Background: The severity and prognosis of the COVID-19 pandemic are impacted by chronic illnesses that coexist with it.

Patients and methods: A cohort of 301 patients hospitalized to Sohag University Hospital between May 2020 and May 2023 who had a confirmed COVID-19 infection. There were two groups of patients: group 1 included cases with chronic respiratory diseases (CRD) and group 2 included cases without CRD. Both groups were compared as regard demographic data, comorbidities, laboratory and radiological findings, severity and outcome.

Results: Group 1 included 150 cases. The need for non- invasive ventilation (NIV) and mechanical ventilation was more in group 1 (p ≤ 0.001). Severe cases and mortality were more detected in group 1 (p ≤ 0.001). Following multiple logistic regression analyses, predictors of severity in cases with CRD included factors related to symptoms as headache and prolonged duration of symptoms (Odd ratio 1.166, CI 1.088 - 1.249) , factors related to laboratory investigations including high neutrophil count, lymphopenia, increase neutrophil lymphocyte ratio (NLR), high serum ferritin and LDH(Odd ratio 1.006, CI 1.004 - 1.008), increase PaCO2, increase HCO3 (Odd ratio 0.883, CI 0.793 - 0.982) and the need for O2 inhalation in management .

Conclusion: Coexistence of CRD and COVID 19 is accompanied by higher disease severity and mortality. Predictors of severity in CRD cases with COVID 19 include headache and prolonged duration of symptoms, high neutrophil count, lymphopenia, increase NLR, high serum ferritin and LDH, increase PaCO2, increase HCO3 and need for O2 inhalation in management.