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Changes in cognitive function and cerebral oxygenation patterns in rugby and non-contact sportspersons over a 15-week season

Clark, Anthony (2018-03)

Thesis (MA)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Rugby is a contact team sport and is one of the most popular sports in South Africa and internationally. Recently, a growing body of research has highlighted that repeated concussive and subconcussive head contacts suffered during contact sport participation may have implications on athletes’ health later in life. Of particular concern is the notion that the accumulation of these blows to the head may spark progressive neurodegeneration in the form of diseases such as chronic traumatic encephalopathy (CTE). Despite these concerns, the focus of research in rugby appears to be on the diagnosis and acute treatment of concussive injury, with little thought given to the long-term consequences. The purpose of this study was to broaden our understanding of the effect of short-term exposure to physical contact on the brains of rugby players who participate in high-level contact sport competition. The primary aim of the study was to determine whether a fifteen-week season elicit a change in the cognitive function and cerebral oxygenation of rugby players when compared with age and sex matched non-contact athletes. The secondary aim was to determine whether changes in sleep quantity and quality, as well as mood states, took place that have the potential to impact the cognitive function and cerebral oxygenation of the participants. Twenty-nine university athletes (16 rugby players (21,3 ± 1,35 yrs) and 13 non-contact sport athletes (20,8 ± 1,97 yrs)) were assessed before and after the 2017 Varsity Cup rugby competition (± 15 weeks). Each participant completed the CNS Vital Signs® Core testing battery, with measurements of cerebral oxyhaemoglobin (Δ[O2Hb]), deoxyhaemoglobin (Δ[HHb]), tissue oxygenation index (TOI) and normalised total haemoglobin index (nTHI) conducted simultaneously throughout testing. The cognitive testing battery consisted of seven tests that assessed eleven cognitive domains, giving an overall estimate of cognitive function. Additionally, participants’ mood states and sleep status (quality and quantity) were measured prior to cognitive and cerebral oxygenation analysis each session. Overall, cognitive function did not change for either group over the 15-week season (ES = 0,11 and 0,06 for Rugby and Control, respectively). Cerebral oxygenation measurements did not reflect any unexpected changes within the Control group, however, relative Δ[HHb] (ES = 0,57) and nTHI (P = 0,01; ES = 1,29) were significantly increased at post-testing in the rugby players. These variables are considered indirect indicators of oxygen consumption and cerebral blood flow rate, respectively. Thus, while the rugby players’ cognitive performance was maintained, alterations to cerebral oxygenation data took place that may be the result of participation in their sport. These findings may suggest that subtle impairments are beginning to take place within the brains of the players. Therefore, although a 15-week season may not have been enough to induce obvious negative changes in rugby players’ cognitive function, exposure to contact over the course of multiple seasons may cause neural impairments to the extent that cognitive function, and health, are affected later in life. Despite these notions, it is recognised that changes in mood state and sleep pattern of the players may have confounded the results. Thus, additional research is required to further build on the sentiments proposed in this study.

AFRIKAANSE OPSOMMING: Rugby is ‘n kontak spansport en een van die mees populêre sportsoorte in Suid-Afrika en in die wêreld. Onlangse navorsing wys toenemend daarop dat herhaaldelike kontak teen die kop tydens deelname aan kontaksport, of dit konkussief of sub-konkussief is, mag implikasies inhou vir die gesondheid van atlete in hulle latere jare. Wat veral kommerwekkend is, is die aanspraak dat die voortdurende kontak teen die kop oor jare progressiewe neuro-degenerasie in die vorm van siektes soos kroniese traumatiese enkefalopatie (KTE) mag veroorsaak. Ongeag hierdie bekommernis, blyk dit dat die fokus van navorsing in rugby konsentreer op die diagnose en akute behandeling van harsingskudding en min aandag aan die langtermyn nagevolge. The doel van hierdie studie was om ons begrip oor die effek van korttermyn blootstelling aan fisieke kontak op die breine van rugbyspelers wat aan ‘n hoë vlak kompetisie deelneem, te verbreed. Die primêre doelwit van die studie was om te bepaal of ‘n 15-weke seisoen ‘n verandering in die kognitiewe funksie en serebrale oksigenasie van rugbyspelers veroorsaak, in vergelyking met nie-kontak atlete van dieselfde ouderdom en geslag. Die sekondêre doelwit was om te bepaal of veranderinge in slaap kwantiteit en kwaliteit, asook gemoedstoestand plaasvind, wat die potensiaal het om die kognitiewe funksie en serebrale oksigenasie van deelnemers te beïnvloed. Nege en twinting universiteitvlak atlete (16 rugbyspelers (21,3 ± 1,35 jr) en 13 nie-kontak sport atlete (20,8 ± 1,97 jr)) was voor en na die 2017 Varsitybeker kompetisie ondersoek (+ 15 weke). Elke deelnemer het die CNS Vital Signs® Core toetsbattery afgelê, terwyl metings van serebrale oksihemoglobien (Δ[O2Hb]), deoksihemoglobien (Δ[HHb]), weefesel oksigenasie-indeks (TOI) en genormaliseerde hemoglobienindeks (THI) op dieselfde tyd gemaak is. Die kognitiewe toetsbattery het uit sewe toetse bestaan waarmee elf kognitiewe domeine getoets is en waarna ‘n globale telling vir kognitiewe funksie bereken is. Deelnemers se gemoedstoestand en slaapstatus (kwaliteit en kwantiteit) is ook tydens elke sessie voor die kognitiewe en serebrale oksigenasie analise bepaal. In die geheel was daar geen verandering in kognitiewe funksie oor die 15 weke seisoen in enige van die twee groepe nie (ES = 0,11 en 0,06 vir Rugby en Kontrole, respektiewelik). Daar was geen onverwagse veranderinge in die serebrale oksigenasie metings van die Kontrole groep nie, maar relatiewe Δ[HHb] (ES = 0,57) en nTHI (P = 0,01; ES = 1,29) het betekenisvol verhoog tydens die post-toetsing in die rugbyspelers. Hierdie veranderlikes word as indirekte merkers van onderskeidelik suurstofverbruik en serebrale bloedvloei beskou. Hoewel die kognitiewe funksie van die rugbyspelers onveranderd gebly het, was daar veranderinge in die oksigenasie data wat moontlik toegeskryf kan word aan die deelname aan hulle sport. Hierdie resultate mag dui op die aanvang van subtiele veranderinge in die breine van die spelers. Hoewel die 15 weke seisoen dalk nie genoeg was om opvallende negatiewe veranderinge in die kognitiewe funksie van die rugbyspelers te veroorsaak nie, sal die blootstelling aan kontaksport oor verskeie seisoene neurale veranderinge veroorsaak wat kognitiewe funksie en gesondheid op die lange duur negatief sal beïnvloed. Dit moet egter in gedagte gehou word dat veranderinge in die gemoedstoestand en slaappatrone van die spelers wel die resultate kon beïnvloed het. Meer navorsing is dus nodig om voort te bou op die argumente in hierdie studie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103656
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