Among people with community-acquired pneumonia, those with aspiration pneumonia are likely to have worse outcomes than other patients, according to a review of previously published data.
The study, “Prognostic implications of aspiration pneumonia in patients with community acquired pneumonia: A systematic review with meta-analysis,” published in the journal Scientific Reports, suggested that aspiration pneumonia — caused by inhaling foods, liquids, saliva or vomit into the lungs — more often leads to death, and may also be linked to recurrent pneumonia episodes.
Since doctors seldom witness the aspiration of fluids that cause the pneumonia, the condition is defined as pneumonia in patients who are at risk for aspiration. Such patients often have reduced consciousness, swallowing difficulties, or obstructed airways.
This uncertainty makes studies of aspiration pneumonia difficult, and the research team suggested that uniform criteria to establish aspiration risk needs to be developed and accepted to allow studies of potential interventions that might decrease the risk of aspiration pneumonia.
In a collaboration between Virginia Commonwealth University School of Medicine and Nagasaki University School of Medicine in Japan, researchers evaluated previously published studies to assess how common the condition is, and how it relates to poor outcomes, such as death.
A total of 19 studies were included in the analysis, and the proportion of patients with aspiration pneumonia ranged from 1.5% to 50.4% across the studies. This large span was likely caused by differences in how patients were selected for a study, how “aspiration pneumonia” was defined, and by individual judgment differences between physicians in setting the diagnosis, the researchers noted.
Among seven studies (including 69,129 patients) that evaluated the risk of dying in a hospital (outside of the intensive care unit or ICU), researchers found a 3.6 times higher risk of death in those with aspiration pneumonia compared to patients with non-aspiration types.
Oddly, two of the five studies that analyzed death rates in the ICU came to the opposite conclusion, showing that patients with aspiration pneumonia had a lower risk of dying. The five studies, including a total of 1,644 patients, were all performed by the same research group.
Five other studies, including more than 6,000 patients, analyzed 30-day mortality. Again, aspiration pneumonia was linked to a higher risk of death in four of the five. A few studies also analyzed long-term outcomes, showing that aspiration pneumonia led to a higher risk of death both at 90 days and one year after the the start of the disease.
Aspiration risk was also linked to both readmissions, and to higher rates of recurrent pneumonia. One study, however, found that other risk factors, such as age or a lack of pneumococcal vaccination, but not aspiration risk, were linked to recurrent pneumonia.
“To summarize our results, aspiration risk is associated with in-hospital and 30 day mortality outside the ICU, with long term mortality, all cause readmission, and recurrent pneumonia. Most of the studies demonstrated that aspiration pneumonia is an independent risk factor for these outcomes,” the team concluded.
The researchers also emphasized: “Although we have provided specific ad hoc definitions for pneumonia and for aspiration risk; these are still somewhat subjective making case ascertainment challenging. If uniform criteria to establish aspiration risk can be developed and accepted for future studies, this will enable well controlled and appropriately powered studies to determine if interventions that can decrease aspiration risk, will also affect morbidity and mortality in this population.”