The impact of key secular trends during the first three waves the COVID-19 pandemic

IMPORTANCE: Patient age, comorbidity burden, and disease severity at presentation are the major factors associated with surviving COVID-19. Hospital-level factors including ICU occupancy may confer additional risk to individual patients, particularly at times of maximal stress on healthcare systems. The interaction of patient- and hospital-level factors over time during pandemic disease remains an area of active exploration. OBJECTIVE: To determine the impact of patient and hospital risk factors during episodic surges, characterize severity distribution between waves, and evaluate patient-level impact of ICU capacity on COVID-19 survivorship. DESIGN: Retrospective cohort study. SETTING: Four acute care hospitals within an integrated healthcare network in San Diego, California. PARTICIPANTS: All patients (18+ y.o.) admitted with a positive PCR test for SARS-CoV-2 or ICD-10 code for COVID-19 from March 1, 2020 through June 30, 2021. MAIN OUTCOME(S) AND MEASURE(S): Patient survivorship and length of stay. RESULTS: Six thousand eight hundred fifty-one patients were evaluated in this large cohort series. Patient level factors associated with mortality included: severity at admission (WHO Clinical Progression Score [WCPS]), age, gender, BMI, marital status, language preference, Elixhauser score, elevated laboratory (d-dimer, ferritin, LDH) or lower absolute lymphocyte count. When adjusting for patient age alone, survivorship during surges was also inversely associated with ICU occupancy, though this correlation was not present when adjusted for patient-level factors. CONCLUSIONS AND RELEVANCE: Patient age, comorbidity burden, and severity at the time of presentation are the major factors associated with surviving COVID-19. Hospital-level factors including ICU occupancy may confer additional risk to individual patients, particularly at times of maximal stress on healthcare systems.