Prevalence and risk factors for long COVID after mild disease: a longitudinal study with a symptomatic control group. (preprint)

ABSTRACT

Background There is limited data on the prevalence and risk factors for long COVID, with a shortage of prospective studies with appropriate control groups and adequate sample size. We therefore performed a prospective study to determine the prevalence and risk factors for long COVID. Methods We recruited patients age [≥] 15 years who were clinically suspected of having acute SARS-CoV-2 infection from September 2020 to April 2021. Nasopharyngeal swabs were collected for RT-PCR 3-5 days post symptom onset. Clinical and sociodemographic characteristics were collected using structured questionnaires from persons positive and negative for SARS-COV-2. Follow-up was performed by telephone interview to assess early outcomes and persistent symptoms. For COVID-19 cases, 5D-3L EuroQol questionnaire was used to assess the impact of symptoms on quality of life. Results We followed 814 participants (412 COVD-19 positive and 402 COVID-19 negative persons) of whom the majority (741 / 814) had mild symptoms. Both the COVID-19 positive and the COVID-19 negative groups had similar sociodemographic and clinical characteristics, except for the rate of hospitalization (15.8% vs 1.5%, respectively). One month after disease onset, 122 (29.6%) individuals reported residual symptoms in the COVID-19 positive group or the long COVID group versus 24 (6%) individuals in the COVID-19 negative group. In the long COVID group, fatigue, olfactory disorder, and myalgia were the most frequent symptoms which occurred in the acute phase. Compared to recovered patients, female sex, older age and having > 5 symptoms during the acute phase were risk factors for long COVID. Quality of life was evaluated in 102 out of 122 cases of long COVID with 57 (55.9%) reporting an impact in at least one dimension of the EuroQol 5D-3L questionnaire. Conclusion In this prospective study consisting predominantly of patients with mild disease, the persistence of symptoms after acute disease was highly associated with long COVID-19 (29.6% vs 6% of COVID negative group). The risk factors for long COVID were older age, female sex, and polysymptomatic acute disease.