Association of pre-pandemic respiratory system diseases with Long COVID: a population-based case-control study
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Objectives
Long COVID, defined as diverse symptoms persisting >3 months post-infection, remains a major post-pandemic healthcare burden. Here we investigate risk factor posed by pre-existing respiratory symptoms and illnesses for development of long COVID, with focus on individuals with mild-to-moderate COVID-19 at the primary infection, that did not require hospitalization during the primary SARS-CoV-2 infection.
Methods
This case-control study was designed to investigate the prevalence of respiratory system-related diagnoses in adult, non-hospitalized long COVID patients (cases) compared to matched controls without a history of long COVID. Data was extracted from the Stockholm Region’s database (VAL) and included diagnoses 12 months pre- and 6 months post-long COVID diagnosis as well as pre-pandemic diagnoses (year 2019). Adjusted logistic regression models were applied.
Results
Patients with Long COVID displayed higher frequencies of pre-pandemic respiratory conditions (year 2019) as well as 12 months before long COVID diagnosis compared to controls, including acute upper respiratory tract infections (men: Odds ratio (OR) 2.47, women: OR 2.22), asthma (men: OR 1.76, women: OR 1.95), and bronchitis (men: OR 2.15, women: OR 2.71). ORs for asthma were the highest 12 months before long COVID diagnosis (men: OR 4.18, women: OR 3.76).
Conclusion
Patients with Long COVID with a mild-to-moderate primary SARS-CoV-2 infection had higher prevalence of pre-existing respiratory conditions than controls, suggesting that respiratory diseases including asthma were a significant risk factor for long COVID also in the non-hospitalized population. Understanding the link between chronic respiratory illnesses and long COVID is vital for refining clinical strategies and improving outcomes in post-viral conditions.
Key take-home message
Pre-pandemic respiratory diagnoses, including asthma, as well as female sex represent significant risk factors for developing long COVID in individuals with a mild-to-moderate primary SARS-CoV-2 infection not requiring hositalization.
