Post COVID-19 condition diagnosis: A population-based cohort study of occurrence, associated factors, and healthcare use by severity of acute infection

Abstract Background The occurrence and healthcare use trajectory of post COVID-19 is poorly understood. Our aim was to investigate these aspects in SARS-CoV-2 positive individuals with and without a post COVID-19 condition diagnosis. Methods We conducted a population-based cohort study of adults in the entire Stockholm Region, Sweden, with a positive SARS-CoV-2 test from 1 March 2020 to 31 July 2021, stratified by severity of the acute infection. The study outcome was a post COVID-19 condition diagnosis registered any time 90 to 360 days after positive test. We performed Cox regression models to assess baseline characteristics associated with post COVID-19. Individuals with post COVID-19 were then propensity-score matched to individuals without post COVID-19 to assess healthcare use beyond the acute infection. Findings: Among 204 805 SARS-CoV-2-positive individuals, the proportion receiving a post COVID-19 diagnosis was 1% among individuals not hospitalized for their COVID-19 infection, 6% among hospitalized, and 32% among ICU-treated individuals. Female sex was associated with post COVID-19 among non-hospitalized and hospitalized individuals, with interactions between age and sex. Previous mental health disorders and asthma were associated with post COVID-19 among non-hospitalized [aHR 2·18 (95% CI 1·98 − 2·39), aHR 2·09 (95% CI 1·82 − 2·40)] and hospitalized [aHR 1·38 (95% CI 1·17 − 1·64), aHR 1·64 (95% CI 1·34 − 2·00)] individuals. Among individuals with post COVID-19, the monthly proportion with outpatient care visits after the infection compared to before the infection was substantially elevated up to one year after the acute infection, with substantial proportions of this care attributed to care related to post COVID-19. Interpretation: The differential association of age, sex, comorbidities, and healthcare use with severity of the acute infection indicates different trajectories and phenotypes of post COVID-19 condition, with incomplete resolution one year after infection.