More than one in ten people who catch COVID don’t fully recover — developing a chronic condition called Long COVID which causes a variety of debilitating symptoms, including brain fog. Since some studies have found that COVID infections are associated with overall brain shrinkage, altered brain structure, and an increased risk of developing Alzheimer’s, researchers have been investigating the links between COVID and Alzheimer’s.

Mild

Cognitive problems are common after acute SARS-CoV-2 infection and can be disabling and frightening Symptoms tend to improve, but this may take up to a year. Those with chronically persistent symptoms lasting more than 12 months have a lower chance of improving Symptoms usually fluctuate Assessment should be directed to documenting the nature and trajectory of the impairment and excluding alternative diagnoses Self-management techniques may help patients manage their condition As of March 2023, when the Office for National Statistics stopped collecting data on this condition, 1.879 million individuals had self-assessed as having long covid—symptoms lasting more than 12 weeks following acute covid-19 infection. Of these, the proportion of individuals with symptoms lasting two years or more is around 42%, suggesting a decline in new cases of long covid but a persistence of those with ongoing symptoms.1 Some systematic reviews and meta-analyses have reported that up to a third of such individuals have persistent symptoms of cognitive impairment,23 but estimates vary widely and are complicated by methodological heterogeneity—eg, study size, assessment approach, follow-up duration, and different sampling frames (from self-reported surveys4 to large retrospective matched cohort studies of health records5), as discussed in a recent meta-analysis.6 The pathological underpinnings and potential therapeutic possibilities for cognitive impairment in long covid are also uncertain. The bulk of evidence to date is mechanistic (using basic science, animal models, or human tissue), observational (using longitudinal cohort studies), or hypothetical (reasoning from basic principles); this literature has been well summarised by the RECOVER Consortium.7 Because of the methodological heterogeneity, even when individual studies have been rigorously conducted, it is difficult to know to what extent their findings can be extrapolated and generalised across those with long covid. A few randomised controlled trials of potential treatments (pharmacological and non-pharmacological) have been completed, and others are under way.7 Cognitive performance is typically conceptualised in terms of functional domains depending upon the task at hand. Domains are hierarchical and inter-related, ranging from more basic sensory and perceptual processes to executive functioning and cognitive control.8 Both psychometric studies and qualitative studies of the patient experience identify problems across one or more of these domains. The most frequent symptoms seem to affect memory, attention, and concentration9 but discrete impairments are also seen in attentional and executive processing,1011 different types of memory,1012 visuospatial processing,13 and language.12 Many patients show deficits in multiple domains,1214 which may or may not correlate with self-reported symptoms.15 Moreover, linked systemic symptoms such as fatigue, insomnia, and a general befuddled state frequently termed “brain fog” are commonly reported. This seems to wax and wane with physical fatigue.16 A higher symptom burden is often associated with concomitant mood disorders or post-traumatic stress disorder, regardless of illness severity.15171819 Longitudinal cohort, case control, and qualitative studies have shown that while many individuals improve gradually over time, cognitive symptoms fluctuate unpredictably, causing uncertainty and (in some) anxiety.9202122 These impairments can have profound impacts on an individual’s life, with significant ramifications for relationships, jobs, and normal daily activities.422 This article explores the impact of these symptoms and offers a practical guide for GPs to help them approach cognitive dysfunction in individuals with long covid as indicated by the evolving and conflicting evidence base. An account from a patient’s perspective is given in box 1. Box 1 Patient experience When I got covid in December 2020 I was worried about what might happen. It was before vaccines, and the news was full of statistics of the hospitalised and those who’d lost their lives. After my 14 day isolation I was relieved to get back to normal life, thinking I had dodged quite a bullet. I was quickly aware that something wasn’t right. At the time of my infection I was a drama teacher in a secondary school. I remember being at work in January 2021 and finding it impossible to concentrate on what I had to do. Trying to focus made my head spin, and working on a computer screen was almost impossible. In the classroom I couldn’t process what was happening around me like I used to be able to, there was a sharpness lost, and that had a significant impact on both my teaching ability and classroom management. After several attempts at returning to work it became clear that I wasn’t able to continue, and I left teaching in January 2022. Alongside my difficulties focusing there are problems with memory. Remembering things from one minute to the next is often diff

In a group of Norwegian participants assessed between March 2020 and April 2023, participant-reported memory function, as scored on the EMQ, was numerically worse at several time points up to 36 months after a positive SARS-CoV-2 test than after a negative test.

Mounting research shows that COVID-19 leaves its mark on the brain, including significant drops in IQ scores

neuroinflammation is independent of disease severity and may be one of the main causes of neurological disorders associated with COVID-19. She points out that even patients with milder cases showed significant changes in the CSF, suggesting that the body's inflammatory response may affect the brain in ways not yet fully understood.

Our pilot data suggests that mild COVID-19 may result in brain pathology and impact neurocognitive function in younger adults in a manner parallel to prior findings in older individuals. Though findings may not generalize to other SARS-CoV-2 variants, larger longitudinal studies of mild COVID-19 should be undertaken to understand the potential clinical implications of these findings over the longer term.