Risk and Protective Factors for Long COVID Incidence in the Borriana COVID-19 Cohort from 2020 to 2023: A Prospective Population-Based Cohort Study

Background and Objective: After SARS-CoV-2 infection, Long COVID (LC) syndrome has occurred in a high proportion of patients, affecting their health. The aim of this study was to estimate the incidence of LC, as well as its risk and protective factors. Materials and Methods: We conducted a prospective population-based cohort study of the Borriana COVID-19 cohort (Castellon Province, Valencia Community, Spain) from May 2020 to August 2023, with a follow-up of 40 months, using the LC definition given by the World Health Organization. Inverse probability-weighted regression adjustment was applied in the statistical analysis. Results: With a participation rate of 63.8% and a total of 722 participants, the mean age was 37.7 ± 17.4 years, and 460 (62.3%) were female. Among them, 644 had experienced a SARS-CoV-2 infection, and 184 developed LC, corresponding to a cumulative incidence of 28.6%. At the time of follow-up, 135 patients remained affected by LC, and one LC-related death was recorded. Significant risk factors for LC included older age, female sex, being part of a small family, having a chronic disease, SARS-CoV-2 exposure, and disease severity. Asymptomatic COVID-19 infection and SARS-CoV-2 vaccination were significantly protective factors. Conclusions: A substantial incidence of LC was observed, along with a low recovery rate. Several risk and protective factors were identified. Continued follow-up of this cohort, improved medical care for patients with non-recovered LC, ongoing surveillance of SARS-CoV-2 infections, and vaccination of the at-risk populations against SARS-CoV-2 are recommended.