The predisposing factors to having a coded diagnosis of Long COVID

Long COVID is characterized by a constellation of persistent symptoms following an initial infection with COVID-19 virus. The primary focus of this study was to investigate how the characteristics of people diagnosed with Long COVID differed from those of matched individuals who did not have a diagnosis of Long COVID, after at least one confirmed positive COVID-19 test.

A retrospective observational cohort study was performed using data collected for the time period, January 1, 2020 to January 31, 2024 from a population database of 2.85 million people.

The primary outcome was a primary care coded diagnosis, or referral for treatment of Long COVID following an acute COVID-19 infection, to a Long COVID clinic. Twenty six thousand, six hundred and twenty six (26,626) individuals were identified with a diagnosis of Long COVID and at least one previous recorded COVID-19 positive test. These were matched by age and sex with 133,165 individuals (i.e. an approximate ratio of 5 controls to one case) with at least one previous recorded COVID-19 positive test but no recorded diagnosis of Long COVID. Mortality rate was also analysed in relation to having a previous confirmed acute COVID-19 infection.

There was a higher proportion of people with 2, 3, 4 and 5 or more comorbidities in the diagnosed Long COVID group compared to those with one or no comorbidity. Black/ Black British ethnicity (+28 %) and Mixed ethnicity (+37 %) were both associated with a higher likelihood of a Long COVID diagnosis when compared to White ethnicity. Those in the most disadvantaged quintile (as measured by Townsend index) were more than twice as likely to have Long COVID than the most advantaged quintile. The risk of Long COVID increased by 5.7 % per each comorbidity, with modulation by the number of COVID-19 vaccinations. The risk of Long COVID doubled for every additional confirmed positive COVID-19 test. BMI did not have an effect when account was taken of Townsend quintile. Lastly, we analysed mortality rates following a COVID-19 infection. Female sex was associated with a lower risk of death. More disadvantaged individuals as measured by Townsend quintile were more likely to have died. This risk was nearly doubled for the most deprived quintile compared to least deprived quintile.

In this city region wide study with individuals matched for age and sex, we have determined that being in a socially disadvantaged situation and being Black/Black British or of Mixed ethnicity increased the risk of developing Long COVID. BMI did not have an effect when account was taken of Townsend quintile. These findings can inform public health messages and public health interventions going forward, whether in relation to Long COVID or future pandemic preparedness.