The Alcohol and Drug Cognitive Enhancement (ACE) Screening Tool: A simple and brief questionnaire to screen for cognitive impairment in substance use disorder treatment services.

The objective of this study was to determine the test-retest reliability; construct and criterion validity; and test operating characteristics of a newly developed cognitive impairment risk factor screening instrument, the Alcohol and Drug Cognitive Enhancement (ACE) Screening Tool. Participants in the validation study were 129 adults with substance use disorder (SUD) enrolled in residential SUD treatment services and 209 normal controls. Test and retest data were available for 36 participants with SUD and 40 normal control individuals on the ACE Screening Tool. Test-retest reliability was excellent (ICC = 0.97). The ACE Screening Tool was significantly correlated with the Montreal Cognitive Assessment (MoCA), Behavior Rating Inventory of Executive Functioning-Adult Version (BRIEF-A), Test of Premorbid Functioning (TOPF) and Five Point Test, establishing construct validity. Criterion validity was established using a ternary severity variable constructed using results obtained on the MoCA and BRIEF-A. Test operating characteristics analysis showed 93% sensitivity, 46% specificity, 33% positive predictive power, and 96% negative predictive power using a cut-score of >3. Those high levels of sensitivity and negative predictive power indicated that the tool would likely detect cognitive impairment when present and should therefore be considered suitable as an initial screening tool for cognitive impairment in individuals attending SUD services.

A Psychometric Replication of Fan (1998) Item Response Theory and Classical Test Theory: An Empirical Comparison of their Item/Person Statistics.

Streiner, Norman and Cairney (2015) "Health Measurement Scales: A practical guide to their development and use", now in its fifth edition, is one of the foundational texts of the health outcomes movement. It states that "the differences between scales constructed with IRT and CTT are trivial." (Streiner, Norman and Cairney, 2015, p. 299) This statement is representative of the view which emphasizes the equivalence of True-Score Theory (TST) (also known as Classical Test Theory [CTT]) and the Rasch Measurement Model [RMM]). This view is widely held and has been one factor in limiting the application of RMM in the development of health outcome measures. However, this equivalence view relies heavily on a paper by Fan (1998) which examined the item statistics derived from TST, IRT (Item Response Theory) and the RMM for a large educational dataset. While subject to a number of theoretical and practical criticisms from a RMM perspective this paper has not been replicated with a large sample. This paper by replicating and extending the paper by Fan (1998) challenges the finding that item difficulty indexes derived from high and low ability samples using TST techniques are invariant. They are not. On the other hand, item locations derived from the RMM have a high degree of invariance. This secondary data analysis, by working through the methods used by Fan (1998) also demonstrates that a reliance on the magnitude of correlational coefficients cannot be used to determine the invariance of item difficulty indexes. An investigation into the linearity of the correlations using scatter plots is also required. Finally, an item analysis derived from the item difficulty indexes which displays a picture of the test as a whole shows that, for this large sample, the differences between scales constructed with TST and the RMM are not trivial.

Supplementation with Synbiotics and/or Branched Chain Amino Acids in Hepatic Encephalopathy: A Pilot Randomised Placebo-Controlled Clinical Study.

INTRODUCTION: Hepatic encephalopathy (HE) is common in patients with cirrhosis and is characterised by reduced hepatic ammonia clearance. This is accompanied by alterations in gut bacteria that may be ameliorated with synbiotics (pro- and prebiotics). Branched chain amino acids (BCAAs) are thought to have a role in the detoxification of ammonia. We investigated the effects of the administration of synbiotics and/or BCAAs in treating HE. METHODS: Participants with overt HE were randomised in a blinded placebo-controlled study to receive synbiotics, BCAAs, or a combination of BCAAs and Synbiotics. Relevant biochemical and nutritional data and depression and anxiety scores (DASS-21) were collected at entry, 4 weeks, and on completion, at 8 weeks. The Trail Making Test (TMT) and Inhibitory Control Test (ICT) were used to assess cognitive function in patients withHE. Results were analysed using linear mixed effects regression analyses. RESULTS: Sixty-one participants were enrolled and 49 who returned for at least 1 follow-up review were included in the intention to treat analysis. The mean age was 55.8 ± 6.1 years and 86% were males. Despite evidence of a placebo effect, there was significant improvement in TMT B and ICT weighted lures in participants who received combined synbiotics/BCAAs treatment compared to placebo at study completion (p ≤ 0.05). Cognitive improvement occurred without a significant change in ammonia levels. CONCLUSION: To our knowledge, this is the first study reporting that combined synbiotics and BCAAs improve HE, and that may be beneficial in the management of HE. A larger study is needed to confirm these results.

The Abbreviated Westmead Post-traumatic Amnesia Scale and Pocket Concussion Recognition Tool: Data from amateur sports players in live-match conditions.

Sports-related concussion is a growing public health concern. A short, simple sideline assessment tool is essential for evaluation of concussion at an amateur participation level. The current study examined responses to sideline assessment measures in a sample of amateur Australian Rules Football players competing in real-time live matches who had not sustained a concussion on the day of testing. Participants (N = 127) completed the Abbreviated Westmead Post-traumatic Amnesia Scale (A-WPTAS) and the Pocket Concussion Recognition Tool (Pocket CRT), which contains the Maddocks Questions (assessing orientation and recent memory) and the Postconcussion Symptom Scale (PCSS). The study showed 98.4% of participants passed the A-WPTAS, while 81.9% passed the Maddocks Questions. Participants endorsed a mean of 4.16 (SD = 4.02) symptoms on the PCSS, with 86.6% endorsing at least 1 symptom at a mild level or greater and 40.2% endorsing at least 1 symptom at a moderate or severe level. The current results suggest the Maddocks Questions may not be sufficient for use in an amateur sports context. To reduce the risk for a false positive diagnosis of concussion, it is recommended that the Pocket CRT be complemented with the A-WPTAS for use in an amateur sports context.

Déjà vecu for news events but not personal events: A dissociation between autobiographical and non-autobiographical episodic memory processing.

In déjà vu, the feeling that what we are currently experiencing we have experienced before is fleeting and is not accepted as true. In contrast, in déjà vecu or "recollective confabulation", the sense of déjà vu is persistent and convincing, and patients genuinely believe that they have lived through the current moment at some previous time. In previous reports of cases of déjà vecu, both personal events and non-personal, world events gave rise to this experience. In this paper we describe a patient whose déjà vecu experiences are entirely restricted to non-personal events, suggesting that autobiographical and non-autobiographical episodic memory processing can dissociate. We suggest that this dissociation is secondary to differences in the degree to which personal and emotional associations are formed for these two different types of event, and offer a two-factor theory of déjà vecu.

Identifying posttraumatic amnesia in individuals with a Glasgow Coma Scale of 15 after mild traumatic brain injury.

OBJECTIVE: To examine the utility of the Abbreviated Westmead Post-traumatic Amnesia Scale, which includes the Glasgow Coma Scale (GCS) and 3 picture cards used to measure amnesia, in identifying the presence or absence of posttraumatic amnesia in individuals with mild traumatic brain injury (mTBI). DESIGN: Prospective study using data from the Abbreviated Westmead Post-traumatic Amnesia Scale. SETTING: Trauma hospital. PARTICIPANTS: Individuals with possible mTBI who presented between April and September 2011 (N=252; age range, 18-65y; mean age, 37.4±13.9y; 77% men). INTERVENTION: Administration of the Abbreviated Westmead Post-traumatic Amnesia Scale. MAIN OUTCOME MEASURES: GCS and Abbreviated Westmead Post-traumatic Amnesia Scale pass/fail rates. RESULTS: Of the individuals, 169 (mean age, 35.1±13.6y; 77% men) received the scale. A pass/fail performance was achieved a median 121 minutes (interquartile range, 89-205min) after triage. Of the 45 who failed, 31 (69%) had a GCS score of 15. The likelihood of failing was associated with being older (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.02-1.06; P<.05), having consumed alcohol (OR, 3.09; 95% CI, 1.42-6.74; P<.01), and the scale being administered closer to the time of the injury (OR, 0.99; 95% CI, 0.99-1.00; P<.05). Nineteen (42%) of those who failed had consumed alcohol, 11 had a GCS score of 15, and 8 had a GCS score of 14. CONCLUSIONS: A GCS score of 15 does not always signify return to normative cognitive function. Individuals with a GCS score of 15 who are acutely cognitively impaired are at risk of not being accurately identified. The addition of an amnesia score to the GCS in the Abbreviated Westmead Post-traumatic Amnesia Scale will assist in making a diagnosis of mTBI.

A comparison of the degree of effort involved in the TOMM and the ACS Word Choice Test using a dual-task paradigm.

The aims of the current study were to: (a) examine the predictive validity and efficacy of the Advanced Clinical Solutions Word Choice Test (WCT) as a measure of effort relative to the Test of Memory Malingering (TOMM); (b) investigate whether performing a dual (distraction) task would undermine performance on either test; (c) assess the effect of coaching on the diagnostic accuracy of both the WCT and the TOMM; and (d) establish an optimal cut score for the WCT. The current study used a simulation design based on an analogue design in which normal participants were instructed to either apply full effort or simulate a brain injury on the tasks without being detected. Participants included 93 undergraduate university students who were randomly assigned to 1 of 4 conditions: (a) distraction, (b) uncoached traumatic brain injury (TBI) simulators, (c) coached TBI simulators, or (d) full effort. The results demonstrated that the WCT and the TOMM were effective in detecting simulated cognitive impairment. Both tests were resistant to the effects of distraction and were equally effective in detecting coached and uncoached simulators. A cut score of 42 on the WCT was found to provide optimal specificity and sensitivity on the test.

Paired associate learning in children with neurofibromatosis type 1: implications for clinical trials.

Studies investigating behavior in mice with a heterozygous null mutation of the NF1 gene (Nf1 (+/-)) have provided critical insights into the molecular and cellular mechanisms underlying cognitive impairments associated with neurofibromatosis type 1 (NF1). Hyperactivation of the Ras-MAPK signaling cascade, which results in increased GABA-mediated inhibition and significantly reduced long-term potentiation, has been proposed as a core mechanism underlying Nf1 (+/-) mice deficits in visuospatial learning and attention. This assertion has been reinforced by preclinical trials that reveal that these impairments can be rescued both at a cognitive and cellular level. We attempted to demonstrate a phenotypic parallel between Nf1 (+/-) mice and children with NF1 using a well-validated measure of visuospatial learning. Children with NF1 (n = 71) and healthy controls (n = 29) were assessed on a computerized paired associate learning task. Interrelationships between visuospatial learning and other cognitive abilities that may influence performance, such as intelligence, attention and visuospatial function, were explored. Children with NF1 displayed significant impairments in visuospatial learning, with reduced initial retention and poorer learning across repeated trials. Importantly, we demonstrated that visuospatial learning was inferior in NF1 even after accounting for group differences in intelligence, sustained attention and visuospatial abilities. We have thus identified impaired visuospatial learning as a core phenotypic feature in children with NF1. These findings imply that hippocampal-based learning networks are dysfunctional in children with NF1 and provide validation for a primary outcome measure for clinical trials aiming to correct aberrant Ras signaling.

Compliance with return-to-play regulations following concussion in Australian schoolboy and community rugby union players.

BACKGROUND: There is a risk of concussion when playing rugby union. Appropriate management of concussion includes compliance with the return-to-play regulations of the sports body for reducing the likelihood of premature return-to-play by injured players. PURPOSE: To describe the proportion of rugby union players who comply with the sports body's regulations on returning to play postconcussion. STUDY DESIGN: Prospective cohort study. METHODS: 1958 community rugby union players (aged 15-48 years) in Sydney (Australia) were recruited from schoolboy, grade and suburban competitions and followed over ≥1 playing seasons. Club doctors/physiotherapists/coaches or trained injury recorders who attended the game reported players who sustained a concussion. Concussed players were followed up over a 3-month period and the dates when they returned to play (including either a game or training session) were recorded, as well as any return-to-play advice they received. RESULTS: 187 players sustained ≥1 concussion throughout the follow-up. The median number of days before players returned to play (competition game play or training) following concussion was 3 (range 1-84). Most players (78%) did not receive return-to-play advice postconcussion, and of those who received correct advice, all failed to comply with the 3-week stand-down regulation. CONCLUSIONS: The paucity of return-to-play advice received by community rugby union players postconcussion and the high level of non-compliance with return-to-play regulations highlight the need for better dissemination and implementation of the return-to-play regulations and improved understanding of the underlying causes of why players do not adhere to return-to-play practices.

Diagnostic efficiency of ImPACT and CogSport in concussed rugby union players who have not undergone baseline neurocognitive testing.

The current study endeavored to replicate the approach to sports-related concussion management adopted by some community-based sporting organizations by examining the diagnostic efficiency of CogSport and ImPACT in athletes without baseline test data and assessed only once postinjury. Recently concussed nonelite-level rugby union players (N = 51) were tested within 72 hours of sustaining a concussion and were compared to nonconcussed matched controls (N = 41). Demographic information and history of recent concussion were also collected. Logistic regression analysis and receiver-operating characteristic curve analysis were conducted to evaluate the most accurate scores at identifying group membership. Overall, the classification accuracy of CogSport and ImPACT represented only very minimal improvements over a demographic-only (age, estimated premorbid Full-Scale IQ, and number of previous concussions) model. Positive predictive power and negative predictive power of composite scores were modest. The ImPACT postconcussion symptoms total (severity) score was most accurate at classifying concussed athletes. Where neuropsychological tests are utilized on a single occasion postconcussion and in the absence of baseline testing, postinjury testing does not improve diagnostic utility beyond the demographic model. These results do not validate this approach as a useful method of managing sports-related concussion.

Validation of the Abbreviated Westmead Post-traumatic Amnesia Scale: a brief measure to identify acute cognitive impairment in mild traumatic brain injury.

OBJECTIVE: To validate the use of the Abbreviated Westmead Post-traumatic Amnesia Scale (A-WPTAS) in the assessment of acute cognitive impairment in mild traumatic brain injury (mTBI). METHODS: Data previously collected from 82 mTBI and 88 control participants using the Revised Westmead Post-traumatic Amnesia Scale (R-WPTAS) was converted to A-WPTAS scores and pass/fail classifications were calculated for both scales. RESULTS: The proportion of failures on the R-WPTAS and the A-WPTAS did not differ and a similar number of mTBIs were classified on each. For mTBIs the relationship between the independent memory test and a pass/fail classification was the same for both scales. Bivariate logistic regressions revealed that mTBIs, relative to controls, were around 8 times more likely to fail the assessment (R-WPTAS: 95% CI: 3.70-18.87; A-WPTAS: 95% CI: 3.70-20.14). As verbal learning improved the likelihood of failure was reduced. Greater education was associated with a decreased likelihood of failure. The relationship between education and a fail performance was not sustained when education was adjusted for the effect of age, prior mTBI, blood alcohol level, injury status, verbal learning, and morphine administration. CONCLUSIONS: The A-WPTAS is a valid measure. The A-WPTAS may reduce the risk of failing to classify patients with mTBI by identifying and documenting acute cognitive impairment.

The prospective course of postconcussion syndrome: the role of mild traumatic brain injury.

OBJECTIVE: To investigate whether postconcussion syndrome (PCS) represents long-term sequelae associated with mild traumatic brain injury (mTBI). METHODS: Prospective consecutive admissions to a Level 1 trauma hospital were assessed a mean 4.9 days and again 106.2 days post-injury. The final sample comprised 62 mTBI and 58 nonbrain injured trauma controls (TC). Change or lack of change in individual PCS-like symptoms and PCS was examined. Multilevel logistic regression was used to analyze whether mTBI predicts 3-month PCS (Time 2; T2); whether predictors of PCS (within 14 days of injury, Time 1; T1) predict 3-month PCS, and how change in these predictors from T1 to T2 were associated with change in PCS status. Variables included demographic, injury-related, financial incentives, neuropsychological, and psychiatric disorder. RESULTS: MTBI did not predict PCS. PCS was comparable (T1: mTBI: 40.3%, TC: 50.0%; T2: mTBI: 46.8%, TC: 48.3%). At T2, 38.6% were new cases of PCS; between 30.8% and 86.2% reported either a new or more frequent symptom. A pre-injury depressive or anxiety disorder (OR = 2.99, 95% CI [1.38, 6.45]), and acute posttraumatic stress (OR = 1.05, 95% CI [1.00, 1.00]) were early markers of PCS, regardless of mTBI. An interaction between time and posttraumatic stress disorder (PTSD) suggested the relationship between the severity of PTSD symptoms and PCS strengthened over time (OR = 2.66, 95% CI [1.08, 6.55]). Pain was related to PCS. Females were more likely than males to have PCS. CONCLUSION: The data suggest the phenomenon of PCS in trauma patients does not show an association with mTBI.

Mild traumatic brain injury among a cohort of rugby union players: predictors of time to injury.

This study reports the time to sustain a mild traumatic brain injury (mTBI) among a cohort of community rugby union players. Demographic and player characteristics were collected and players followed up for between one and three playing seasons. 7% of the cohort sustained an mTBI within 10 h of game time, increasing twofold to 14% within 20 h. The mean time to first mTBI was 8 h with an SD of 6.2 (median 6.8 h; IQR: 2.9-11.7 h). Players reporting a recent history of concussion were 20% more likely to sustain an mTBI after 20 h of game time compared with those with no recent history of concussion. Players were likely to sustain an mTBI in shorter time if they trained for <3 h/week (HR=1.48, p=0.03) or had a body mass index <27 (HR=1.77, p=0.007). The findings highlight modifiable characteristics to reduce the likelihood of shortened time to mTBI.

Assessment of executive function and attention in children with neurofibromatosis type 1: relationships between cognitive measures and real-world behavior.

The aim of this study was to examine functional attention and executive deficits present in everyday living in a large sample of children with neurofibromatosis type 1 (NF1). Data are presented from 199 children with NF1 and 55 unaffected sibling controls who were administered the Behavior Rating Inventory of Executive Function (BRIEF) and Conners' ADHD DSM-IV Scales (CADS). Convergent validity was examined by correlating scale scores from these functional measures with scores from traditional cognitive measures of attention and executive function. Results indicated global functional attention and executive deficits in children with NF1. Relationships between functional impairments and scores on cognitive measures were inconsistent; at best, the magnitude of these relationships was in the moderate range, yet there was also a lack of association between many cognitive tasks and the functional skills they purport to assess. Findings suggest that cognitive and functional measures may tap different constructs and that neuropsychological evaluations should be supplemented with functional assessment tools to provide a more accurate and sensitive encapsulation of a child's strengths and weaknesses to guide remediation programs.

The cognitive profile of preschool-aged children with neurofibromatosis type 1.

Few studies have examined the cognitive profile of young children with NF1. In this study, 26 children with NF1 (M(age) = 5 years 3 months) were compared with 21 peer comparisons (M(age) = 4 years 8 months) and available normative data on neuropsychological measures. Children with NF1 demonstrated the characteristic downward shift in IQ, poor visuospatial constructional skills, and inattention. Working memory deficits were common in parental ratings. These findings suggest that at least some of the cognitive deficits associated with NF1 can be identified in the preschool-age group, highlighting the need for early assessment and intervention.

Visuomotor integration deficits precede clinical onset in Huntington's disease.

OBJECTIVES: Visuomotor integration deficits have been documented in Huntington disease (HD), with disproportionately more impairment when direct visual feedback is unavailable. Visuomotor integration under direct and indirect visual feedback conditions has not been investigated in the stage before clinical onset ('premanifest'). However, given evidence of posterior cortical atrophy in premanifest HD, we predicted visuomotor integration would be adversely affected, with greater impairment under conditions of indirect visual feedback. METHODS: 239 subjects with the HD CAG expansion, ranging from more than a decade before predicted clinical onset until early stage disease, and 122 controls, completed a circle-tracing task, which included both direct and indirect visual feedback conditions. Measures included accuracy, speed, and speed of error detection and correction. Using brain images acquired with 3T magnetic resonance imaging (MRI), we generated grey and white matter volumes with voxel-based morphometry, and analyzed correlations with circle-tracing performance. RESULTS: Compared with controls, early HD was associated with lower accuracy and slower performance in both circle-tracing conditions. Premanifest HD was associated with lower accuracy in both conditions and fewer rotations in the direct condition. Comparing performance in the indirect condition with the direct condition, HD gene expansion-carriers exhibited a disproportionate increase in errors relative to controls. Premanifest and early HD groups required longer to detect and correct errors, especially in the indirect condition. Slower performance in the indirect condition was associated with lower grey matter volumes in the left somatosensory cortex in VBM analyses. CONCLUSIONS: Visuomotor integration deficits are evident many years before the clinical onset of HD, with deficits in speed, accuracy, and speed of error detection and correction. The visuomotor transformation demands of the indirect condition result in a disproportionate decrease in accuracy in the HD groups. Slower performance under indirect visual feedback was associated with atrophy of the left-hemisphere somatosensory cortex, which may reflect the proprioceptive demands of the task.

Reduced processing speed in rugby union players reporting three or more previous concussions.

The issue pertaining to the effect of multiple self-reported sports-related concussions on cognitive function is controversial. Although this topic has received increased attention in the literature recently, the issue remains unresolved. Evidence supporting a detrimental cognitive effect has been reported at a sub-concussive level and following one, two, and three or more previous concussions. However, numerous studies have been unable to replicate these findings. Additionally, discrepancies between neuropsychological testing formats have been identified, where studies utilizing traditional tests tend to support the notion of detrimental cognitive effects whereas studies with computerized tests have tended to demonstrate no effect. The present study sought to examine possible detrimental cognitive effects in a sample of adult male rugby union players who reported a history of three or more concussions (n = 34) compared with those who reported no previous concussions (n = 39). A computerized neuropsychological battery and a traditional neuropsychological measure of processing speed were administered for this purpose. Findings revealed that there were differences between groups on two processing speed measures from both traditional and computerized tests. Athletes with a history of multiple concussions performed significantly lower on these measures than those with no history of concussion. These results provide further evidence to suggest that a history of three or more self-reported concussions in active athletes may have a detrimental effect on cognitive function. Future research may focus on identifying moderating factors in an attempt to resolve some of the conflicting findings and identify potential athletes at risk for sustaining cognitive deficits.

Corpus callosum morphology and its relationship to cognitive function in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is associated with cognitive dysfunction and structural brain abnormalities such as an enlarged corpus callosum. This study aimed to determine the relationship between corpus callosum morphology and cognitive function in children with neurofibromatosis type 1 using quantitative neuroanatomic imaging techniques. Children with neurofibromatosis type 1 (n = 46) demonstrated a significantly larger total corpus callosum and corpus callosum index compared with control participants (n = 30). A larger corpus callosum index in children with neurofibromatosis type 1 was associated with significantly lower IQ, reduced abstract concept formation, reduced verbal memory, and diminished academic ability, specifically reading and math. Our results suggest an enlarged corpus callosum in children with neurofibromatosis type 1 is associated with cognitive impairment and may provide an early structural marker for the children at risk of cognitive difficulties. Cognitive deficits associated with structural brain abnormalities in neurofibromatosis type 1 are unlikely to be reversible and so may not respond to proposed pharmacological therapies for neurofibromatosis type 1-related cognitive impairments.

A randomized controlled trial of cognitive remediation in schizophrenia.

Individuals with schizophrenia have consistently been found to exhibit cognitive deficits, which have been identified as critical mediators of psychosocial functional outcomes. Recent reviews of cognitive remediation (CRT) have concluded that these deficits respond to training. This multi-site community study examined 40 individuals with schizophrenia who underwent cognitive remediation using the Neuropsychological Educational Approach to Remediation(1) (NEAR). Assessments using the same neuropsychological tests and measures of psychosocial outcome were made at four time points: baseline, before start of active intervention, end of active intervention and 4 months after end of active intervention. Dose of antipsychotic medication remained constant throughout the study period. After participating in NEAR, individuals showed significant improvements in verbal and visual memory, sustained attention and executive functioning. This effect persisted 4 months after the treatment ceased. The average effect size was mild to moderate. Social and occupational outcomes also improved from baseline to post-treatment, which persisted 4 months later. Our findings replicate those of previous studies that suggest that NEAR is effective in improving cognition in individuals with schizophrenia in a naturalistic and ecologically valid setting. Further it extends such findings to show a generalisation of effects to social/occupational outcomes and persistence of effects in the short term.

Incidence, risk, and protective factors of mild traumatic brain injury in a cohort of Australian nonprofessional male rugby players.

BACKGROUND: Mild traumatic brain injury (mTBI) is an emerging public health issue in high-contact sports. Understanding the incidence along with the risk and protective factors of mTBI in high-contact sports such as rugby is paramount if appropriate preventive strategies are to be developed. PURPOSE: To estimate the incidence and identify the risk and protective factors of mTBI in Australian nonprofessional rugby players. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A cohort of 3207 male nonprofessional rugby players from Sydney, Australia, was recruited and followed over 1 or more playing seasons. Demographic information, history of recent concussion, and information on risk and protective factors were collected. The incidence of mTBI was estimated and the putative risk and protective factors were modeled in relation to mTBI. RESULTS: The incidence of mTBI was 7.97 per 1000 player game hours, with 313 players (9.8%) sustaining 1 or more mTBIs during the study. Players who reported always wearing protective headgear during games were at a reduced risk (incident rate ratio [IRR], 0.57; 95% confidence interval [CI], 0.40-0.82) of sustaining an mTBI. In contrast, the likelihood of mTBI was almost 2 times higher among players who reported having sustained either 1 (IRR, 1.75; 95% CI, 1.11-2.76) or more mTBIs (IRR, 1.65; 95% CI, 1.11-2.45) within the 12 months before recruitment. CONCLUSION: Nonprofessional rugby has a high incidence of mTBI, with the absence of headgear and a recent history of mTBI associated with an increased risk of subsequent mTBI. These findings highlight that both use of headgear and the management of prior concussion would likely be beneficial in reducing the likelihood of mTBI among nonprofessional rugby players, who compose more than 99% of rugby union players in Australia.