Newton, A. Kucharska

Abstract Rationale: SARS-CoV-2 infection may be associated with new or worsening respiratory symptoms that, if persistent, may contribute to “Long COVID.” Research is needed on the prevalence and risk determinants of Long COVID and related respiratory symptoms in adults with and without pre-existing obstructive lung disease or smoking history. Methods: C4R is a prospective, observational study that collected information on SARS-CoV-2 infection using standardized methods across 14 NIH-funded cohorts. The third wave of C4R questionnaires, administered June 2023 to January 2025, assessed self-reported Long COVID via the question, “Do you think that you are experiencing, or have ever experienced, what has been called “long COVID,” or symptoms related to COVID at least a month after your infection?” Questionnaires also assessed the presence (vs absence) of 22 symptoms that have been linked to Long COVID, including cough, shortness of breath, and post-exertional malaise. Pre-pandemic obstructive lung disease (COPD or asthma) and smoking status (ever/never) were harmonized from self-reported data collected at the most recent pre-pandemic cohort exam. Poisson regression was used to assess prevalence ratios (PRs) adjusting for age, sex, BMI, education, and pre-pandemic hypertension, diabetes, cardiovascular disease, and depressive symptoms. PRs for respiratory symptoms were tested according to self-reported Long COVID and history of non-hospitalized or hospitalized infection; effect modification by pre-pandemic lung disease and smoking was assessed by multiplicative interaction terms and in fully stratified models. Results: Among 23,434 questionnaire respondents, 1,484 (6.3%) self-reported Long COVID, including 246/1,262 (19.5%) with pre-pandemic lung disease and 664/4,018 (16.5%) with smoking history. The adjusted PR for Long COVID was 1.17 (95%CI:0.99-1.39;P=0.06) comparing participants with/without lung disease and 1.17 (95%CI:1.04-1.32;P=0.01) comparing participants with/without smoking history. Respiratory symptoms were more prevalent in those with self-reported Long COVID, as well as in those with a history of hospitalized or non-hospitalized infection (Table). Associations were generally stronger in participants without pre-pandemic lung disease (p-interaction<0.05 for all comparisons). Respiratory symptoms were also more prevalent with a history of repeated, and pre-Omicron infections, and were less prevalent among participants vaccinated prior to their first infection; findings were similar even after excluding participants with self-reported Long COVID. Conclusions: Long COVID is common, particularly in adults with pre-existing COPD or asthma or smoking history. Long COVID and history of SARS-CoV-2 infection, including non-hospitalized infections, was associated with greater respiratory symptom burden. Whether SARS-CoV-2 infection or Long COVID are associated with development or progression of obstructive lung diseases warrants future studies.