Background Forced expiratory volume in 1 second (FEV 1 )/forced vital capacity (FVC) naturally decreases with age; however, an excessive decline may be related with increased morbidity and mortality. This study aimed to evaluate the FEV 1 /FVC decline rate in the Korean general population and to identify whether rapid FEV 1 /FVC decline is a risk factor for obstructive lung disease (OLD) and all-cause and respiratory mortality. Methods We evaluated individuals aged 40−69 years who underwent baseline and biannual follow-up spirometric assessments for up to 18 years, excluding those with airflow limitations at baseline. Based on the quartiles of the annual FEV 1 /FVC decline rate, the most negative FEV 1 /FVC change (1 st quartile of annual FEV 1 /FVC decline rate) was classified as rapid FEV 1 /FVC decline. We investigated the risk of progression to OLD and all-cause and respiratory mortality in individuals with rapid FEV 1 /FVC decline. Results The annual FEV 1 /FVC decline rate in the eligible 7,768 patients was 0.32 percentage point/year. The incidence rate of OLD was significantly higher in patients with rapid FEV 1 /FVC decline than in those with non-rapid FEV 1 /FVC decline (adjusted incidence rate, 2.119; 95% confidence interval [CI], 1.932–2.324). Rapid FEV 1 /FVC decline was an independent risk factor for all-cause mortality (adjusted hazard [HR], 1.374; 95% CI, 1.105–1.709) and respiratory mortality (adjusted HR, 1.353; 95% CI, 1.089–1.680). Conclusion The annual FEV 1 /FVC decline rate was 0.32%p in the general population in Korea. The incidence rate of OLD and the hazards of all-cause and respiratory mortality were increased in rapid FEV 1 /FVC decliners.

Background Limited data are available in COVID-19 patients on the prediction of treatment response to systemic corticosteroid therapy based on systemic inflammatory markers. There is a concern whether the response to systemic corticosteroid is different according to white blood cell (WBC) counts in COVID-19 patients. We aimed to assess whether WBC count is related with the clinical outcomes after treatment with systemic corticosteroids in severe COVID-19. Methods We conducted a retrospective cohort study and analysed the patients hospitalised for severe COVID-19 and received systemic corticosteroids between July 2020 and June 2021. The primary endpoint was to compare the composite poor outcome of mechanical ventilation, extracorporeal membrane oxygenation, and mortality among the patients with different WBC counts. Results Of the 585 COVID-19 patients who required oxygen supplementation and systemic corticosteroids, 145 (24.8%) belonged to the leukopoenia group, 375 (64.1%) belonged to the normal WBC group, and 65 (11.1%) belonged to the leukocytosis group. In Kaplan-Meier curve, the composite poor outcome was significantly reduced in leukopoenia group compared to leukocytosis group (log-rank p -value < 0.001). In the multivariable Cox regression analysis, leukopoenia group was significantly associated with a lower risk of the composite poor outcome compared to normal WBC group (adjusted hazard ratio [aHR] = 0.32, 95% CI 0.14–0.76, p -value = 0.009) and leukocytosis group (aHR = 0.30, 95% CI = 0.12–0.78, p -value = 0.013). There was no significant difference in aHR for composite poor outcome between leukocytosis and normal WBC group. Conclusion Leukopoenia may be related with a better response to systemic corticosteroid therapy in COVID-19 patients requiring oxygen supplementation. KEY MESSAGES In severe COVID-19 treated with systemic corticosteroids, patients with leukopoenia showed a lower hazard for composite poor outcome compared to patients with normal white blood cell counts or leukocytosis. Leukopoenia may be a potential biomarker for better response to systemic corticosteroid therapy in COVID-19 pneumonia.

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