Among more than 200 symptoms reported for long COVID, ‘brain fog’ – problems with thinking, understanding, focus and memory – is one of the most widespread and long-lasting.
According to the US Centers for Disease Control and Infection (CDC) SARS-CoV-2 (the virus that causes COVID-19) leads to some or all of the following (which may be mild or severe): fever or chills; cough; shortness of breath or difficulty breathing; fatigue; muscle or body aches; loss of taste or smell; sore throat; headache; congestion or runny nose; nausea or vomiting; diarrhoea. Symptoms usually resolve within 1-2 weeks; but for some, the acute illness is followed by lingering symptoms, a condition termed ‘long COVID’ – which can occur in anyone infected by SARS-CoV-2, whether their initial infection was severe, mild or even asymptomatic.
A 2023 US study published in Nature Reviews Microbiology reported 10% of people experience long COVID following acute infection, with 50-70% of people hospitalised with COVID-19 experiencing lasting symptoms and impacts on heart, lungs, immune system, pancreas, liver, gastrointestinal tract, kidneys, spleen, blood vessels, reproductive and neurological systems.
The UK Office of National Statistics Coronavirus Infection Survey reported almost 3% of the population experiencing long COVID in March 2023 – of these 41% were still experiencing symptoms 2 years after initial infection with SARS- CoV-2. More recently in February 2024, the US CDC noted 6.4% of adults have at some time reported long COVID symptoms.
In a major international study from eClinicalMedicine, 91.8% of the long COVID cohort reported symptoms lasted more than 35 weeks after initial infection. The most common and debilitating were fatigue, breathing issues and cognitive dysfunction or ‘brain fog’ in 85.1%.
A recent study in Scientific Reports found ‘brain fog’ in 89% of patients with long COVID; 77% also reported difficulty concentrating and, when researchers assessed them using the Montreal Cognitive Assessment, they found 46% had mild cognitive dysfunction.
A person with brain fog may have problems with memory, focus, thinking and understanding (as well as experiencing stress and fatigue). Professor Stephen Griffin at UK’s University of Leeds told medicalnewstoday.com: ‘Major issues include lack of recall for names, places and events, as well as general inability to process complex tasks and hold concentration over time.
‘General alertness can also be affected which, combined with intense fatigue experienced by many, can be extremely debilitating for interacting socially or functioning at school or work.’
A study published in the journal Nature using data from the UK Biobank compared patient brain scans before and after COVID-19. Those who suffered a SARS-CoV-2 infection had a reduction in grey matter thickness, markers of tissue damage in olfactory regions and changes in brain volume, as well as slightly lower cognitive abilities than those who had not.
