Long COVID associated with cognitive defects that need to be addressed, study urges

COVID-19 has taken the world by surprise since 2020, affecting millions globally. Due to the uniqueness of the SARS-CoV-2 virus, the virus that causes COVID-19, scientists are following individuals who have been infected to better understand both the short- and long-term effects – particularly the cognitive effects of ‘Long COVID‘. 

An ongoing study from the University of Cambridge and University of Exeter follows patients experiencing cognitive issues associated with long-COVID. The research group’s second report, published in Frontiers in Aging Neuroscience, examines how cognition is impacted by SARS-CoV-2 infection.¹ 

What is Long COVID?

Long COVID is the ongoing illness experienced post-SARS-CoV-2 infection; symptoms are like those experienced during infection and last more than twelve weeks. These lasting symptoms cannot be explained by another ailment or illness.²

It is estimated that long COVID affects approximately 10-25% of individuals who have had COVID-19.^1,3,4 One of the most common symptoms of long COVID is cognitive dysfunction, which has been reported in approximately 70% of long-COVID patients.^3,5,6

To better understand how SARS-CoV-2 infection can affect long-term cognitive functioning, 421 people aged 18+ were included in the study, comparing performance on cognitive tests and lasting symptoms.¹ Both men and women were included in the study, including those who had COVID-19 in the past and those who had not. 

COVID-19 survivors reported reduced cognitive functioning

Of those with ongoing symptoms, approximately 77.8% reported having trouble concentrating, 69% reported brain “fog”, 43.7% reported semantic disfluency – stating an incorrect word – and 59.5% reported difficulty finding the right word while speaking.⁷ 

Of those who had COVID-19 in the past, researchers classified them into the following groups: “Recovered” (those who had recovered with no ongoing symptoms), “Mild/moderate” (individuals experienced mild ongoing symptoms), and “Severe” (individuals experienced severe ongoing symptoms).¹ 

Six cognitive tests were used to evaluate cognitive performance in the following categories: memory, category fluency (the ability to produce words that belong to a specified category), executive function reaction time, and executive function performance. Executive functions include working memory and task switching.

The “Word List Recognition Test” showed participants a list and then asked them to select which words had been on that list. The “Pictorial Associative Memory Test” asked individuals to recall which pictures had been presented together. These tests provided measures of memory.

Researchers also measured the ability to categorize; category fluency was measured by asking participants to type words that fell under a category, for example, “food”. The words they typed would disappear and their accuracy and repetition were measured.

Having COVID-19 may be associated with lasting impaired memory

Using the “Word List Recognition Test”, researchers noticed that those who had had COVID-19 in the past performed significantly weaker than those who had not had COVID-19. They also noticed that the COVID-19 survivors’ reaction time on this task was significantly longer than those who had not had COVID-19. 

Similar observations were made using the pictorial associative memory test; those who had COVID performed slightly worse than the “no COVID” group, however there was no significant impact on reaction time. 

Severe long COVID symptoms associated with worse memory

Those who reported severe ongoing long COVID performed worse on the “Word List Recognition Test”; they reported less correct answers than those who had never had COVID. 

For individuals who had recovered, their reaction time was slower than the “no COVID” group. The “Mild/moderate” long COVID group had a slower reaction time than both the “no COVID” group and the recovered group. 

Dr. Lucy Cheke is senior author of the study and a researcher at the University of Cambridge. She commented, “People think that long COVID is ‘just’ fatigue or a cough, but cognitive issues are the second most common symptom – and our data suggest this is because there is a significant impact on the ability to remember.”⁸ 

Dr. Cheke also brought attention to previous findings that have suggested SARS-CoV-2 affects the brain.⁸ For example, recent studies have suggested that infection may induce loss of gray matter in multiple regions of the brain, including significant loss in the left hemisphere.⁹ 

Initial illness may help predict long COVID cognitive symptoms

The University of Cambridge research group highlighted that those with more severe initial COVID-19 symptoms were more likely to experience severe lasting symptoms compared to those with initially mild symptoms.¹ Initial symptoms are those experienced within the first three weeks of infection.

For example, a more severe headache was linked to slower reaction time on the “Word List Recognition Test” and weakened performance on the pictorial associative memory and category fluency tests. 

Cognitive impairment post-COVID-19 needs to be taken seriously

Approximately 50% of study participants struggling with lasting cognitive impairments reported that they encountered difficulty getting healthcare professionals to consider their condition seriously. 75% reported having to take time off from work due to their persisting long COVID symptoms. 

“Long COVID has received very little attention politically or medically. It urgently needs to be taken more seriously, and cognitive issues are an important part of this. When politicians talk about ‘Living with COVID’ – that is, unmitigated infection, this is something they ignore. The impact on the working population could be huge,” said Dr. Cheke.⁹

Results are limited to the original strain and the alpha variant

Only people who had been infected by the original or alpha variant of SARS-CoV-2 were included in this study. Currently, the study is recruiting individuals who have been infected by the Omicron and Delta variants.¹

Hopefully extending the study to include alternate variants will help researchers better understand the cognitive impacts and how healthcare providers can best help individuals recover.

References

1. Guo, P. et al. (2022). COVCOG 2: Cognitive and Memory Deficits in Long COVID: A Second Publication From the COVID and Cognition Study. Frontiers in Aging Neuroscience. Doi: 10.3389/fnagi.2022.804937.
2. COVID-19 Rapid Guideline: Managing The Long-Term Effects of COVID-19. (2020). National Institute for Health and Care Excellence. Retrieved from https://www.nice.org.uk/guidance/ng1889.
3. Cirulli, E. et al. (2020). Long-term COVID-19 symptoms in a large unselected population. medRxiv [preprint]. doi: 10.1101/2020.10.07.20208702.
4. Ding, X.,et al. (2020). Chest CT findings of COVID-19 pneumonia by duration of symptoms. European Journal of Radiology; 127 (109009). doi: 10.1016/j.ejrad.2020.109009.
5. Bliddal, S. et al. (2021). Acute and persistent symptoms in non-hospitalized PCR-confirmed COVID-19 patients. Scientific Reports; 11(13152). doi: 10.1038/s41598-021-92045-x.
6. Davis, H. E., et al. (2021). Characterizing long COVID in an international cohort: 7 months of symptoms and their impact. EClinical Medicine; 38(101019). doi: 10.1016/j.eclinm.2021.101019.
7. Guo, P. et al. (2022). COVCOG 1: factors predicting cognitive symptoms in Long COVID. A first publication from the COVID and Cognition Study. Frontiers in Aging Neuroscience. doi: 10.3389/fnagi.2022.804922.
8. Garget, Jacqueline. (2022). Memory and concentration problems are common in ling COVID and must not be ignored, says scientists. EurekAlert! Accessed Mar. 23, 2022. Retrieved from https://www.eurekalert.org/news-releases/946155. 
9. Douaud, G. et al. (2021). Brain imaging before and after COVID-19 in UK Biobank. medRxiv [preprint]. doi: 10.1101/2021.06.11.21258690.

Image by Gerd Altmann from Pixabay