Modifiable and nonmodifiable risk factors for non-ventilator-associated hospital-acquired pneumonia identified in a retrospective cohort study

Abstract

Objectives: Hospital-acquired pneumonia in nonventilated patients (nvHAP) belongs to the most common healthcare-associated infections. This study aimed to investigate risk factors for nvHAP in patients outside the intensive care unit, focusing on modifiable risk factors.

Methods: All inpatients admitted to an academic teaching hospital in Switzerland between 2017 and 2018 were included. nvHAP was defined according to European Centre for Disease Prevention and Control criteria. Patient days during and after ICU stay were excluded. Candidate risk factors-both constant and time varying-were included in uni- and multivariable Cox proportional hazards models. The decay ratio and the characteristic time of influence of hazard ratios (HRs) was estimated by adopting a linear decay in the Cox model.

Results: A total of 66 001 hospitalizations with 314 (0.48%) nvHAP and 471 401 patient days were included. Median age was 57 years (interquartile range: 38 to 71 years) and 32 253 (48.9%) patients were male. Among nonmodifiable risk factors, age (adjusted HR (aHR) 2.66 for age ≥60 years, 95% CI 1.59 to 4.45) and male sex (aHR 1.71, 95% CI 1.34 to 2.18) were independently associated with nvHAP. Time-varying exposures showing strongest independent association with nvHAP were tube feeding (aHR 3.24, 95% CI 2.17 to 4.83), impaired consciousness (aHR 2.32, 95% CI 1.63 to 3.31), and severely impaired activity and mobility (aHR 2.06, 95% CI 1.50 to 2.84). The association with nvHAP decayed within 7.1 to 13.2 days after these exposures ended.

Discussion: The risk for nvHAP varies with time, depending on the patient's medical condition and medical interventions. Several risk factors for nvHAP represent potential targets for specific prevention measures.

Keywords: Healthcare-associated infections; Hospital-acquired pneumonia; Infection prevention; Pneumonia; Risk factors.