Secondary Pneumonia Among Non-Communicable Disease Inpatients: A Retrospective Administrative Surveillance Study from a Chinese Tertiary Hospital.

BACKGROUND

Secondary pneumonia is an important inpatient complication, yet its burden among patients hospitalised for non-communicable diseases (NCDs) in China remains poorly characterised. We aimed to quantify this burden and its association with in-hospital mortality and prolonged length of stay (LOS).

METHODS

We conducted a retrospective observational study of 31,470 NCD inpatient records from a tertiary hospital in southwest China (2023 to 2025). Secondary pneumonia was identified by ICD-10 code J18 in any secondary diagnosis field. Three logistic regression models with patient-level clustered robust standard errors examined (1) factors associated with secondary pneumonia, (2) its association with in-hospital death, and (3) its association with LOS exceeding 10 days. A respiratory failure/ventilation coding proxy was included in Model 1 and excluded from Models 2 and 3 as a potential mediator.

RESULTS

Secondary pneumonia was identified in 2.94% of eligible admissions (n = 925), highest among admissions with neoplasms (6.15%). After adjustment, it was independently associated with in-hospital death (OR 3.15, 95% CI 1.75 to 5.67, p < 0.001) and LOS exceeding 10 days (OR 1.76, 95% CI 1.49 to 2.08, p < 0.001).

CONCLUSIONS

Secondary pneumonia was identified in 2.94% of NCD admissions and was independently associated with in-hospital death and prolonged LOS, with the highest coded prevalence among admissions with neoplasms. These findings support closer monitoring and evaluation of secondary pneumonia in NCD inpatients as a target for hospital quality improvement.