EXPRESS: Risk Factors Associated with Chronic Pain and Fibromyalgia-Like Symptoms Post-COVID Hospitalization.

Post-COVID syndrome (PCS) may manifest as chronic pain and fibromyalgia-like symptoms, but the specific risk factors contributing to these outcomes remain poorly understood. We conducted a prospective cohort study using data from the ongoing "Post-Acute Sequelae of SARS-CoV-2 Infection (PASC)" study to identify predictors of chronic pain and fibromyalgia-related phenotypes among previously hospitalized COVID-19 patients. Participants were adults (n = 756, mean age 55, 47% female) hospitalized between March and August 2020 at the University of São Paulo Medical School. Clinical and demographic data from hospitalization, along with psychological, functional, and cognitive assessments at 3-11 months post-discharge (phase 1), were used to predict chronic pain, chronic widespread pain (CWP), fibromyalgia-like symptoms (FLS), and probable fibromyalgia (FM) at a 2-3 year follow-up (phase 2). Multivariate logistic regression analyses revealed that higher anxiety/depression severity (OR 1.35; 95% CI 1.09-1.69; p = 0.008) and reduced left handgrip strength (OR 0.95; 95% CI 0.92-0.98; p < 0.001) at phase 1 significantly predicted chronic pain at phase 2. For fibromyalgia-related phenotypes, greater left-side pain, insomnia severity, and weaker left handgrip strength were consistently associated with increased risk across all outcomes (CWP, FLS, FM), with statistically significant odds ratios ranging from 1.07 to 1.44. These findings highlight key modifiable risk factors-particularly psychological distress, sleep disruption, and muscle weakness-that may contribute to the development of chronic pain and fibromyalgia symptoms following COVID-19 hospitalization. Early identification and targeted intervention on these domains could improve long-term outcomes in PCS populations.