Fig. 3
Survival analysis with the cause-specific hazard model and step function (time-dependent Cox regression) to investigate the association of corticosteroids and ICU mortality over time. The estimated survival curves showed the estimated effect of exposure of corticosteroids on ICU mortality over time. Survival curves cross each other implying time-dependency of corticosteroid exposure; hence step function approach was used to handle non-proportional hazards assumption by stratification of time on day 17 of follow-up when hazards changed the direction statistically significant. Then, the proportional hazards assumption was met for both periods. Models were adjusted for gender, age, body mass index, hospital GAP, ICU GAP, diagnosis GAP, shock, ACE inhibitors, ARBs, Comorbidity, asthma, COPD, chronic kidney disease, haematological disease, diabetes mellitus, neuromuscular disease, autoimmune disease, ischaemic heart disease, hypertension, immunosuppression, dyslipidaemia, hypothyroidism, APACHE II, SOFA, pulmonary infiltrates, lactate dehydrogenase, white blood cells count, creatinine, urea, C-reactive protein, procalcitonin, Lactate, d-dimer, antibiotics, oseltamivir, lopinavir plus ritonavir, remdesivir, interferon, hydroxychloroquine, Tocilizumab, bacterial co-infection, ARDS severity, fractional of inspired oxygen (FiO2), positive end-expiratory pressure, tidal volume, partial pressure of carbon dioxide, pH, RIFLE criteria, myocardial dysfunction and corticosteroid treatment (short and long-term). ICU intensive care unit, ACE angiotensin-converting enzyme, ARBs angiotensin receptor blockers, COPD chronic obstructive pulmonary disease, APACHE Acute physiology and chronic health evaluation, SOFA sequential organ failure assessment, ARDS acute respiratory distress syndrome