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Long-COVID is now recognised and accepted as a clinical entity with fatigue, cough, and headache being common symptoms. The National Institute for Health and Care Excellence (NICE) offers guidance for the management of long-COVID, with the NHS providing specialist long-COVID clinics.
In December 2021 the Office for National Statistics (ONS) reported that 1 in 5 people with COVID-19 develop longer term symptoms. Around 186,000 people experience health problems for up to 12 weeks, with the ONS estimating that around 1 in 10 (9.9%) of people who had COVID-19 remained symptomatic after 12 weeks.
In a new study, researchers from Oxford’s Department of Experimental Psychology and Nuffield Department of Clinical Neurosciences described how previous research has demonstrated that after acute COVID-19 infection some people experience persistent cognitive symptoms – fatigue, forgetfulness, and ‘brain fog’ (concentration difficulties) – as part of long-COVID. However, it was not known whether individuals who had mild COVID-19 symptoms, and who report no concerns post-infection, also suffered cognitive impairment. The authors also pointed out that “most research has predominantly focused on symptomatic, hospitalised patients”.
In their study, published in the journal Brain Communications , the researchers set out to answer the question: Do those who had COVID-19 infection, but who had not been hospitalised and do not report any ongoing symptoms after recovery, suffer cognitive deficits that they are not aware of?
To answer their question the researchers asked 136 participants – mean age 28.6 years, 54% female – to complete a series of 12 online cognitive tasks to test their memory and cognitive ability, with a focus on cognitive functions critical for daily life, such as sustaining attention, memory, planning and semantic reasoning. Participants were recruited from the Prolific online recruitment platform, with the study advertised as ‘a brain game’ testing how well people could perform, so that participants were naïve about the aim of the study.
Significantly Worse Episodic Memory and Decline in Sustained Attention
In their study, questionnaire-derived measures – fatigue, forgetfulness, motivation, sleep abnormality, depression and anxiety levels – were no different from age-matched controls. Study participants began with normal behavioural performance, but this was followed by a gradual decline away from age-matched controls, suggesting, say the authors, “reduced ability to attentively track and maintain information over time”.
Dr Sijia Zhao of the Department of Experimental Psychology, University of Oxford, 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.”
In their study the researchers report that the participants performed well in most abilities tested, including working memory and planning, but they displayed significantly worse episodic memory and a greater decline in the ability to sustain attention over than uninfected individuals, with the authors commenting that the significantly worse episodic memory decrement over time was “comparable to a healthy, elderly person in their 60s”.
Dr Zhao commented: “Our findings reveal that people can experience some chronic cognitive consequences for months.”
In the study the authors explained how “COVID-19 survivors showed a significant reduction in their ability to sustain attention on a demanding task up to 9 months after COVID-19 infection, along with mild, but significantly worse, episodic memory for up to 6 months.”
Cognitive Impairment Recovery
The study findings demonstrated how even though people may not report long-COVID symptoms, “chronic cognitive reductions following COVID-19 are evident upon objective testing.”
The authors urged that in future it is important to measure cognitive performance objectively if a better understanding of how the brain is affected by COVID-19 is to be achieved.
Professor Masud Husain of the Nuffield Department of Clinical Neurosciences, University of Oxford, said: “We still do not understand the mechanisms that cause these cognitive deficits, but it is very encouraging to see that these attention and memory return largely to normal in most people we tested by 6-9 months after infection, who demonstrated good recovery over time.”
Créditos: Comité científico Covid