About 2 million people in the UK currently have long-term COVID, according to the latest figures from the Office for National Statistics.
In the United Kingdom, long-term COVID is defined as “signs and symptoms that persist or develop after acute COVID-19”. This definition is further divided into people who have symptoms between four to 12 weeks after infection (continuing symptomatic COVID-19) and for 12 weeks or more (post-COVID syndrome).
Symptoms can include fatigue, shortness of breath, difficulty concentrating, and more, but the exact nature of the symptoms is not well understood. There are also gaps in our knowledge when it comes to the frequency of prolonged COVID and whether there are specific factors that expose people to a higher risk of developing the condition.
All of this is due in part to the fact that the symptoms used to define long-term COVID often vary between studies, and these studies are usually based on relatively few people. So the results may not apply to the wider population.
In a new study published in the journal Nature Communications, my colleagues and I looked at data from ten long-term studies based in the United Kingdom, along with 1.1 million anonymous electronic health records from English common practices. Based on these data, we investigated whether the severity of long-term COVID (how common it is) differs in demographic and health characteristics, such as age, gender, and pre-existing medical conditions.
The studies were created before the pandemic and followed the participants for many years. From these studies, we used data from 6,907 people who reported having COVID-19. Comparing this with data from the electronic health records of people diagnosed with COVID allowed us to study the incidence of prolonged COVID in those who saw their GP for it and those who did not.
Read more: Long COVID: a public health expert’s campaign to understand the disease
We found that of those who self-reported having COVID in the studies, the proportion who reported symptoms for more than 12 weeks ranged from 7.8% to 17%, while 1.2% to 4.8% reported “Exhausting” symptoms.
In the electronic health records, we found that only 0.4% of people diagnosed with COVID were subsequently recorded as long-term COVIDs. This low proportion of diagnoses by general practitioners may be due in part to the fact that official registration of long-term COVID was introduced for physicians only in November 2020.
National baseline study on COVID-19 provided by the author
The proportion of people who report symptoms for more than 12 weeks varies with age. There were also many variations depending on which definition each study used to capture prolonged COVID. But overall, we found evidence to suggest that an increased risk of prolonged COVID is associated with an increase in age to 70 years of age.
The studies included participants of different ages, from an average age of 20 to 63 years. Using a strict definition of symptoms affecting daily function, we found that the proportion of people with symptoms for 12 weeks or more usually increased with increasing age, ranging from 1.2% for 20-year-olds to 4.8% for those with 63 years.
We also found that a number of other factors were associated with an increased risk of developing prolonged COVID. For example, as a woman, poorer pre-pandemic mental health and overall health, obesity and asthma have also been identified as risk factors in both long-term studies and e-health records.
These findings are largely consistent with other emerging evidence of sustained COVID. For example, a recent international review found that women were 22% more likely than men to experience prolonged COVID.
Read more: COVID: long-lasting symptoms, less common in children than in adults – new study
It will be important to understand why these links exist, which is beyond the scope of our study. But identifying who may be at higher risk of long-term COVID is important, and as we continue to learn more, it can provide information on public health prevention and treatment strategies.
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