Repetitive Impact Research Articles

Accumulative Damages of Thermally Sprayed Cemented Carbide Coatings Under Repetitive Heavy-Load Impacts

Accumulative Damages of Thermally Sprayed Cemented Carbide Coatings Under Repetitive Heavy-Load Impacts

Effectiveness of High Load Plantar Fascia Resistance Training among Athletes with Plantar Fasciitis

Background: Plantar fasciitis is a common condition characterized by pain and inflammation in the plantar fascia,a thick band of tissue that runs along the bottom of the feet, connecting the heel to the toes. It is particularlyprevalent among athletes who engage in activities that involve repetitive impact, such as running, jumping.Athletes with plantar fasciitis often undergo a structured rehabilitation program that incorporates high loadresistance training alongside other interventions such as stretching, massage, orthotic devices, and modificationsin training and footwear.Purpose: To compare the effectiveness of High Load Plantar Fascia Resistance Training with ultrasound andIntrinsic Muscle strengthening with ultrasound among athletes with Plantar Fasciitis.Materials and Methods: Total of 60 subjects were selected from Sri Sai Ortho General Clinic based on the selectioncriteria and randomly divided into two groups; High load plantar fascia resistance training (HLST) with ultrasound(n=30) and Intrinsic muscle strengthening with ultrasound (n=30). The subjects were assessed for pain intensityusing NPRS and using LEFS, for pre and post-test values. The interventions were given for 2 weeks. Study period: November 2022 to March 2023Result: The result of the study revealed that both exercises are effective but (HLST) with ultrasound was moreeffective and significant in terms of decreasing pain and improving functional mobility.Conclusion: Hence the study concludes that HLST was more effective in managing plantar fasciitis in terms ofboth relieving pain as well as functional mobility among athletes with plantar fasciitis.

An ongoing secondary task can reduce the illusory truth effect.

People are more likely to believe repeated information-this is known as the Illusory Truth Effect (ITE). Recent research on the ITE has shown that semantic processing of statements plays a key role. In our day to day experience, we are often multi-tasking which can impact our ongoing processing of information around us. In three experiments, we investigate how asking participants to engage in an ongoing secondary task in the ITE paradigm influences the magnitude of the effect of repetition on belief. Using an adapted ITE paradigm, we embedded a secondary task into each trial of the encoding and/or test phase (e.g., having participants count the number of vowels in a target word of each trivia claim) and calculated the overall accuracy on the task. We found that the overall ITE was larger when participants had no ongoing secondary task during the experiment. Further, we predicted and found that higher accuracy on the secondary task was associated with a larger ITE. These findings provide initial evidence that engaging in an ongoing secondary task may reduce the impact of repetition. Our findings suggest that exploring the impact of secondary tasks on the ITE is a fruitful area for further research.

Effects of Low-Load, High-Repetition Resistance Training on Maximum Muscle Strength and Muscle Damage in Elite Weightlifters: A Preliminary Study

This study aimed to assess the impact of different resistance training (RT) loads and repetition on muscle damage, intramuscular anabolic signaling, and maximal muscle strength (MMS) in weightlifters. Eighteen male weightlifters were randomly assigned to 8 weeks of supervised RT regimes: high-load, low-repetition (HL), low-load, high-repetition (LH), and combination of HL and LH (COMBI). All groups exhibited a significant increase in skeletal muscle mass (SMM) and growth hormone levels, which ultimately contributed to improvement in MMS as indicated by 1-repetition maximum in the back squat and back muscle strength. Notably, while there were no significant changes in the mTOR protein, the phosphorylation of phosphorylation of p70 ribosomal protein S6 kinase 1 (p70S6K1), eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), and eukaryotic elongation factor 2 (eEF2), which are involved in muscle cell growth, was significantly affected by the different training regimens. More importantly, LH-RT led to a significant reduction in muscle damage markers, creatine kinase (CK) and lactate dehydrogenase (LDH), suggesting reduced recovery time and fatigue. Our results demonstrated that the LH-RT paradigm could be a viable alternative for weightlifters to enhance MMS and muscle hypertrophy similar to HL-RT, while reducing RT-induced muscle damage, ultimately contributing to the enhancement of exercise performance.

Characterizing Cerebrovascular Pathologies in Brain Donors Exposed to Repetitive Head Impacts

AbstractBackgroundRepetitive head impacts (RHI) from American style football (ASF) and other contact sports are a known risk factor for the neurodegenerative disease chronic traumatic encephalopathy (CTE). RHI can also lead to mixed neuropathologies that uniquely contribute to clinical symptoms. Here, we compared various types of vascular and white matter pathologies between brain donors with and without exposure to RHI from different types of contact and collision sports (CCS).MethodsThe sample included 79 deceased male ASF players (RHI‐ASF) and 49 deceased male non‐ASF CCS athletes (RHI‐CCS) from the UNITE brain bank. Each RHI group had a comparison group that included similar aged (+/‐ 5 years) male brain donors without RHI from the Boston University Alzheimer’s Disease Research Center and Framingham Heart Study brain banks. The modified Ischemic Injury Scale (mIIS) served as a global indicator of vascular and white matter pathologies and is a sum of hippocampal sclerosis, infarct/lacune, microinfarct, microbleeds, laminar necrosis, arteriolosclerosis, atherosclerosis of Circle of Willis, cerebral amyloid angiopathy, and white matter rarefaction. Dementia diagnoses were made during consensus conferences. Linear or logistic regression compared the RHI vs non‐RHI groups on the mIIS and its subcomponents. Logistic regression models examined the association between mIIS and dementia. Models were adjusted for age.Results Table 1 shows sample characteristics. The RHI‐CCS group was comprised of boxers, amateur wrestlers, and ice hockey, soccer, rugby, and lacrosse players. 94 decedents had CTE, all of whom were in an RHI exposed group. Of the mIIS components, arteriolosclerosis was the most common across all groups. White matter rarefaction was also the most frequent mIIS component for both RHI groups, but not for non‐RHI groups. Compared to their respective controls, RHI‐ASF and RHI‐CCS were associated with higher mIIS scores (Table 2). Higher mIIS scores corresponded to increased odds for having dementia in both the RHI‐ASF and RHI‐CCS groups (Table 2). White matter rarefaction best discriminated both RHI groups from non‐RHI; atherosclerosis also discriminated RHI‐CCS group (Table 3).ConclusionThese results support vascular and white matter pathologies, specifically white matter rarefaction, as prominent and clinically relevant sequelae of RHI from CCS.

Experimental studies of CFRP laminates under repetitive low-velocity impact loading

Due to their exceptional properties such as high strength-to-weight ratio and fatigue tolerance, laminated composites are widely used in aircraft structures. When subjected to impact loading, composite structures experience intra/inter-laminar damages, and it is crucial to investigate the effect of damages on the strength of the laminate. Single and multiple impact tests are performed on CFRP laminates with different stacking sequences. Cross-ply [0/90]4S and quasi-isotropic [45/90/-45/0]2S laminates are fabricated and tested. Damage size as a function of the number of impacts and impact energy for different stacking sequences are studied. The damage configuration of impacted specimens is studied using the immersion ultrasonic technique. Damage size and shape of multiple impacted specimens are compared with single impacted specimens.

Evolving brain and behaviour changes in rats following repetitive subconcussive head impacts.

There is growing concern that repetitive subconcussive head impacts, independent of concussion, alter brain structure and function, and may disproportionately affect the developing brain. Animal studies of repetitive subconcussive head impacts are needed to begin to characterize the pathological basis and mechanisms underlying imaging and functional effects of repetitive subconcussive head impacts seen in humans. Since repetitive subconcussive head impacts have been largely unexplored in animals, we aimed to characterize the evolution of imaging, behavioural and pathological effects of repetitive subconcussive head impacts in awake adolescent rodents. Awake male and female Sprague Dawley rats (postnatal Day 35) received 140 closed-head impacts over the course of a week. Impacted and sham-impacted animals were restrained in a plastic cone, and unrestrained control animals were included to account for effects of restraint and normal development. Animals (n = 43) underwent repeated diffusion tensor imaging prior to and over 1 month following the final impact. A separate cohort (n = 53) was assessed behaviourally for fine motor control, emotional-affective behaviour and memory at acute and chronic time points. Histological and immunohistochemical analyses, which were exploratory in nature due to smaller sample sizes, were completed at 1 month following the final impact. All animals tolerated the protocol with no overt changes in behaviour or stigmata of traumatic brain injury, such as alteration of consciousness, intracranial haemorrhage or skull fracture. We detected longitudinal, sex-dependent diffusion tensor imaging changes (fractional anisotropy and axial diffusivity decline) in corpus callosum and external capsule of repetitive subconcussive head impact animals, which diverged from both sham and control. Compared to sham animals, repetitive subconcussive head impact animals exhibited acute but transient mild motor deficits. Repetitive subconcussive head impact animals also exhibited chronic anxiety and spatial memory impairment that differed from the control animals, but these effects were not different from those seen in the sham condition. We observed trends in the data for thinning of the corpus callosum as well as regions with elevated Iba-1 in the corpus callosum and cerebral white matter among repetitive subconcussive head impact animals. While replication with larger study samples is needed, our findings suggest that subconcussive head impacts cause microstructural tissue changes in the developing rat brain, which are detectable with diffusion tensor imaging, with suggestion of correlates in tissue pathology and behaviour. The results point to potential mechanisms underpinning consequences of subconcussive head impacts that have been described in humans. The congruence of our imaging findings with human subconcussive head impacts suggests that neuroimaging could serve as a translational bridge to advance study of injury mechanisms and development of interventions.

Learning by Redoing: An Experimental Study on the Impact of Repetition of Formative Assessments in a Formal Methods Course for Software Engineers

Learning by Redoing: An Experimental Study on the Impact of Repetition of Formative Assessments in a Formal Methods Course for Software Engineers

Prevalence of De-Quervain’s Tenosynovitis in Female Tailors in District Wazirabad

Purpose: De Quervain's tenosynovitis affects the thumb abductors close to the radiostyloid process, causes a painful wrist complaint. When performing particular jobs incorrectly, the wrist and thumb might lead to De Quervain's Tenosynovitis. It is associated with work that necessitates repetitive wrist and thumb motion. Pain, numbness, tingling, burning, stiffness, and exhaustion are a few of the warning signs and symptoms. Complaints include a loss of normal sensation, a restriction in range of motion, and a decline in grip strength. The objective of the study was to determine the prevalence of De-Quervain's Tenosynovitis in female tailors in district Wazirabad.
 Methodology: Amongst female tailors, a cross-sectional survey was done. Based on the inclusion and exclusion criteria, 289 participants were chosen through convenient sampling technique. The process was described to the study participants. The degree of the pain was evaluated using the Numeric Pain Rating Scale (NPRS), and an assessment of the illness was made using the Finkelstein test. Both hands were put to use for the test. Pain over the abductor pollicis longus and extensor pollicis brevis tendons at the wrist is a sign of a positive diagnosis. The SPSS program was used to examine the data. Data was presented in for of tables and charts.
 Findings: De-Quervain's Tenosynovitis was present in 43% of the population overall. When the results of the right and left hands were compared, it was discovered that 33% females had right hand had De Quervain's tenosynovitis and 10% had it in both hands. Sixty of the respondents reported experiencing mild pain, 41 women reported moderate pain, and 23 reported severe pain. This study concluded that the prevalence of De-Quervain’s Tenosynovitis in female tailors is low.
 Recommendations: The study was grounded in the Cumulative Stress Theory, emphasizing repetitive motion's impact on occupational health. Tailors should receive training on ergonomics, use ergonomic tools, and undergo regular wrist health check-ups. Policy makers must set occupational health standards for tailors, ensuring ergonomic tool usage, and mandate periodic health audits in tailoring establishments

Quantification of damage expansion influence on frequency response function of plate for structural health monitoring with integral differential method

This paper presents a feasibility study on damage size quantification throughout the damage expansion procedure using the integral differential method based on the developed frequency response function (FRF) programme. A designed pattern of piezoelectric Micro Fibre Composite (MFC) transducers was integrated with three composite panels for a real time monitoring testing by swept sine vibration input signals under three varied frequency bandwidths ranged from 10 to 1 kHz, 1k-3 kHz and 3k-5 kHz, respectively. The composite panels under pristine stage without any impact damages were tested and documented as a cross-reference for subsequent quantification estimation. The damages were introduced around transducers array, and its expansion process is equivalently simulated by a repetitive impact test procedure. A modified damage index, difference of response (DoR), was derived through integral differential method to assess the FRF outcome change of damaged composite plate relative to the pristine state. Combined with damage geometrical dimensions measured by thermography imaging technology, a quantification formula is derived reversely through numerical analysis, which showed a segmentation linear relation between the DoR and damage size governed by the power and logarithmic functions. The damages under different severity subjected to an additional composite plate were successfully quantified by the segmentation formula, which validate the feasibility of quantification with DoR.

Investigating the behavior of hollow steel section beam under repetitive transverse impact loading

When a load is exerted on a structural element several times, it is called repetitive loading. This type of loading causes more damage to structural elements than monotonic loading. This paper presents the effects of repetitive transverse impact loading on the weak axis of rectangular hollow steel section beam. For this purpose, three simply supported beams were tested with a constant drop weight of 75 kg and three different heights (400 mm, 800 mm and 1200 mm). Transverse impact load was exerted on each specimen 3 times repeatedly. In the numerical studies, finite element models of all specimens were developed using ABAQUS finite element analysis software. In order to obtain reliable numerical models, finite element models were verified using the experimental data. To investigate the effects of repetitive transverse impact loading on hollow section steel beam, parameters such as displacement, reaction forces, stress distributions and out of plane plastic denting were evaluated comparatively. The obtained results showed that, when the height value is increased twice as the initial height in test series RIA and RIB, the displacement value increased by 57% in the first hit, 68% in the second hit and 79 % in the third hit. Thus, it seems that the increase in the displacement value due to the increase in the damage of subsequent hits is not linear, but rather logarithmic. Finally, it was understood that with increase in the plastic deformation and displacement occurring in an element subjected to repeated impact loading, a decrement occurs in the reaction force transferred to the supports.

Repetitive Head Impacts In Youth Tackle Football: First Year Athletes Compared To Experienced Athletes

Repetitive Head Impacts In Youth Tackle Football: First Year Athletes Compared To Experienced Athletes

Damage analysis of Nomex honeycomb sandwich structures using image processing and artificial intelligence approaches

AbstractIn this study, a method was developed to detect impact damage and determine the damage propagation in increasing and repetitive impacts. The effect of nanographene additives on the propagation of delamination damage in the top face layer of a sandwich structure was investigated using the developed method. In addition, the effects of nanographene on visible (VID) or barely visible damage (BVID) formation were investigated, and the stiffness of the sandwich structures was evaluated. An ultrasonic C‐scan nondestructive testing was used to visualize the damage, and the numerical values of the damaged areas of the sandwich structures at different energy levels were determined using an image processing method. The obtained values were used in artificial neural network (ANN) training to estimate the impact energy at which the structural integrity of the sandwich structures was disrupted. It was observed that the nanographene additive was effective in maintaining rigidity of the sandwich structures and therefore, slowed the delamination damage progression in increasing and repeated impacts. The damage areas of the neat sandwich structures (NSS) and graphene nanoplatelets doped sandwich structures (GSS) structures at the first impact 5j energy level was 1004 and 811 mm2, respectively. At the first impact, 20% less damage occurred in the GNP‐doped sandwich structures. The increasing and repetitive last impact energies at the end of the neural network training were 5j + 35j in NSS and 5j + 50j in GSS. The method allows for a detailed examination of the damage progression of sandwich structures under increasing and repeated impact loads.Highlights Low‐velocity impact tests of Nomex honeycomb sandwich structures were performed. Damage formation and propagation in sandwich structures were investigated. The non‐destructive test C‐scan method was used to determine BVID. The damaged areas were determined using an image processing method. The damage areas were estimated using artificial neural networks.

Neuropathologic and Clinical Findings in Young Contact Sport Athletes Exposed to Repetitive Head Impacts

Young contact sport athletes may be at risk for long-term neuropathologic disorders, including chronic traumatic encephalopathy (CTE). To characterize the neuropathologic and clinical symptoms of young brain donors who were contact sport athletes. This case series analyzes findings from 152 of 156 brain donors younger than 30 years identified through the Understanding Neurologic Injury and Traumatic Encephalopathy (UNITE) Brain Bank who donated their brains from February 1, 2008, to September 31, 2022. Neuropathologic evaluations, retrospective telephone clinical assessments, and online questionnaires with informants were performed blinded. Data analysis was conducted between August 2021 and June 2023. Repetitive head impacts from contact sports. Gross and microscopic neuropathologic assessment, including diagnosis of CTE, based on defined diagnostic criteria; and informant-reported athletic history and informant-completed scales that assess cognitive symptoms, mood disturbances, and neurobehavioral dysregulation. Among the 152 deceased contact sports participants (mean [SD] age, 22.97 [4.31] years; 141 [92.8%] male) included in the study, CTE was diagnosed in 63 (41.4%; median [IQR] age, 26 [24-27] years). Of the 63 brain donors diagnosed with CTE, 60 (95.2%) were diagnosed with mild CTE (stages I or II). Brain donors who had CTE were more likely to be older (mean difference, 3.92 years; 95% CI, 2.74-5.10 years) Of the 63 athletes with CTE, 45 (71.4%) were men who played amateur sports, including American football, ice hockey, soccer, rugby, and wrestling; 1 woman with CTE played collegiate soccer. For those who played football, duration of playing career was significantly longer in those with vs without CTE (mean difference, 2.81 years; 95% CI, 1.15-4.48 years). Athletes with CTE had more ventricular dilatation, cavum septum pellucidum, thalamic notching, and perivascular pigment-laden macrophages in the frontal white matter than those without CTE. Cognitive and neurobehavioral symptoms were frequent among all brain donors. Suicide was the most common cause of death, followed by unintentional overdose; there were no differences in cause of death or clinical symptoms based on CTE status. This case series found that young brain donors exposed to repetitive head impacts were highly symptomatic regardless of CTE status, and the causes of symptoms in this sample are likely multifactorial. Future studies that include young brain donors unexposed to repetitive head impacts are needed to clarify the association among exposure, white matter and microvascular pathologic findings, CTE, and clinical symptoms.

The Longitudinal Relationship Between Concussion History, Years of American Football Participation, and Alcohol Use Among Former National Football League Players: an NFL-LONG Study.

Investigate the relationships between concussion history and years of football participation (repetitive head impact proxy) with alcohol use across multiple decades in former professional football players. Participants (n= 348; mean age = 49.0 ± 9.4) completed health questionnaires in 2001 and 2019, which included self-reported concussion history and years of participation. Alcohol use frequency and amount per occasion were reported for three timepoints: during professional career, 2001, and 2019. Ordinal logistic regression models were fit to test associations of concussion history and years of participation with alcohol use at each timepoint. There were no significant associations between either concussion history or years of football participation with alcohol use (frequency and amount per occasion) at any timepoint. Effect estimates for concussion history and years of football participation with alcohol use were generally comparable across timepoints. Later life alcohol use by former American football players is not associated with concussion history or years of exposure to football.

Motivated to vote? The effect of flooding on political participation.

This paper investigates changes in political participation following a disaster. Drawing on the electoral results and flood declarations after the 2010 flood in Slovakia, a dataset was constructed that illustrates when and how often each municipality was affected by disastrous conditions before the elections. The analysis revealed that experiencing a flood significantly increased the level of political participation in a municipality. However, the effect of flooding on elections is conditional. First, significantly higher turnout occurs only when a flood affects the municipality on election day. Second, repeated flooding before the elections does not change the overall participation rate. In contrast, it is the one-time, continuous extreme weather event that most mobilises voters. Third, only severely affected municipalities demonstrated a significant turnout effect. Lastly, the timing variable is crucial in determining the impact of repetition and severity. This paper distinguishes between different kinds of flood events that can influence disaster behaviour.

Subjective and Performance-Based Cognition and Their Associations with Head Injury History in Older Former National Football League Players.

Investigate the association between self-reported subjective and performance-based cognition among older (50-70 years) former professional American football players, as well as the relationship of cognitive measures with concussion history and years of football participation, as a proxy for repetitive head impact exposure. Among older former National Football League (NFL) players ( N = 172; mean age = 60.69 ± 5.64), associations of subjective (Patient Reported Outcome Measurement Information System Cognitive Function-Short Form) and performance-based cognitive measures (Brief Test of Adult Cognition by Telephone [BTACT] Executive Function and Episodic Memory indices) were assessed via univariable and multivariable regression models, with a priori covariates of depression and race. A similar univariate and multivariable regression approach assessed associations between concussion history and years of football participation with subjective and performance-based cognitive measures. In a sample subset ( n = 114), stability of subjective cognitive rating was assessed via partial correlation. Subjective ratings of cognition were significantly associated with performance-based assessment, with moderate effect sizes (episodic memory ηp2 = 0.12; executive function ηp2 = 0.178). These associations were weakened, but remained significant ( P s < 0.05), with the inclusion of covariates. Greater concussion history was associated with lower subjective cognitive function ( ηp2 = 0.114, P < 0.001), but not performance-based cognition. The strength of association between concussion history and subjective cognition was substantially weakened with inclusion of covariates ( ηp2 = 0.057). Years of participation were not associated with measures of subjective or objective cognition ( P s > 0.05). These findings reinforce the importance of comprehensive evaluation reflecting both subjective and objective measures of cognition, as well as the consideration of patient-specific factors, as part of a comprehensive neurobehavioral and health assessment of older former contact sport athletes.

Tau Positron Emission Tomography and Neurocognitive Function Among Former Professional American-Style Football Players.

American-style football (ASF) players experience repetitive head impacts that may result in chronic traumatic encephalopathy neuropathological change (CTE-NC). At present, a definitive diagnosis of CTE-NC requires the identification of localized hyperphosphorylated Tau (p-Tau) after death via immunohistochemistry. Some studies suggest that positron emission tomography (PET) with the radiotracer [18F]-Flortaucipir (FTP) may be capable of detecting p-Tau and thus establishing a diagnosis of CTE-NC among living former ASF players. To assess associations between FTP, football exposure, and objective neuropsychological measures among former professional ASF players, we conducted a study that compared former professional ASF players with age-matched male control participants without repetitive head impact exposure. Former ASF players and male controls underwent structural magnetic resonance imaging and PET using FTP for p-Tau and [11C]-PiB for amyloid-β. Former players underwent neuropsychological testing. The ASF exposure was quantified as age at first exposure, professional career duration, concussion signs and symptoms burden, and total years of any football play. Neuropsychological testing included measures of memory, executive functioning, and depression symptom severity. P-Tau was quantified as FTP standardized uptake value ratios (SUVR) and [11C]-PiB by distribution volume ratios (DVR) using cerebellar grey matter as the reference region. There were no significant differences in [18F]-FTP uptake among former ASF players (n = 27, age = 50 ± 7 years) compared with control participants (n = 11, age = 55 ± 4 years), nor did any participant have significant amyloid-β burden. Among ASF participants, there were no associations between objective measures of neurocognitive functioning and [18F]-FTP uptake. There was a marginally significant difference, however, between [18F]-FTP uptake isolated to the entorhinal cortex among players in age-, position-, and race-adjusted models (p = 0.05) that may represent an area of future investigation. The absence of increased [18F]-FTP uptake in brain regions previously implicated in CTE among former professional ASF players compared with controls questions the utility of [18F]-FTP PET for clinical evaluation in this population.

Single Neuron Modeling Identifies Potassium Channel Modulation as Potential Target for Repetitive Head Impacts.

Traumatic brain injury (TBI) and repetitive head impacts can result in a wide range of neurological symptoms. Despite being the most common neurological disorder in the world, repeat head impacts and TBI do not have any FDA-approved treatments. Single neuron modeling allows researchers to extrapolate cellular changes in individual neurons based on experimental data. We recently characterized a model of high frequency head impact (HFHI) with a phenotype of cognitive deficits associated with decreases in neuronal excitability of CA1 neurons and synaptic changes. While the synaptic changes have been interrogated in vivo, the cause and potential therapeutic targets of hypoexcitability following repetitive head impacts are unknown. Here, we generated in silico models of CA1 pyramidal neurons from current clamp data of control mice and mice that sustained HFHI. We use a directed evolution algorithm with a crowding penalty to generate a large and unbiased population of plausible models for each group that approximated the experimental features. The HFHI neuron model population showed decreased voltage gated sodium conductance and a general increase in potassium channel conductance. We used partial least squares regression analysis to identify combinations of channels that may account for CA1 hypoexcitability after HFHI. The hypoexcitability phenotype in models was linked to A- and M-type potassium channels in combination, but not by any single channel correlations. We provide an open access set of CA1 pyramidal neuron models for both control and HFHI conditions that can be used to predict the effects of pharmacological interventions in TBI models.

Suicide and depression in former contact sports participants: population-based cohort study, systematic review, and meta-analysis.

Former participants in sports characterised by low intensity repetitive head impact appear to have elevated rates of later dementia, but links with other psychological health outcomes such as depression and suicide are uncertain. We quantified the occurrence of these endpoints in former contact sports athletes against general population controls using new data from a cohort study and a meta-analysis. The cohort study comprised 2004 retired male athletes, who had competed internationally as amateurs for Finland across a range of sports, and 1385 general population controls. All study members were linked to mortality and hospitalisation registries. In the PROSPERO-registered systematic review (CRD42022352780), we searched PubMed and Embase to October 31 2022 for cohort studies that reported standard estimates of association and precision. Study-specific estimates were aggregated in a random-effect meta-analysis. The Newcastle-Ottawa Scale was used to appraise the quality of each study. In survival analyses of the Finnish cohort data, former boxers (depression: hazard ratio 1.43 [95% CI 0.73, 2.78]; suicide: 1.75 [0.64, 4.38]), Olympic-style wrestlers (depression: 0.94 [0.44, 2.00]; suicide: 1.60 [0.64, 3.99]), and soccer players (depression: 0.62 [0.26, 1.48]; suicide: 0.50 [0.11, 2.16]) did not have statistically higher rates of major depressive disorder or suicide at follow-up relative to controls. In the systematic review, 7 cohort studies met inclusion criteria. After aggregating results with the Finnish cohort, retired soccer players appeared to have a lower risk of depression (summary risk ratio: 0.71 [0.54, 0.93]) relative to general population controls, while the rate of suicide was statistically the same across groups (0.70 [0.40, 1.23]). Past participation in American football seemed to be associated with some protection against suicide (0.58 [0.43, 0.80]) but there were insufficient studies of depression in this sport to facilitate aggregation. The aggregation of results from the soccer and American football studies showed directionally consistent relationships and there was no indication of inter-study heterogeneity (I2=0%). Based on a small cluster of studies exclusively comprising men, retired soccer players had a lower rate of later depression and former American football players had a lower risk of suicide relative to comparator groups. Whether these findings are generalisable to women requires testing. The preparation of this manuscript was unfunded.