Adults with prepandemic respiratory conditions, including asthma, bronchitis, and recurrent upper respiratory infections, are significantly more likely to develop long COVID after a mild-to-moderate COVID-19 infection, according to a large population-based case-control study published yesterday in BMC Infectious Diseases.
The findings come as new data suggest that long-COVID prevalence in the United States may be gradually declining and recovery becoming more common, though millions remain affected.
Even mild infections can lead to long COVID
Using health care registry data from the Stockholm region, researchers from the Karolinska Institutet in Sweden identified 5,589 adults diagnosed as having long COVID in 2021 and matched them to 47,561 controls. Nearly 70% of long-COVID patients were women.
When the researchers looked at participants’ prepandemic respiratory diagnoses, they found that those later diagnosed with long COVID had significantly higher odds of having had a documented respiratory disease in 2019, prior to SARS-CoV-2 circulation.
Acute upper respiratory tract infections were more common among those who went on to develop long COVID (odds ratio [OR], 2.47 in men; 2.22 in women), as were asthma (OR, 1.76 in men; 1.95 in women) and bronchitis (OR, 2.15 in men; 2.71 in women).
The study focused exclusively on non-hospitalized patients, underscoring how persistent symptoms can follow even mild infections.
Because the 2019 data were collected before any possible exposure to COVID, they provide the clearest indication of pre-existing risk. (Respiratory diagnoses recorded in 2020 may have overlapped with COVID infection or early post-infectious symptoms.)
“Our study shows that women and individuals with pre-pandemic respiratory conditions (year 2019), including asthma, had a higher risk of developing long COVID,” the authors conclude, adding that further research is needed to understand the underlying mechanisms that link pre-existing respiratory conditions to long COVID.
8% of US adults have had long COVID
At the population level, rates of long COVID appear to be declining, but the condition remains common. In a research letter published this week in JAMA Network Open, researchers led by a team at Yale New Haven Hospital analyzed national health data from 2022 to 2024 and estimated that 8.3% of US adults report having experienced long COVID.
Among the 8.3%, 60% reported recovery over time in 2024—compared with 51% in 2020—with the prevalence of long COVID declining during the study period. Still, certain groups remain disproportionately affected. Female sex, age 35 to 64 years, and lower household income were consistently associated with higher odds of long COVID.
Taken together, the findings suggest that while many patients gradually recover, a substantial minority experience prolonged symptoms, and those with underlying respiratory disease may face heightened risk.
The authors of the Swedish study conclude: “Understanding the link between common respiratory conditions managed in primary care, including asthma and bronchitis, and long COVID is vital for refining clinical strategies and improving outcomes in post-viral conditions.”
