Kognitivni evocirani potencijali, kognitivna rezerva i kvalitet spavanja kao neurofiziološki pokazatelji kognitivnog stanja osoba starije životne dobi

Abstract

Uvod. Imajući u vidu globalni trend produženja životnog veka i važnost očuvanja kognitivnih sposobnosti tokom starenja, nameće se potreba za utvrđivanjem značaja svih potencijalnih činioca koji mogu da utiču na trend kognitivnog opadanja tokom starenja. Metoda kognitivno-evociranih potencijala (KEP), a posebno P300 talas se već duže vremena primenjuju u proceni kognitivnog stanja osoba pri čemu se smatra da latencija P300 talasa ukazuje na brzinu kognitivne obrade stimulusa a njegova amplituda na stepen angažovanosti resursa pažnje. U novije vreme se izdvaja koncept kognitivne rezerve koji se odnosi na veću adaptabilnost kognitivnih procesa kod osoba koje su se više obrazovale, imale odgovornija zanimanja i/ili imale više aktivnosti u slobodno vreme. Veća efikasnost kognitivnih procesa kod ovih osoba može jednim delom da objasni postojanje interindividualnih razlika u kognitivnom opadanju tokom normalnog starenja ali i u slučaju različitih patoloških i traumatskih stanja mozga. Spavanje kod starih osoba je lošijeg kvaliteta a najmarkantnija promena u arhitektonici spavanja tokom starenja je postepena redukcija sporotalasnog spavanja koje je od velikog značaja za poboljšanje kortikalne plastičnosti i povećanje klirensa metaboličkih nusproizvoda. Takođe je dokazano da insomnija i drugi poremećaji spavanja, ispoljavaju negativne efekte na hipokampalnu neurogenezu, funkcije prefrontalnog korteksa kao i na ukupno kognitivno stanje što stvara potrebu za detaljnim izučavanjem međusobne povezanosti starenja, spavanja i kognitivnih funkcija. Cilj. Cilj ovog istraživanja je bio da se utvrde neurofiziološki korelati kognitivnog starenja i da se utvrdi eventualna povezanost kognitivnog stanja sa kognitivnom rezervom i kvalitetom spavanja kod osoba starije životne dobi. Materijal i metode. Istraživanje je osmišljeno kao studija preseka koja je sprovedena na ukupno 106 ispitanika oba pola, starosti 65-80 godina (72±4,46 godina), bez ustanovljenih kognitivnih i neuropsihijatrijskih oboljenja. Korišćenjem standardne auditivne oddball paradigme određeni su parametri kognitivno-evociranih potencijala, odnosno amplituda i latencija P300 talasa iznad Fz i Cz elektrode, izborno reakciono vreme, procenat tačnih odgovora i broj grešaka prilikom testiranja. Kognitivni status ispitanika je dodatno procenjen korišćenjem Montrealske procene kognicije (MoCA) a indeks kognitivne rezerve korišćenjem posebnog upitnika. Za procenu kvaliteta spavanja ispitanika korišćen je Pitsburški indeks kvaliteta spavanja. Pre sprovođenja samog istraživanja na uzorku osoba starije životne dobi, sprovedena je pilot studija na 223 ispitanika starosti 18-85 godina (52,34±18,46 godina), koja je imala za cilj da proceni internu konzistenciju upitnika koji je korišćen za procenu indeksa kognitivne rezerve (CRIq) u ovom istraživanju pri čemu je utvđena njegova dobra pouzdanost (Kronbahov α=0,82). Rezultati. Utvrđena je statistički značajna povezanost latencije i amplitude P300 talasa (p<0,05) sa starošću ispitanika pri čemu se amplituda smanjuje tokom godina a latencija produžava godišnje oko 2,37 ms iznad Fz i 2,12 ms iznad Cz elektrode, što metodu kognitivno-evociranih potencijala čini superiornijom u praćenju kognitivnog starenja od testa Montrealske procene kognicije čiji rezultati nisu bili u korelaciji sa starošću ispitanika (r=-0,141;p=0,150). U okviru ispitivanog uzorka nije utvrđeno postojanje statistički značajne povezanosti ukupnog skora Indeksa kognitivne rezerve sa starošću ispitanika ali je utvđena pozitivna korelacija između subdomena Obrazovanje i starosti (r=0,326,p<0,001). Nije ustanovljena statistički značajna korelacija parametara KEP sa ukupnim CRIq indexom, dok su ustanovljene statistički značajne povezanosti latencije sa domenom Radna Aktivnost i amplitude P300 talasa sa domenom Obrazovanje. Utvrđena je visoko statistički značajna povezanost indeksa kognitivne rezerve sa rezultatima MoCA testa koja je bila umerenog stepena (r=0,434;p<0,001). Na osnovu rezultata Pitsburškog indeksa kvaliteta spavanja (PSQI) ustanovljeno je da su ispitanici u proseku imali nešto lošiji kvalitet spavanja (5,70±3,44) od preporučenih vrednosti (PSQI<5). U okviru ispitivanog uzorka nije utvrđeno postojanje povezanosti starosti ispitanika sa ukupnim PSQI skorom ali je utvrđeno da je lošiji kvalitet spavanja povezan sa nižom relativnom amplitudom P300 talasa iznad Cz elektrode, pri čemu najznačajniju povezanost sa njom pokazuju rezultati sledećih domena PSQI upitnika: Dnevna disfunkcionalnost osobe i Upotreba lekova za spavanje. Ustanovljen je negativan stepen korelacije ukupnog PSQI skora i domena Egzekutivnih funkcija sa MoCA testa (r=-0,196;p<0,05). Trajanje dremanja preko dana je imalo pozitivan smer korelacije sa latencijom P300 talasa iznad verteksa (r=0,210;p<0,05). Rezultati hijerarhijske regresione analize su pokazali da ukupan rezultat MoCA testa ima najznačajniji pojedinačni doprinos predikciji latencije P300 talasa nad obe registrovane elektrode (β≈-0,5;p<0,001), a pojedinačne doprinose predikciji amplitude P300 talasa nad verteksom pokazuju: godine (β=-0,223;p=0,029), CRI-obrazovanje (β=-0,367;p=0,008) i ukupan PSQI skor (β=-0,208;p=0,027). Zaključak. Procena karakteristika P300 talasa, njegove latencije i amplitude daje bolji uvid u kognitivno starenje od Montrealske procene kognicije ali je za kompletnije sagledavanje kognitivnog stanja neophodno komplementarno korišćenje oba instrumenta. Za procenu povezanosti kognitivnog stanja sa kognitivnom rezervom neophodno je sagledavanje pojedinačnih kognitivnih domena i vrednosti svakog pojedinačnog domena značajnog za formiranje kognitivne rezerve: obrazovanje, radna aktivnost i slobodno vreme. Lošije spavanje kod osoba starije životne dobi je povezano sa lošijim egzekutivnim funkcionisanjem a duže dremanje preko dana je povezano sa dužim latencijama P300 talasa.

Introduction. Given the global trend of increasing life expectancy and the importance of preserving cognitive capacities during aging, there is a need to determine the importance of all potential factors that may influence the trend of cognitive decline during aging. The method of event-related potentials (ERP), especially P300 wave, have been used for a long time in assessing of individual's cognitive state and it is believed that P300 wave latency indicates the speed of cognitive stimulus processing and its amplitude the degree of attention resources. Recently, the concept of cognitive reserve stands out, which refers to the greater adaptability of cognitive processes in people who are more educated, had more responsible occupations in life and had greater involvement in leisure activities. Greater efficiency of cognitive processes in these individuals may partly explain the existence of interindividual differences in cognitive decline during normal aging but also in the case of various pathological and traumatic brain conditions. Sleep in the elderly is of poorer quality and the most striking change in sleep architecture during aging is the gradual reduction of slow-wave sleep, which is of great importance for improving cortical plasticity and increasing the clearance of metabolic by-products. Insomnia and other sleep disorders have also been shown to have negative effects on hippocampal neurogenesis, prefrontal cortex functions and overall cognitive state, which creates the need for a detailed study of the interrelationships between aging, sleep, and cognitive function. Aim. The aim of this study was to determine the neurophysiological correlates of cognitive aging and to determine the possible association of cognitive status with cognitive reserve and sleep quality in the elderly. Material and methods. The study was designed as a cross-sectional study conducted on a total of 106 subjects of both genders, aged 65-80 years (72±4.46 years), without established cognitive and neuropsychiatric diseases. Using the standard auditory oddball paradigm, the parameters of event-related potentials were determined, ie the amplitude and latency of P300 waves on Fz and Cz electrode sites, the choice reaction time, the percentage of correct answers and the number of errors during testing. The cognitive status of the respondents was additionally assessed using the Montreal Cognitive Assessment (MoCA) and the cognitive reserve index using a special questionnaire. The Pittsburgh Sleep Quality Index was used to assess the quality of sleep of the respondents. Prior to conducting the survey on a sample of elderly people, a pilot study was conducted on 223 respondents aged 18-85 years (52.34±18.46 years), which aimed to assess the internal consistency of the questionnaire used to assess the index cognitive reserves (CRIq) in this study after which its good reliability was determined (Cronbach's α=0.82). Results. Statistically significant correlation was found between the latency and amplitude of the P300 wave (p<0.05) and the age of the subjects, whereby amplitude decreases during the course of aging and latency increases with a slope of 2.37 ms for Fz and 2.12 ms for Cz electrode site, which makes event-related potentials a method superior in monitoring cognitive aging than the Montreal Cognitive Assessment solely whose results were not correlated with the age of the subjects (r=-0.141;p=0.150). Within the examined sample, there was no statistically significant correlation between the total score of the Cognitive Reserve Index and the age of the respondents, but a positive correlation was found between the subdomain Education and age (r=0.326;p<0.001). No statistically significant correlation of ERP parameters with the total CRIq index was found, while statistically significant correlations of P300 latencies with the domain of WorkingActivities and P300 amplitude with the domain of Education were found. A highly statistically significant correlation was found between the cognitive reserve index and the results of the MoCA test, which was of a moderate degree (r=0.434;p<0.001). Based on the results of the Pittsburgh Sleep Quality Index (PSQI), it was found that the respondents had on average slightly worse sleep quality (5.70±3.44) than the recommended values (PSQI<5). Within the examined sample, there was no correlation between the age of the subjects and the total PSQI score, but it was found that poorer sleep quality was correlated to lower relative P300 amplitudes on the Cz electrode site, while the most significant correlations were between the amplitude and the Daytime dysfunction and the Use of sleeping medication. A negative correlation between the total PSQI score and the domain of Executive Functions on MoCA test was found (r=-0.196;p<0.05). The duration of napping during the day was positively correlated to the P300 latency on the vertex (r=0.210;p<0.05). The results of hierarchical regression analysis showed that the total result of the MoCA test has the most significant individual contribution to the prediction of P300 wave latencies over the both registered electrode sites (β≈-0.5;p<0.001). Individual contributions to the prediction of relative P300 amplitude on the vertex showed: age (β=-0.223;p=0.029), CRI education (β=-0.367;p=0.008) and total PSQI score (β=-0.208;p=0.027). Conclusion. The assessment of the characteristics of the P300 wave, its latency and amplitude gives a better insight into cognitive aging than the Montreal Cognitive Assessment, but for a more detailed understanding of cognitive state, complementary use of both instruments is necessary. To assess the connection between the cognitive state and the cognitive reserve, it is necessary to consider individual cognitive domains and the values of each particular domain important for the formation of cognitive reserve: Education, WorkingActivities and LeisureTime. Poorer sleep in elderly is associated with poorer executive functioning and longer periods of naps during the day are associated with longer P300 wave latencies.