Causes of death for patients with community-acquired pneumonia: results from the Pneumonia Patient Outcomes Research Team cohort study.

BACKGROUND: To our knowledge, no previous study has systematically examined pneumonia-related and pneumonia-unrelated mortality. This study was performed to identify the cause(s) of death and to compare the timing and risk factors associated with pneumonia-related and pneumonia-unrelated mortality.
METHODS: For all deaths within 90 days of presentation, a synopsis of all events preceding death was independently reviewed by 2 members of a 5-member review panel (C.M.C., D.E.S., T.J.M., W.N.K., and M.J.F.). The underlying and immediate causes of death and whether pneumonia had a major, a minor, or no apparent role in the death were determined using consensus. Death was defined as pneumonia related if pneumonia was the underlying or immediate cause of death or played a major role in the cause of death. Competing-risk Cox proportional hazards regression models were used to identify baseline characteristics associated with mortality.
RESULTS: Patients (944 outpatients and 1343 inpatients) with clinical and radiographic evidence of pneumonia were enrolled, and 208 (9%) died by 90 days. The most frequent immediate causes of death were respiratory failure (38%), cardiac conditions (13%), and infectious conditions (11%); the most frequent underlying causes of death were neurological conditions (29%), malignancies (24%), and cardiac conditions (14%). Mortality was pneumonia related in 110 (53%) of the 208 deaths. Pneumonia-related deaths were 7.7 times more likely to occur within 30 days of presentation compared with pneumonia-unrelated deaths. Factors independently associated with pneumonia-related mortality were hypothermia, altered mental status, elevated serum urea nitrogen level, chronic liver disease, leukopenia, and hypoxemia. Factors independently associated with pneumonia-unrelated mortality were dementia, immunosuppression, active cancer, systolic hypotension, male sex, and multilobar pulmonary infiltrates. Increasing age and evidence of aspiration were independent predictors of both types of mortality.
CONCLUSIONS: For patients with community-acquired pneumonia, only half of all deaths are attributable to their acute illness. Differences in the timing of death and risk factors for mortality suggest that future studies of community-acquired pneumonia should differentiate all-cause and pneumonia-related mortality.