Long covid

By July 26, 2021Science

In daily briefings by politicians and their chief medical officers we usually hear a recital of the number of new cases, and how many were in quarantine, in isolation or were in the community while infectious. They also announce any deaths that may have occurred in the previous 24 hours. However, one factor which they do not and probably are unable to report is the number of people with what is termed ‘long covid’.

Surveys of people who have been infected with Covid-19 have found that a significant number of them experience long term effects. A recent survey involved 3762 participants from 56 countries with confirmed or suspected Covid-19 and found that the majority (91%) of respondents had a time to recovery from the disease exceeding 35 weeks. The most frequent symptoms after 6 months were fatigue, post-exertional malaise, and cognitive dysfunction. Cognitive dysfunction or memory issues were common across all age groups and were experienced by 88% of participants. The symptoms span 10 organ systems: neuropsychiatric, systemic, reproductive, cardiovascular, musculoskeletal, immunological, head-ear-eye-nose-throat, pulmonary, gastrointestinal and dermatological. A combination of the neurological-cognitive and systemic symptoms have been shown to persist the longest.1

While the changes in cognition* have been reported, there has been little objective measurement of effects on cognitive abilities and how this varies with the severity of the Covid-19 infection in a large-scale study. Nor have previous studies taken account of social or demographic variables (e.g. age, ethnic group, pre-existing medical conditions, mental health, etc.).2  Another study reported in the Lancet was to determine if there was such an association between Covid-19 infection and cognitive performance data. This study was from 81,337 participants who between January and December 2020 undertook a clinically validated web-optimised assessment as part of the Great British Intelligence Test. Its questionnaire items captured self-reports of suspected and confirmed COVID-19 infection and respiratory symptoms.2

People who had recovered from Covid-19, including those no longer reporting symptoms, exhibited significant cognitive deficits versus controls when controlling for age, gender, education level, income, racial-ethnic group, pre-existing medical disorders, tiredness, depression and anxiety. The deficits were of substantial effect size for people who had been hospitalised (N=192), but also for non-hospitalised cases who had confirmation of Covid-19 infection (N=326). Analysing markers of intelligence did not indicate these differences were present prior to infection.2

As if a decline in cognition after infection with Covid-19 wasn’t enough to worry about, a recent study in Italy has found that about half of the patients admitted to a particular Italian hospital for Covid-19 during the start of the pandemic had developed hyperglycaemia (i.e. high levels of blood sugar). They also had poorer outcomes in the treatment of their Covid-19 infection. The study assessed the health of 551 people admitted to the hospital from March through to May in 2020, with a follow up period extended to six months after hospital admission. The people were not diabetic before infection, but 46% of them were found to have developed hyperglycaemia. While two thirds of those cases returned to normal, one third remained hyperglycaemic for at least six months after Covid-19 infection. It indicates that the pancreas can be damaged by the virus and may affect the long-term health of those infected with Covid-19.3,4  Some researchers are concerned that this may lead to an epidemic of diabetes after the pandemic.3

Given the millions of cases of Covid-19 worldwide and current research showing 14% of Covid-19 patients still symptomatic at 12 weeks, the number of long covid patients is likely to be substantial. The results of these studies suggest long covid often affects multiple organ systems, with significant impacts on morbidity, mortality and quality of life. This also adds to the urgency with which the slowing of the spread of Covid-19 through public health measures and vaccinations must be undertaken and indicates there will be a need for increased sick leave, disability benefits as well as workplace flexibility for sufferers of long covid.1  This will also have a significant economic impact.

*Cognition refers, quite simply, to thinking. This includes everything from what to do when the phone rings, to doing arithmetic or analysing a Shakespearian play, but extends to more subtle things such as interpreting sensory input, guiding physical actions and empathising with others. However, current research into cognition is mostly focused not just on thinking, but also on attention, the creation and storage of memories, knowledge acquisition and retention, language learning, and logical reasoning. As people gain new experiences, their cognition can change significantly.5


  1. https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(21)00299-6/fulltext
  2. https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(21)00324-2/fulltext
  3. https://medicalxpress.com/news/2021-07-diabetes-link-covid-.html
  4. https://www.nature.com/articles/s42255-021-00407-6
  5. https://www.psychologytoday.com/au/basics/cognition


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