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Long Covid diagnosis may mask other illnesses

Long Covid diagnosis may mask other illnesses

People who suffer from an illness prior to a Covid-19 infection are more likely to experience a long illness after the infection, a new study has shown.

Researchers from King’s College London (KCL) found that individuals with illness before Covid-19 infection were almost twice as likely to suffer a long period of illness after infection than individuals who were symptom-free before infection. Post Covid-19 symptoms were found to be related to infection in some cases but were also ongoing manifestations of prior illnesses such as depression and asthma.

The findings are published on the preprint server MedRxiv and are not yet peer-reviewed, but the research has highlighted the need for a fuller exploration of patient history when examining long illness after a Covid-19 infection to ensure post Covid-19 illness and symptoms are treated appropriately.

Most people with Covid-19 recover completely within a few days or weeks. Others experience prolonged illness lasting over eight weeks, reporting ongoing symptoms including fatigue, ‘brain fog’, sneezing, a runny nose and headache long after infection, which may manifest as long Covid.

Using data from the Zoe System Study app, the researchers analysed data from over 23,000 people who tested positive for Covid-19. The participants reported their health at least once a week, before and after infection. Within this group, the researchers identified and assessed 1,350 participants who reported long-term symptoms after Covid- 19. This included individuals with symptoms at eight weeks and nearly 1,000 who had symptoms for more than 12 weeks. This data was compared with 1,350 individuals whose symptoms had resolved within four weeks.

The analysis showed that individuals with symptoms or illness before a Covid-19 infection were significantly more likely to have a lengthier illness duration.

Two-thirds of participants with an extended illness duration were well and healthy before they were infected by Covid-19. However, the remaining one-third, who had shown illness symptoms before infection, were almost twice as likely to experience a long period of illness after infection than those who were not ill before infection.

Lead author Professor Emma Duncan, from KCL, said: ‘Individuals with long symptom duration after SARS-CoV-2 need careful and holistic assessment.  For many, their symptoms are new and represent an ongoing legacy after their Covid-19 illness.  But for others, their symptoms may be ongoing manifestations of a prior non-Covid illness, such as asthma or depression. It is important that these other conditions are not missed, as they have well-established and effective treatments.’

Examining the data further revealed that individuals with long illness duration were also significantly more likely to have prior physical and mental health comorbidities. The researchers suggest that for some individuals, their long symptoms might be due to other underlying serious illnesses, such as asthma or lung disease, rather than due to SARS-CoV-2 infection itself.

Professor Duncan added: ‘If all long duration symptoms after Covid-19 are blamed automatically on SARS-CoV-2 infection, then we will miss the opportunity to treat other illnesses appropriately and to help patients recover as expeditiously as possible.’


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