Study estimates 18 million Americans have long-COVID

In a recent study posted to the medRxiv* preprint server, researchers evaluated the prevalence, risk factors, and impact of post-coronavirus disease (COVID) conditions (PCC) or long COVID on daily activities among adults residing in the United States (US).

PCC or long COVID refers to a diagnosis of novel, recurring or ongoing clinical findings or symptoms ≥4 weeks post-COVID 2019 (COVID-19). In the US, PCC prevalence assessments have been performed based on non-population-based sources such as EHRs (electronic health records), cohort studies, and cross-sectional studies with convenience sampling. Further, data on PCC's risk factors and effect on day-to-day activities are limited.

Study: The epidemiology of long COVID in US adults two years after the start of the US SARS-CoV-2 pandemic. Image Credit: Dmitry Demidovich / Shutterstock

About the study

In the present population-based cross-sectional study, researchers assessed PCC risk factors and prevalence and PCC impact on routine activities among US adult individuals.

A population-based survey was conducted in Spanish and English between 30 June and 2 July 2022 for 3,042 US adults. PCC prevalence was estimated by sociodemographic variables, with data adjustments for age and sex, based on questions developed by the United Kingdom's ONS (office of national statistics). Potentially eligible individual samples were drawn from 60,126,257 and 105,469,157 landlines and mobile numbers, respectively. Furthermore, online opt-in panel samples were drawn from across the country.

The status of current and previous COVID-19 was assessed. The prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure up to July 2022 was estimated as either meeting current COVID-19 case definitions or providing affirmative responses for acquiring COVID-19 before 15 July 2022. Participants self-reported if they experienced PCC symptoms such as concentration difficulties, breathlessness, and fatigue.

Respondents with ongoing COVID-19 were selected based on their self-reported responses of ≥1 positive COVID-19 test report based on healthcare provider-based diagnosis, rapid SARS-CoV-2 testing at home, or presence of COVID-19 symptoms with known close contact with SARS-CoV-2-positive individuals. In addition, respondents with prior COVID-19 history (before 15 June 2022) were identified based on self-reported responses of positive COVID-19 test report based on healthcare provider-based diagnosis, the most recently acquired SARS-CoV-2 infection, and rapid SARS-CoV-2 testing at home.

PCC impact on routine activities was assessed based on participant responses as "not at all; "yes, a little; or yes, a lot." Respondents were asked about comorbidities such as diabetes, cancer, obesity, pulmonary diseases such as chronic obstructive pulmonary disease (COPD), hepatic disorders, cardiovascular disorders, hypertension, organ transplantation, and immunosuppressive conditions.

Data were also obtained on the vaccination status of the participants. Log binomial modeling was used to analyze, and standardized prevalence and sex- and age-adjusted prevalence ratios (aPRs) were estimated. In addition, a sensitivity analysis was performed based on backward selection modeling for sex, age, ethnicity, comorbidities, the status of vaccination, and insurance.

Results

In the final sample, 62%, 32%, and 6.0% of survey respondents were enrolled from landlines, mobiles, and the online opt-in panel, respectively, with a 7.2% overall response rate across modalities. Among individuals with PCC, 44%, 27%, and 29% reported that they acquired SARS-CoV-2 infections most recently within the previous six months, six months to one year, and more than a year ago.

In total, 222 respondents (out of 3,042, 7.3%) reported PCC, 25% of whom said that their daily activities were impacted 'a lot' and 29% had acquired COVID-19 before more than a year. Participants who reported considerable impact of PCC on their daily living were aged >50 years (34%), were non-Hispanic Whites (34%), and were either jobless (36%) or earned below 60K (vs.>60K, 33%, aPR: 2.2).

The standardized PCC prevalence was greatest among respondents aged 25 to 34 years (10%), 35 to 44 years (9.0%), women (9.4%), non-Hispanic Whites (8.7%), with comorbidities (10%), jobs (8.9%), providing income ranging between $20,001 and 60,000 (8.8%) or between $60,001 and $100,000 (8.5%).

Sex- and age-adjusted modeling showed that PCC was more prevalent among female respondents (aPR: 1.8), with comorbidities (aPR: 1.6) who had jobs (vs. jobless, aPR: 1.3), and insurance (vs. unknown or no insurance, aPR: 1.9), and who had not received (vs. had received booster vaccinations, aPR: 1.7) or were unvaccinated (vs. administered booster doses, aPR: 1.4). In the sensitivity analysis, the effect magnitudes either remained unaltered or were strengthened.

The prevalence of having SARS-CoV-2-exposure as of July 2022 was 53%. The sex- and age-standardized prevalence of having SARS-CoV-2 exposure was greatest among those aged 25 years to 34 years (66%) and reduced with age. In addition, the standardized prevalence of ever having SARS-CoV-2-exposure was greater among Hispanic (61%) males (57%) with comorbidities (60%).

Overall, the study findings highlighted the enormous PCC burden and considerable variability in SARS-CoV-2 prevalence. Population-representative surveys are essential for PCC surveillance as an adjunct to ongoing PCC monitoring.

Using a population-representative sample of adults living in the US, we estimate that approximately 18.5 million adults, 7.3% (95% CI: 6.1-8.5%) of the US adult population, was experiencing long COVID (symptoms persisting for more than four weeks after the most recent SARS-CoV-2 infection that were not explained by something else) during the 2-week study period in June-July 2022.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Written by

Pooja Toshniwal Paharia

Dr. based clinical-radiological diagnosis and management of oral lesions and conditions and associated maxillofacial disorders.