Introduction: In-hospital CAP mortality remains high in the first days of hospitalization and few studies have tried to identify different risk profiles for early mortality.

Aim: Determine the risk factors associated with CAP in-hospital deaths that occurred in the 1st day and up to the 3rd day of hospitalization.

Methods: A retrospective analysis of CAP hospitalizations deaths that occurred in National Health Service, in Portugal Mainland, between 2010 and 2018 was made based on two binary logistic regression models.

Results: Among 75845 in-hospital CAP deaths, most occurred on the 1st day (12.5%) followed by the 3rd day (9.4%). The risk factors associated with 1st day mortality were females [Adjusted OR (OR)=1.10 [1.05-1.16]], being from a county with higher unemployment rate (OR=1.01; [1.01-1.02]) or higher early leavers from education (ELE) rate (OR=1.02 [1.01-1.03]), admitted in a non-university hospital [level II and level I (OR=1.20/1.21]) and admission on Sunday (OR=1.10 [1.06-1.27]). Mortality in first 3 days showed an U-shaped effect for age [1-4 years (OR= 1.68 [1.51-1.87] and >95 years (OR= 1.84 [1.64-2.06)]; also living in a county with higher ELE rate (OR=1.01 [1.004-1.014), being admitted in Level I hospitals (OR=1.07 [1.04-1.10]), having cancer (OR=1.15 [1.10-1.19]), sepsis (OR=1.33 [1.10-1.59]) and submitted to mechanical ventilation (OR=1.558 [1.43-1.69]).

Conclusion: Early CAP in-hospital mortality was related to patient features (age, sex), disease severity (sepsis, mechanical ventilation), comorbidities and social vulnerability. Healthcare features (less differentiated hospitals and Sunday admission day) were also relevant.