Introduction: The estimated prevalence of FRCs, identified by a NQ score ?23/64, is 8% in the general population (14% of women, 2% of men).

Aims: Assess the prevalence of FRCs after COVID-19 and identify associated factors.

Methods: Retrospective observational monocentric study. Patients performing pulmonary function test (PFT) in our centre in 2021 were invited to fill in a NQ and a Dypnoea-12 questionnaire (D-12; exploring physical and affective dimensions of dyspnoea). The study population was divided into FRCs+ group (NQ ?23) and no-FRCs group (NQ ?22). Demographics, data about the COVID-19 episode, and PFT, were also collected.

Results: 169 patients were included (100 men). Median time since COVID-19 was 6.1 [4?9.7] months. The prevalence of FRCs was 25% (n=42): 36% of women (n=25) and 17% of men (n=17) (p=0.004). Mean age was 57.8±14.3 years, mean BMI was 28.9±6 kg.m^-2, with no significant difference between both groups. Median NQ and total D-12 scores were 30 [27?37] and 19 [13?26] in the FRCs+ group, versus 8 [3?15] and 4 [0?10] in the no-FRCs group, respectively (p<0.0001). NQ was strongly correlated with D-12: r=0.71 for physical domain, r=0.69 for affective domain, r=0.73 for total score (all p<0.0001). Neither median time since COVID-19 nor PFT results were predictive for a NQ score ?23.

Conclusion: The prevalence of FRCs was much higher after COVID-19 than in the general population, with a preserved female predominance. The presence of FRCs was independent from other demographic characteristics, but strongly correlated with the physical and affective dimensions of dyspnoea, and inversely correlated with the initial severity of COVID-19.