Some people have an elevated risk of developing neurological conditions including dementia, cognitive deficit ‘brain fog’ and seizures for two years after COVID-19 infection compared to other respiratory infections, an Oxford University study has shown.

Results of an observational study of more than 1.25 million health records for patients with confirmed SARS-CoV-2 showed that while there was a transient increased risk of depression and anxiety in adults lasting less than two months, the risks of some neurological conditions persisted beyond six months with some strains of the coronavirus.

Published in The Lancet Psychiatry (link) the results showed that adults aged 18-64 who had COVID-19 up to two years previously had a higher risk of cognitive deficit (640 cases per 10,000 people), and muscle disease (44 cases per 10,000), compared to those who had other respiratory infections up to two years previously (550 cases per 10,000 people of cognitive deficit and 32 cases per 10,000 of muscle disease).

In adults aged 65 and over who had COVID-19 up to two years previously, there was a higher occurrence of cognitive deficit (1,540 cases), dementia (450 cases) and psychotic disorder (85 cases per 10,000 people) compared to those who previously had a different respiratory infection (1,230 cases for cognitive deficit, 330 cases for dementia and 60 cases per 10,000 for psychotic disorder.)

In children, the likelihood of most neurological and psychiatric diagnoses after COVID-19 was lower than in adults. However, they were more likely to be diagnosed with seizures (260 cases per 10,000 children for the COVID-19 group vs 130 cases for the control group) and psychotic disorders (18 vs 6 cases per 10,000 children), over the two years following COVID-19.

Long term risks of neurological and psychiatric diagnoses were not seen with the alpha coronavirus variant, but the delta variant was associated with significantly higher six-month risks of cognitive deficit (38% increased risk), epilepsy or seizures (26% increased risk), and ischaemic strokes (27% increased risk) and a lower risk of dementia (40% decreased risk) when compared to those diagnosed with COVID-19 just before the delta wave. The risks during the omicron wave were similar to those when delta was the dominant variant.

The study investigators emphasised that the overall increased risks of long term neurological conditions were low, but could nevertheless impose an increased burden on the healthcare system even with variants that are less severe in other respects.

“The results have important implications for patients and health services as it suggests new cases of neurological conditions linked to COVID-19 infection are likely to occur for a considerable time after the pandemic has subsided. Our work also highlights the need for more research to understand why this happens after COVID-19, and what can be done to prevent or treat these conditions,” said Professor Paul Harrison of the University of Oxford Department of Psychiatry.

Co-author Dr Max Taquet said the study findings showed that patients and clinicians must remain alert to the possibility of these delayed neurological conditions and healthcare services should be well supported to diagnose and treat them even after the pandemic has subsided.

“It is good news that the higher risk of depression and anxiety diagnoses after COVID-19 is relatively short-lived and there is no increase in the risk of these diagnoses in children. However, it is worrying that some other conditions, such as dementia and seizures, continue to be more frequently diagnosed after COVID-19, even two years later,” he said.

Writing in an accompanying comment (link), Dr Jonathan Rogers and Professor Glyn Lewis from University College London said the findings followed previous studies showing that individuals who have had COVID-19 have substantial deficits on cognitive tests.
“This deficit does indeed seem to translate into an increased risk of a diagnosis of dementia. However, dementia has an insidious onset and the cohort is likely to have had some participants with undiagnosed or subclinical cases at baseline. Although concerning, the findings regarding psychosis and dementia need replication in a cohort in which there is more thorough ascertainment of case status,” they wrote.