Long COVID: What are the risk and protective factors?

A population-based, multicentre study finds female gender, transportation-, logistics- or discipline-related occupation, living with domestic workers, smoking, poor or very poor self-perceived health status, ≥3 chronic diseases, chronic medication use, and critical severity of COVID-19 to be associated with severe long COVID, while prior receipt of ≥2 doses of COVID-19 vaccines serves as a protective factor.

The WHO defines long COVID as a condition that usually occurs 3 months from COVID-19 onset, with symptoms that last ≥2 months and could not be attributed to an alternative diagnosis. “Our recent study showed that approximately 76 percent of COVID-19 patients suffered from long COVID symptoms, including fatigue, poor memory and hair loss, within 6 months of hospital admission. Although the pathogenesis, complications, and epidemiological and clinical characteristics of COVID-19 in the acute phase have been [extensively] evaluated, few studies have characterized the epidemiology, symptomatology, and risk factors of long COVID,” wrote the researchers from the Chinese University of Hong Kong. [Gut 2022;71:544-552; JAMA 2020;324:782-793; BMJ 2020;doi:10.1136/bmj.m3862]

To address knowledge gaps in risk and protective factors of long COVID, the team performed a survey of 2,712 community-dwelling COVID-19 patients from Beijing, Shanghai, Guangzhou, and Hong Kong in June 2022. The survey comprised 31 questions on sociodemographics, past medical history, long-term use of medication, history of COVID-19 vaccines received, and severity of COVID-19. The respondents were also asked about COVID-19 symptoms that persisted for ≥3 months after the infection. [JMIR Public Health Surveill 2023;doi:10.2196/42315]

Most respondents suffered from pneumonia at the time of COVID-19 diagnosis (78.9 percent), required hospital admission (71.7 percent) and oxygen supplementation (52.6 percent), and received antiviral agents (64.4 percent). Over half of the respondents (57.2 percent) had severe or critical COVID-19, while a significant proportion were given artificial ventilation (36.4 percent) and admitted to the ICU (34.7 percent). Most of the respondents had been vaccinated before COVID-19 diagnosis, with the majority having received ≥3 doses (56.2 percent) or two doses (29.0 percent) of the inactivated CZ02 vaccine, and a smaller proportion (6.2 percent) who had received ≥2 doses of the BNT162b2 mRNA vaccine.

According to multivariate regression analysis, female patients (adjusted odds ratio [aOR], 1.49; 95 percent confidence interval [CI], 1.13–1.95), patients engaged in transportation, logistics or the discipline workforce (aOR, 2.52; 95 percent CI, 1.58–4.03), patients living with domestic workers (aOR, 2.37; 95 percent CI, 1.39–4.03), smokers or ex-smokers (aOR, 1.55; 95 percent CI, 1.17–2.05), respondents with poor or very poor self-perceived health status (aOR, 15.40; 95 percent CI, 7.88–30.00), those with more chronic diseases (one chronic disease: aOR, 1.92; 95 percent CI, 1.24–2.97; two chronic diseases: aOR, 2.71; 95 percent CI, 1.21–6.05; ≥3 chronic diseases: aOR, 2.71; 95 percent CI, 1.54–4.79), long-term medication users (aOR, 4.38; 95 percent CI, 1.66–11.53), and patients with critical severity of COVID-19 (aOR, 1.52; 95 percent CI, 1.07–2.15) were at higher risk of developing severe long COVID.

In contrast with the multiple risk factors for long COVID, only one factor had a protective effect. Prior COVID-19 vaccination with ≥2 doses of CZ02 vaccine (aOR, 0.35; 95 percent CI, 0.14–0.90; p=0.03) or BNT162b2 vaccine (aOR, 0.22; 95 percent CI, 0.08–0.63; p=0.005) was associated with a lower risk of long COVID.