Post-COVID-19 syndrome (PCS) is characterised by persistent symptoms, such as fatigue, dyspnoea, depression and sleep problems, following SARS-CoV-2 infection. The long-term course and impact on quality of life remain unclear. This review aims to synthesise evidence on longitudinal changes in symptom prevalence, severity and health-related quality of life (HRQoL) in adults with PCS.

This systematic review will include longitudinal studies (randomised controlled trials, non-randomised trials, prospective and retrospective cohort studies) of adults (≥18 years) with PCS, defined by symptoms persisting beyond 4 weeks after acute infection. Eligible studies must report changes in prevalence or severity of fatigue, dyspnoea, depression, sleep problems or HRQoL from baseline to at least one follow-up visit.

We will systematically search MEDLINE, Embase, PsycINFO, Web of Science, Scopus, CINAHL and Epistemonikos, with no restrictions on language, date or publication status. Two reviewers will independently screen studies, extract data and assess risk of bias using validated tools appropriate to study design. Disagreements will be resolved by consensus or a third reviewer.

A narrative synthesis will summarise study characteristics and symptom trajectories. Where sufficient data are available, random-effects meta-analyses will be conducted to estimate pooled changes in symptom prevalence (ORs), severity ((standardised) mean differences) and HRQoL ((standardised) mean differences). Meta-regression and subgroup analyses will explore potential effect modifiers. Certainty of evidence will be evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

No ethical approval is required. Findings will be disseminated via peer-reviewed publication, conference presentations and plain language summaries.

CRD420251011612.