Chronic Quality of Life Impairment in Long COVID: Insights from a Four-Year Longitudinal Cohort Using the PAC-19QoL

<ns7:p>Background Long COVID-19 has emerged as a chronic condition with substantial effects on quality of life. The PAC-19QoL instrument was developed to capture these impacts, but its ability to reflect and predict trajectories of long COVID-19 remains to be validated. Methods We conducted a longitudinal cohort study between December 2020 and March 2025 including 122 participants with confirmed long COVID-19. PAC-19QoL scores were collected at baseline and during repeated follow-up surveys. Generalized estimating equations (GEE) with different correlation structures were applied to examine associations between long COVID-19 duration, demographic and clinical factors, and PAC-19QoL scores. Predictions of mean and median PAC-19QoL scores were generated for up to five years. Results At baseline, participants had a mean age of 46.5 years and were predominantly female (91.2%). The mean duration of long COVID-19 was 9.6 months. PAC-19QoL scores fluctuated between 125 and 145 across the study period, with stable mean and median values. In the exchangeable GEE model, longer long COVID-19 exposure duration was associated with higher PAC-19QoL scores (β = 1.08, p &lt; 0.001). Male sex (β = –18.1, p &lt; 0.001), older age (β = –0.50 per year, p &lt; 0.001), and hospitalization (β = –23.5, p &lt; 0.001) were associated with lower scores, while BMI showed a modest positive effect (β = 0.39, p = 0.038). Time in study and the Exposure × Time interaction was not significant. Predictive modelling suggested that mean PAC-19QoL scores will remain stable over the next five years, with minimal decline from 137.6. Conclusions The PAC-19QoL instrument demonstrates sensitivity to long COVID-19 exposure duration and key demographic and clinical characteristics. However, trajectories of quality of life appear largely stable over extended periods, highlighting the chronic and persistent burden of long COVID-19. PAC-19QoL may serve as both a monitoring and predictive tool for long COVID-19.</ns7:p>