total number of self-recalled concussions (sport-related and non-sport-related), were categorized as: zero (referent), one, two, or three or more concussions. The main outcomes were the depression module of The Patient Health Questionnaire (PHQ-9), the Short Form of the Barratt Impulsiveness scale (BIS15); and the 12-item Short Form of the Buss-Perry Aggression Questionnaire (BPAQ-SF). Depression was categorized into a binomial severity classification that differentiated between no or mild depression (PHQ-9 scores <10) and moderate to severe depression (PHQ-9 scores ≥10). Impulsivity and aggression were kept as continuous outcomes. Binomial regression estimated adjusted prevalence ratios (PR). Linear regression estimated adjusted mean differences (MD). Results: Of the 797 respondents with complete data (21.9% completion rate), 38.8% reported at least one concussion. Controlling for alcohol dependence and family history of depression, the prevalence of moderate to severe depression among former collegiate athletes reporting three or more concussions in total was 2.4 times that of those reporting zero concussions [95% Confidence Interval (CI): 1.0, 5.7]. Controlling for alcohol dependence, family history of anxiety, relationship status, obtaining a post-graduate degree, and playing primary college sport professionally, former collegiate athletes reporting two or more concussions in total had higher mean scores for impulsivity, compared to those reporting no concussions (2 concussions MD = 2.7; 95% CI: 1.2, 4.1; 3+ concussions MD = 1.9; 95% CI: 0.6, 3.2). Controlling for alcohol dependence, sex, and relationship status, former collegiate athletes reporting three or more concussions in total had a higher mean score for aggression, compared to those reporting no concussions (MD = 3.0; 95% CI: 1.4, 4.7). Conclusions: Our study found an association between former concussion and greater risk of severe depression and higher levels of impulsivity and aggression among former collegiate athletes. Additional prospective studies better addressing causality and ascertaining valid lifetime concussion histories and medical histories are needed

Agreement between athlete-recalled and clinically documented concussion histories in former collegiate athletes

Background: Athlete-recalled and clinically documented concussion histories have been used in research on former athletes, but both have limitations. Comparisons of these 2 types of concussion histories are needed to improve the accuracy of estimates of concussion history for future research and clinical care. Purpose: To estimate the agreement between athlete-recalled and clinically documented concussion histories during college and to explore reasons for differences. Study: Cohort study (diagnosis); Level of evidence, 3. Methods: Athlete-recalled concussion histories were provided by a convenience sample of 130 former collegiate athletes using an online questionnaire, and they were individually linked to previously collected clinical data that tracked medically diagnosed concussions at the host institution from 1996 to 2012. The intraclass correlation coefficient (ICC2,1) was used to assess agreement between athlete-recalled and clinically documented concussion histories. Descriptive analyses were performed to assess reasons for disagreement. Results: Agreement between athlete-recalled and clinically documented concussion histories was low (ICC2,1 = 0.21; 95% confidence interval, 0.05-0.37), but it was higher for women (ICC2,1 = 0.65; 95% confidence interval, 0.44-0.79) and for athletes playing more recently (2005-2012; ICC2,1 = 0.39; 95% confidence interval, 0.01-0.67). Of the 53 athletes who self-reported college sportsrelated concussions, 40% believed that they sustained impacts that should have been diagnosed as concussions but were undetected, and 21% admitted nondisclosure of suspected concussions. Common reasons for nondisclosure included the following: did not think injury was serious enough (91%), did not know it was a concussion (73%), and did not want to leave the game/practice (73%). Conclusion: Given the low agreement between athlete-recalled and clinically documented concussion histories, methodologic research is needed to improve the quality of tools used to assess concussion histories in former athletes. © 2014 The Author(s)

Concussion Nondisclosure During Professional Career Among a Cohort of Former National Football League Athletes

Background: Despite a focus on the incidence and effects of concussion, nondisclosure of sports-related concussions among retired players from the National Football League (NFL) has yet to be examined. Purpose: Examine the prevalence of and factors associated with nondisclosure of sports-related concussions in former NFL athletes. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A sample of 829 former NFL players completed a general health survey. This historical cohort included players who had played before World War II to 2001. Respondents retrospectively recalled sports-related concussions that they sustained during their professional careers and whether at least one of these sports-related concussions was not reported to medical staff. We computed the prevalence of nondisclosure among those recalling sport-related concussions during their professional careers. Multivariable binomial regression estimated adjusted prevalence ratios (PR) with 95% confidence intervals (CIs) controlling for race/ethnicity, number of years played, primary position played, professional career concussion history, and playing era. Playing era was categorized by whether the majority of a player’s career was before or after a 1976 rule change to limit contact (“spearing”). Results: Overall, 417 (50.3%) respondents reported they had sustained a concussion and did not inform medical staff at least once during their professional playing career. Nonwhite respondents had a higher prevalence of nondisclosure than white/non-Hispanic respondents (adjusted PR = 1.19; 95% CI, 1.02-1.38). An interaction between professional career concussion history and playing era was also found (P =.08). Compared with those in the pre–spearing rule change group with 1 or 2 concussions, all other groups had larger prevalences of nondisclosure (increases ranging from 41% to 153% in multivariable models). Across concussion strata, nondisclosure prevalence was generally higher in the post–spearing rule change group than the pre–spearing rule change group, with the largest differences found among those with 1 or 2 concussions or those with 3 or 4 concussions. Conclusion: A large proportion of former NFL players in this historical cohort reported at least one instance of not disclosing sports-related concussions to medical staff. Future research on concussion nondisclosure needs to identify mechanisms to improve football players’ intentions to disclose concussion-related symptoms to health care providers and to equip health care providers with more effective strategies for timely identification of concussion

Associations between BMI Change and Cardiometabolic Risk in Retired Football Players

Purpose Elevated rates of cardiometabolic diseases have been observed in former American football players. The current study sought to determine whether change in body mass index (ΔBMI) after retirement influences the prevalence of CHD, diabetes, or high blood pressure (HBP) in former professional football players. Methods Retired professional football players (n = 3729) were sent a survey with questions regarding health status, playing history, and demographic information. Self-reported BMI at the time of retirement was subtracted from current self-reported BMI to calculate ΔBMI. Prevalence of CHD, diabetes, and HBP were determined by asking participants if they had ever been diagnosed by a health care professional. Binomial regression with a Poisson residual and robust variance estimation was used to compute crude prevalence ratios (PR) and 95% confidence intervals (CI) for each outcome. Adjusted PR values were calculated by adjusting for BMI at the time of retirement, age, years of football experience, race, exercise habits, alcohol use, steroid history, smoking history, and playing position. Results Complete data were available for 2062 respondents. Prevalence of CHD increased 25%-31% for each five-point increase in ΔBMI after retirement (crude PR = 1.25, 95% CI = 1.03-1.52, P = 0.026; adjusted PR = 1.31, 95% CI = 1.11-1.55, P = 0.001). Diabetes prevalence increased 69%-88% for each five-point ΔBMI increase (crude = 1.88, 95% CI = 1.45-2.44, P < 0.001; adjusted = 1.69, 95% CI = 1.32-2.15, P < 0.001). A five-point increase in ΔBMI was associated with a 35%-40% increase in HBP prevalence (crude = 1.40, 95% CI = 1.27-1.53, P < 0.001; adjusted = 1.35, 95% CI = 1.24-1.47, P < 0.001). Conclusions After controlling for relevant covariates, postretirement ΔBMI was positively and independently associated with prevalence of CHD, diabetes, and HBP. Postretirement interventions using diet and/or exercise to influence body composition may improve long-term health in retired football players