Study Reveals Data on Long COVID Frequency and Risk Factors

Woman lying down suffering from symptoms of long covid
Source: Westend61/Getty Images

A COVID-19 study led by Kings College London reports a frequency of ‘long COVID’ of up to 17% in the U.K. population as well as analyzing who is most at risk of experiencing extended symptoms after becoming infected with SARS-CoV-2.

The study, published in the journal Nature Communications, showed that being female, older age, obesity, asthma, and poor overall pre-pandemic physical and mental health were all risk factors for experiencing long COVID.

More than two years into the COVID-19 pandemic, data on long term effects of infection with the SARS-CoV-2 virus are becoming clearer with a significant number of people reporting long-term or recurrent symptoms of infection.

“The UK’s National Institute for Health Care and Excellence defines COVID-19 symptom duration with three categories: less than 4 weeks, 4–12 weeks, and more than 12 weeks, with the latter two categories both considered ‘long COVID’,” explain the researchers.

However, although long COVID has been widely talked out in the media, more precise information on how frequently it occurs and who is most at risk for developing these extended symptoms is less clear.

To investigate this further, Claire Steves, a senior lecturer at Kings College London, and colleagues collected survey data from 6907 people with self-reported COVID-19 from 10 U.K. longitudinal study samples and 1.1 million individuals with diagnostic codes indicating COVID-19 diagnosis in electronic healthcare records. All study data was collected up to spring 2021.

The team found that between 7.8% and 17% of individuals reported long COVID for more than 12 weeks, with 1.2–4.8% reporting debilitating symptoms.

Women were more likely to develop long COVID than men with relative increased risks of having symptoms for 4-12 and more than 12 weeks in the longitudinal cohort compared with men of 49% and 60%, respectively. There was also a U-shaped association with age with lower risk in those aged 18-24 and over 80 years and highest risk in those aged 45–54, and 55–69 years. In individuals between the age of 18 to 70 years, risk for long COVID increased by up to 3% per decade in both the longitudinal cohort and electronic health records groups.

White ethnicity, poor pre-pandemic physical and mental health, overweight or obesity, and presence of asthma were all also linked to increased risk for experiencing long COVID in both the longitudinal study and electronic health record data. But results for other possible risk factors such as those related to cardiovascular health were not conclusive.

The authors acknowledge that more information is needed, but hope these results will help guide future studies and also help identify at risk groups.

“Representative population-based studies will need to provide ongoing estimates across the spectrum of functional limitation to help plan appropriate provision of healthcare. Our data suggest that revisions of diagnostic criteria within primary care may be appropriate, particularly for demographic groups which are less in touch with healthcare services,” conclude the authors.

“Although causal inferences cannot be drawn from these data, our findings justify further investigations into the role of sex difference, age related change, and/or immunity and respiratory health in development of long COVID. Older working individuals, with high levels of comorbidity, may particularly require support.”

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