Risk factors for long COVID identified by scientists

Alexandra Thompson
·5-min read
Sad girl with headache. Young blonde woman feeling pain, touching her forehead, lying on sofa at home, copy space
Long COVID occurs when someone who has had the coronavirus continues to endure complications after testing negative for the infection. (Posed by a model, Getty Images)

Scientists have identified a range of factors that may raise a person’s risk of enduring long COVID.

It is increasingly coming to light that not everyone who overcomes the coronavirus returns to a clean bill of health, with some patients enduring everything from fatigue to organ damage after testing negative for the infection.

Perhaps most alarmingly, even people who had a relatively mild bout of the coronavirus can go on to endure lingering complications.

Read more: What is long COVID?

To better understand the long COVID phenomenon, scientists from King’s College London analysed data from their COVID symptom study app.

While anyone can develop long COVID, the team found certain factors raise an individual’s risk, including old age, obesity, being female and having asthma.

Watch: What is long COVID?

With the coronavirus only identified at the end of 2019, long COVID is fairly mysterious, with no set diagnosis.

In August, King’s scientists said up to half a million Britons may be experiencing symptoms after supposedly overcoming the infection.

The next month, the same team announced around 300,000 people have complications lasting more than four weeks, while 60,000 are still feeling the effects of the virus over three months later.

Read more: Long COVID may be four different syndromes

Medics have complained a lack of understanding over long COVID’s prevalence and cause makes treating patients tricky.

They may not be in the dark for long, however. NHS England and NHS Improvement have commissioned the National Institute for Health and Clinical Care Excellence (Nice) – a health watchdog – to develop a treatment guideline for long COVID, due by the end of 2020.

To help patients in the interim, the King’s scientists analysed data from the COVID app, where users input any symptoms and coronavirus test results.

Businesswoman with face mask working at her desk looking at computer monitor, in office. Female professional back to work after covid-19 pandemic lockdown.
Even mild coronavirus cases can develop into long COVID, highlighting the importance of face coverings, regardless of a person's age. (Posed by models, Getty Images)

Results – which have been seen by the BBC, but not officially published – suggest obese people are more at risk of long COVID.

Carrying an excessive amount of weight was flagged as a risk factor for coronavirus complications early in the outbreak.

Asthma was also identified as a long COVID risk factor. People with a severe form of the condition were told to shield during the height of the UK’s first wave.

The King’s study found lung disease raises a person’s long COVID risk, but no link was found for other medical conditions.

Read more: How many people have long COVID in the UK?

Perhaps surprisingly, the King’s scientists found females are more likely to develop long COVID than males. This is despite men being more at risk of ill health with the coronavirus infection itself.

“We’ve seen from the early data coming out that men were at much more risk of very severe disease and sadly of dying from COVID; it appears women are more at risk of long COVID,” study author Dr Claire Steves told the BBC.

Like coronavirus complications, long COVID was found to become more common with age, particularly in those over 50.

The King’s scientists also found having a range of coronavirus symptoms may raise a person’s risk of long COVID.

The NHS states the main signs of infection are a fever, cough, or loss of taste or smell.

This list has been accused of being too limited, with the World Health Organization (WHO) stating everything from diarrhoea to discolouration of the toes could indicate a positive case.

The US Centers for Disease Control and Prevention lists 11 potential signs of infection, ranging from shortness of breath to headaches.

“Having more than five different symptoms in the first week was one of the key risk factors [for long COVID],” said Dr Steves.

The study has also suggested long COVID’s prevalence.

The WHO states most coronavirus patients recover from severe symptoms within two to six weeks.

Patients enduring complications beyond this time are therefore generally considered to have long COVID, however, this definition has varied.

The King’s scientists found one in 20 former coronavirus patients endure complications for at least eight weeks.

One in seven is ill for at least four weeks and one in 45 for at least 12 weeks, the results suggest.

Watch: Can you catch coronavirus twice?

Off the back of their study, the King’s scientists created a piece of computer code to identify coronavirus patients who are at particular risk of long COVID.

The code is said to correctly identify those who may endure complications 69% of the time. In around a quarter of cases, however, it tells people who recover quickly they may develop long COVID.

Speaking of the research, health and social care secretary Matt Hancock said: “The findings of the COVID symptom study are stark and this should be a sharp reminder to the public, including to young people, that COVID-19 is indiscriminate, and can have long term and potentially devastating effects.”

The NHS recently announced a £10m ($13m) package to run designated long COVID clinics in every area of England.

One person who understands the frustration of long COVID all too well is Liz Walker.

The 57-year-old, from Wiltshire, told Yahoo UK she is “not the same person” she was before catching the coronavirus.

Scans and tests have revealed “issues with her blood, inflammation and heart and liver damage”.

With Walker enduring breathlessness, doctors have so far only prescribed an inhaler, which “didn’t help”.

The mother-of-four is due to have a heart scan in November to uncover the extent of the damage.