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9 December 2020

Cognition and COVID-19 – What we know

Nearly a year on from the first outbreak of COVID-19, we still have a lot to learn about how the virus works and affects our health. In this article Operational Scientist, Iona Pickett, explores our current understanding of the neuropsychological consequences of COVID-19, in particular the impact on cognitive function.

Nearly a year on from the first outbreak of COVID-19, we still have a lot to learn about how the virus works and affects our health. It is becoming increasingly clear though that many patients recovering from COVID-19 are also experiencing neurological, psychiatric, and cognitive problems (1-4). These symptoms are estimated to be present in up to a third of COVID-19 patients who have been hospitalised(3,4).These symptoms also appear to persist long after recovery from the initial infection, with detrimental effects on patient quality of life(3, 5-7). With a vaccine on the horizon, and hopefully an end to the pandemic, it is time to start assessing the needs of COVID-19 survivors and providing support for their long-term recovery. This article explores our current understanding of the neuropsychological consequences of COVID-19, in particular the impact on cognitive function.

Cognitive impairment during acute illness

There is increasing evidence that COVID-19 can damage the brain (1, 2, 4, 8-12). Neurological symptoms of COVID-19 include ischaemic stroke, encephalopathy, encephalitis, and peripheral neurological disorders (2,4 8). An estimated 30% of patients with neurological symptoms are also thought to suffer from impaired cognition, with deficits reported in attention, executive function, short term memory, and psychomotor processing (1,3, 9, 10). It is not currently known whether these symptoms are caused by the virus directly attacking neural tissues or are a result of brain damage caused by low oxygen levels or an extreme immune response known as a cytokine storm. There is some evidence that the hippocampus, an area of the brain involved in memory processes, is particularly vulnerable to COVID-19-related damage (10). This may go some way to explaining the presence of enduring memory impairments in COVID-19 survivors. Whilst these symptoms are rare, they are more likely to occur in patients who suffer from acute respiratory distress syndrome (ARDS), require mechanical ventilation or are admitted to ICU (4,13).

Previous research has shown that patients admitted to ICU with respiratory distress are also at higher risk of cognitive impairment (14). Three months after discharge from ICU, 40% of patients had global cognition scores consistent with moderate traumatic brain injury and 26% had scores like patients with mild Alzheimer’s disease, with impairment persisting at 12 months for many patients. Importantly, cognitive impairment was associated with experience and duration of delirium during hospitalization (14). Following evidence from the COVID Symptom Study, Public Health England have recently updated their guidance to recognise delirium as a specific symptom of COVID-19, particularly in elderly populations (15). In light of this, some researchers have predicted that some COVID-19 survivors will experience long-term cognitive dysfunction and decline, creating a “secondary pandemic of neurological disease” (3, 5).

Long COVID and impairment after recovery

While the long-term effects of COVID-19 on cognition aren’t yet fully understood, evidence from early cases are starting to provide crucial insights. Many patients report fatigue and breathlessness long after they have recovered from initial COVID-19 infection, known as “Long COVID”, and evidence suggests that this may be true for cognitive symptoms too (3, 5-7, 12). Preliminary data suggests that recovered COVID-19 patients experiencing fatigue 2-3 months after disease onset also had deficits in executive function and visuospatial processing (6). Impairments in cognitive communication and attention have also been reported in COVID-19 survivors (10, 13).

Long-term cognitive effects are often seen following ICU admission and viral infection, as part of post intensive-care syndrome and post-viral fatigue syndrome, respectively. Both syndromes are associated with worsened physical, cognitive and mental health outcomes persisting beyond the initial illness (13). Up to 80% of patients experiencing ARDS and mechanical ventilation experience post intensive care syndrome, often with impairments in memory, attention and executive function (13, 14). Due to this, the extent to which cognitive impairments are due to the virus itself, rather than ICU admission, is unclear. Nevertheless, with up to a third of patients experiencing cognitive impairment at discharge (3,4), it is likely that many COVID-19 survivors will suffer from cognitive decline.

Mental health in survivors of COVID-19

In addition to neurological effects of COVID-19 on cognition, there is some evidence that poor mental health in COVID-19 survivors may contribute to cognitive impairment. Between one quarter and one third of survivors of the SARS and MERS epidemics, caused by similar viruses to COVID-19, reported symptoms of anxiety, depression, or post-traumatic stress disorder for up to 5 years after acute ICU admission (13).

In COVID-19 survivors, rates of anxiety, depression and PTSD have already been found to be higher than rates in the general population (6, 10, 11). There are also other psychiatric effects of COVID-19 infection, with a UK study reporting altered mental state in 31% of patients. 92% of the patients who acquired a psychiatric diagnosis during COVID-19 hospital admission had no previous history of psychiatric disorder, with new diagnoses including psychosis, neurocognitive dementia-like syndrome, and affective disorder (11).

It is well-established that psychiatric disorders such as depression and anxiety can alter cognition (10), so it is likely that poor mental health in survivors of COVID-19 may also contribute to cognitive impairment and decline.

The impact of COVID-19 on cognition in the wider community

It is not just survivors of COVID-19 which may be at risk of cognitive impairment, as there has been some suggestion that the COVID-19 pandemic has impacted cognition in those who do not contract the disease too. One study found that performance on a test of social cognition was worse following lockdown in the UK, with larger impairments seen in those that experienced greater isolation (16).

There is considerable evidence that the pandemic has been detrimental to our mental health with several large scale studies reporting increased symptoms of anxiety, depression, stress, and sleep disorder following the start of the pandemic (17-19). Given the known impact of poor mental health on cognition, in particular stress, it may be that these symptoms may have contributed to the forgetfulness and lack of attention felt by many people during lockdown. With many of us now working from home and unable to see friends and family, there are also concerns about a lack of cognitive stimulation, which may have particularly detrimental effects to those already suffering from cognitive impairment or decline (3).

There is particular concern for young people with one study reporting 40.4% of Chinese young people reporting psychological problems just 2 weeks after the first COVID outbreak (18). Other researchers have raised concerns about the social and cognitive development of young children who have not been able to attend school and have had limited peer interaction (18).

What now?

As news of an effective vaccine offers hope for an end to the pandemic and a return to normal life, we must endeavour to support those experiencing long-term consequences of the COVID-19 pandemic. Further research is needed to understand cognitive impairment in COVID-19 survivors, and the potentially widespread effects in the general population. Neuropsychological tests will play a key role in this, and Cambridge Cognition are keen to partner with researchers who are undertaking this important work. Take a look at the 2020 Covid-19 and Cognition Grant to find out more.

Summary

Although the underlying mechanisms remain unclear, there is substantial and increasing evidence that COVID-19 survivors are at increased risk of cognitive impairment. Further research is needed to better characterise the nature and progression of cognitive decline in patients with COVID-19 so that effective therapies can be implemented, and patient functioning can be maintained. The effect of long periods of social isolation on cognition in vulnerable populations, such as children and the elderly, should also be considered in order to support these groups as life returns to normal.

Who can I talk to?

If you are a person living with the cognitive impacts of COVID-19, and are looking for advice and support in managing your condition, we would encourage you to speak with your GP. You can also obtain more information from these charities:

Heads Together COVID Support

Mind COVID Support

NHS One You COVID and Anxiety

Long COVID SOS Support

References

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Tags : cognition | covid-19 | cognitive science | cantab research grant

Author portrait

Iona Pickett – Operational Scientist, Cambridge Cognition