A new study has identified the main factors that make it more likely that patients will suffer long term from the coronavirus.
"Long Covid" is the term given to people who recover from coronavirus but continue to suffer from a wide range of symptoms, such as shortness of breath, migraines and chronic fatigue.
A new analysis by researchers at King's College London, using data from the COVID Symptom Study app, shows that 1 in 20 people with Covid-19 are likely to suffer symptoms for at least eight weeks.
The study, published Wednesday, looked at data from 4,182 users of the COVID Symptom Study app who had tested positive for the virus and had been consistently logging their health.
The team found that older or overweight people, women, those with asthma and those with a greater number of different symptoms in the first week of their illness were more likely to develop "long Covid."
Risk factors
Delving into the risk factors more closely, the study found that long Covid affects around 10% of 18-49 year olds who become unwell with Covid-19, with the percentage rising to 22% for those over 70s.
Weight also plays a role, with it affecting people with a slightly higher average body mass index.
Women were much more likely to suffer from long Covid than men (14.5% compared with 9.5%), but only in the younger age group.
The researchers also found that people reporting a wide range of initial symptoms were more likely to develop long Covid, as were people with asthma, although there were no clear links to any other underlying health conditions.
As for the commonly reported symptoms of long Covid, the research identified two main symptom groupings; One was dominated by respiratory symptoms such as a cough and shortness of breath, fatigue and headaches.
The second grouping "was clearly multi-system, affecting many parts of the body, including the brain, gut and heart," the study said.
Predictive model
The findings are due to be published as a preprint on medRxiv, which distributes unpublished eprints about health sciences and have not been peer reviewed. The researchers have used their findings to develop a model that can predict who is most at risk of long Covid by looking at an individual's age, gender and count of early symptoms.
The lead researchers, Dr. Claire Steves and epidemiologist Tim Spector, said the study could be used to help target early interventions and research aimed at preventing and treating long Covid.
"It's important we use the knowledge we have gained from the first wave in the pandemic to reduce the long-term impact of the second," said Steves, a geriatrician.
"This research could already pave the way for preventative and treatment strategies for long Covid. We urge everyone to join the effort by downloading the app and taking just a minute every day to log your health."
Long Covid is by no means a universal experience, and in fact many people who have contracted the coronavirus have had a mild illness or were asymptomatic.
The King's researchers found that while most people with Covid reported being back to normal in 11 days or less, around 1 in 7 (13.3%, 558 users) had symptoms lasting for at least four weeks, with around 1 in 20 (4.5%, 189 users) staying ill for eight weeks and 1 in 50 (2.3%, 95 users) suffering for longer than 12 weeks.
"These are conservative estimates, which, because of the strict definitions used, may underestimate the extent of Long-Covid," the researchers cautioned.
The U.K.'s National Health Service announced earlier in October that it will provide specialist help at clinics to those suffering from long-term symptoms of the coronavirus.