Long COVID affects 7% of those with virus

New analysis by Imperial College London has found that tens of thousands of people in England have lasting symptoms from COVID-19…more than a year after infection. The findings - which come from a representative sample of more than a quarter of a million people - suggest that 7% of those who have caught the virus have had symptoms lasting 12 weeks or more, which is classified as Long COVID. Dr Christina Atchison is from Imperial College’s School of Public Health and the first author on the study.

Christina - During the pandemic, we ran a study called the React Program, which some of your listeners may have heard of or indeed taken part in. And now we're following up with this study over a quarter of a million of those people and asking them about their current health. The main point of the study was to try and identify people that were suffering from persistent symptoms following infection with COVID and seeing how long those symptoms persisted for.

Chris - This comes under the umbrella of what is broadly dubbed long COVID.

Christina - Exactly. As far as the NHS and the WHO definition of long COVID goes, it is persistent symptoms following infection for 12 weeks or more, and that's the definition we used in the study.

Chris - Lots of people around the world have done this and we've arrived at an incidence of what we think it is in a population like the UK. So what does your study add?

Christina - A lot of previous studies have either been focused on patients who were hospitalised with COVID or focused on people just with long COVID, so haven't asked these sort of wider questions about symptoms in the general population. So we actually had two comparison groups. So people who never had COVID and also those people who got better very quickly after their infection. So after one or two weeks, which was most people. The other thing we did was we initially asked about current symptoms and health at the time in the survey, irrespective of whether people thought they had long COVID or not. And it was only later in the study that we asked them about their history of COVID and whether they thought they'd had long COVID. So we're hoping it provides much more unbiased data with respect to long COVID.

Chris - Indeed, because of course there could be social factors and everything else which was going on with a population going through a pandemic. Unsurprisingly, people are going to feel depressed, they are going to feel fatigued. They are going to feel run down in the aftermath whether or not they got COVID to some extent. And I suppose by having this big group of people, some of whom got infected, some of whom didn't, but they've all been through the same experience, you've got a really good comparison as to what really may be attributed to prior COVID infection, and what was the situation at the time.

Christina - Exactly. We found that the most common symptoms in people with long COVID were mild fatigue, difficulty thinking, concentrating - a lot of people use the term brain fog - and joint pains and shortness of breath. Now a lot of these symptoms are also fairly common in the general population, but we were able to show that they were far more common in people who had persistent symptoms following long COVID. Indeed, about 30% of people with long COVID said that their symptoms reduced substantially their ability to perform just sort of normal day-to-day activities. That percentage, 10%, was a lot less in the general population of people that either reported never having had COVID or just an acute illness. So showing really a substantial health burden in those people.

Chris - So what fraction of people got what we accept to be long COVID and what fraction of people got better and by when? So what do we think that the size of the iceberg, as it were, is now attributable to to COVID with these legacy symptoms that are going on indefinitely for some?

Christina - Overall people with COVID, with symptoms, about one in 13 developed symptoms that persisted for 12 weeks or more. So that's about 7.5%. and 1 in 20, so 5%, have persistent symptoms for more than a year. So I guess the important thing to say is most people with COVID get better and get better quickly within a couple of weeks, but about 1 in 13 do have these persistent symptoms beyond 12 weeks and 1 in 20 for more than a year.

Chris - And because you knew a lot about the people who were then going on to get these symptoms, can you flip things around and ask what the risk factors were displayed by those people that then ended up with them having those longer term or worse prognoses?

Christina - Yes, and they're very much in keeping with people that were also more at risk of catching COVID in the first place. Women were more likely to suffer from long COVID. That's quite consistent with other post viral syndromes and autoimmune conditions which are more common in women. We also found people that had severe acute infections, people that were hospitalised or were sort of really sort of bed bound with their symptoms, they again were more likely to develop persistent symptoms alongside people in clinical risk groups. So people with underlying health conditions like diabetes, respiratory problems. And importantly we found that the proportion of people with persistent symptoms fell substantially with more recent variants. So people with omicron were 88% less likely to have developed long COVID after the infection than people that were infected previously with the original Wuhan strain.

Chris - Where does this leave us then? Are we any closer to agreeing on what long COVID is and what about the implications going forward? Now we've got this understanding of who is likely to be at risk and how long for, where does this leave us?

Christina - There are still some inconsistencies in the definition. What we know is that this is real and it's a significant health burden for a not small percentage of the population. But what we just don't know yet is about the biology and what makes some people more susceptible or not.

Chris - Do you think it is unique to SARS-CoV-2, the cause of COVID, or do you think that because we had so many people succumbing to this all at the same time, that enough people raised a hand and said there's something wrong that we notice this, but were we to go and look at other infections that are seasonal or present in the same sort of way and can be as severe in some cases like the flu? Do you think we'd see a post viral syndrome attached to that too? And indeed, should we go looking?

Christina - My opinion is, this is probably seen with other infections. I mean as well as the research, I'm also a clinician and have seen people with coughs and colds and bad flus. And especially with the sort of loss of sense of taste and smell is something I've seen with other patients and have been symptoms they've had for a long time. I just think with COVID there was the whole entire world, the research community, focused on this one virus, understandably because of the impact it was having. But I would imagine if we went looking, we would also find these symptoms with other viruses. There are some similarities to something called chronic fatigue syndrome and post viral syndromes that have been reported after acute illnesses with other viruses. There is perhaps now justification to go and look at other viruses in a similar way that we've done with COVID.