A study published in Brain Communications looks at cognitive ability in survivors of mild COVID-19.
Dr Stephen Burgess, statistician, MRC Biostatistics Unit, University of Cambridge, said:
“This is a small study of young adults comparing those who had previous self-reported mild COVID-19 (usually confirmed by PCR test) against those who had no reported COVID-19 (individuals with severe symptoms or signs of “long COVID” were excluded from analyses).
“The exposure was not assigned randomly, it was not blinded from participants, and it may associate with various confounding factors, such as lifestyle and social position. At all stages of the pandemic, there are likely to be many systematic differences on average between individuals who had a positive COVID-19 test versus those who did not. Indeed, there were differences observed in physical fatigue and forgetfulness levels between the COVID and non-COVID groups at baseline, and a higher proportion of those in the COVID group were university educated, although none of these differences reached the evidential threshold for statistical significance.
“However, despite this, differences between the COVID and non-COVID groups in terms of several specific measures of cognitive ability looked at in this study were striking, particularly in terms of delayed memory tasks and ability to perform tasks accurately when fatigued. 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. Additionally, a dose-response relationship was observed, whereby reduction in cognitive ability was inversely associated with time since COVID-19 infection. No discernible difference in cognitive ability was observed 6-9 months after infection, although evidence for this finding is based on a very small number of individuals.
“In conclusion, while further, larger studies are required to provide confirmation, this study raises the possibility that COVID-19 infection could be a causal factor for these measures of reduced cognitive ability in some people, at least in the short- to medium-term following infection.”
‘Rapid vigilance and episodic memory decrements in COVID-19 survivors’ by Sijia Zhao et al. was published in Brain Communications at 00:01 UK time on Wednesday 19 January 2022.
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Dr Stephen Burgess: “No conflict of interest to declare.”