Researchers from Oxford University’s Department of Experimental Psychology and Nuffield Department of Clinical Neurosciences have revealed that people who have had mild symptoms of COVID-19 can show ‘degraded attention and memory for up to 6-9 months’.
Whilst it had been understood from previous studies conducted that people have suffered from cognitive symptoms including difficulties in concentrating, forgetfulness and fatigue, from an acute infection of COVID-19, these findings had not been proven amongst milder symptoms of COVID-19. Now researchers have found that this memory loss is consistent amongst people who have shown no other symptoms of long covid and have had asymptomatic to moderate symptoms.
155 participants were recruited for this study of which 136 were included in further analysis. 64 had contracted COVID-19 whilst 91 reported that they have not. Whilst none of the participants had received treatment in intensive care, three participants had been hospitalised and seven had displayed severe COVID-19 symptoms that had affected their ability to carry out day-to-day activities.
Stephen Burgess of the MRC Biostatistics Unit at the University of Cambridge highlighted the small number of people included in the study, also adding that it was not randomised. Despite this he said, “differences between the COVID and non-COVID groups in terms of several specific measures of cognitive ability looked at in this study were striking” and “despite the limitations of non-randomised research, it seems unlikely that these results can be explained by systematic differences between the groups unrelated to COVID infection”.
The study asked participants to complete a number of exercises which would test their memory and cognitive ability. The exercises had a particular focus on cognitive functions considered critical for daily life, such as sustaining attention, memory, planning and semantic reasoning.
A control group on factors including fatigue, forgetfulness, sleep patterns and anxiety were tested against all of the participants who had previously been infected with COVID-19, but they were not significantly different.
The study found that the participants performed well in most of the exercises. Their abilities including working memory and planning showed good results. However, participants performed significantly worse in their episodic memory abilities (up to six months post-COVID infection) and a greater decline in their ability to sustain attention over time (for up to nine months) against those who had not been infected.
Dr Sijia Zhao of the Department of Experimental Psychology said: “What is surprising is that although our COVID-19 survivors did not feel any more symptomatic at the time of testing, they showed degraded attention and memory. Our findings reveal that people can experience some chronic cognitive consequences for months”.
Overall, the results prove that specific cognitive abilities are affected by COVID-19 infection but that after 6-9 months these abilities are not significantly different than normal which demonstrates evidence of recovery over time.
However, it seems that these symptoms do wear off as Professor Masud Hussain has stated, “we still do not understand the mechanisms that cause these cognitive deficits, but it is very encouraging to see that these attention and memory impairments return largely to normal in most people we tested by 6-9 months after infection, who demonstrated good recovery over time”.
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