This study confirms that the cost of pneumonia after stroke is not trivial and that the average adjusted cost may be higher than previously estimated. Katzan, et al. estimated the cost of pneumonia to be $21,338 (95% CI $20,762–21,913), inflation-adjusted in 2009 US dollars, about $6,300 less than the estimate from this study.10
If this study were limited to Medicare recipients, as in Katzan’s study, the average adjusted incremental cost of pneumonia would be $23,292, within $2,000 of the inflation-adjusted cost estimated previously.
This study also confirms that pneumonia after stroke is associated with a higher relative risk of in-hospital death.4,14,15, 23–25
The unadjusted relative risk for death in the hospital due to pneumonia in this study (5.7, 95% CI 5.4–6.0) is similar to that found by Ovbiagele14
(6.4, 95% CI 3.8–10.6) and to the 30-day mortality risks found by Katzan4
(5.9, 95% CI 5.1–6.8) and Saposnik15
(5.18, 95% CI 3.9–6.9). After adjustment the relative risk in this study (2.0, 95% CI 1.9–2.1) is similar to that of Saposnik15
(1.9, 95% CI 1.23–2.95) and lower than the studies by Katzan4
(3.0, 95% CI 2.4–3.7) and Ovbiagale14
(6.0,95% CI 3.0–11.7). Because these differences are more pronounced after adjustment they likely arise because of differences between the samples, models, and methods used.
The finding that the adjusted relative risk for death associated with pneumonia is inversely related to propensity for pneumonia did not support the initial hypothesis. One potential reason can be seen in where the propensity for pneumonia is associated with greater burden of illness. It is possible that the marginal risk for mortality associated with pneumonia in those with the greatest illness burden is blunted by the higher mortality risk that is shared within propensity quintile. Mortality increases as the propensity for pneumonia increases even among those who did not have a diagnosis of pneumonia. A similar phenomenon is seen with a secondary diagnosis of acute myocardial infarction. It is possible that the greater burden of illness in the highest risk group also accounts for the greater incremental cost of hospitalization associated with pneumonia that is greater than the other quintiles in both regardless of diagnosis of pneumonia. The greater proportion of hospitalizations with mechanical ventilation and enteral or parenteral nutrition in those with pneumonia in the highest risk group provides some insight into the additional burden of illness and required level of care that likely contributes to the costs.
The inverse relationship of propensity for pneumonia and the magnitude of the relative risk for death is an important finding when considering how to approach screening for dysphagia in stroke survivors. This study suggests that screening for dysphagia is important regardless of the apparent risks for pneumonia. The number of cases of pneumonia that need to be prevented to prevent one death is similar for the quintiles two through five, accounting for 80% of the hospitalizations. The idea that patient selection can offer the key to utilization of appropriate screening techniques may be more difficult to apply than previously thought, if not misguided altogether. It is possible that a better choice would be to screen all stroke survivors by the most sensitive test available. Pneumonia confers a greater monetary cost for those patients with the highest risk of pneumonia yet greater risk of mortality in those patients who appear to have the lowest risk of pneumonia.
There are several limitations to this study. First, secondary data of this sort have inherent problem of relying on physicians or coders to correctly document diagnoses. It is likely that some diagnoses that may not seem salient to the hospitalization at hand are not recorded yet may have improved the estimates from these analyses had they been. While it would be preferable to have the ability to perform a quality-check on the diagnostic codes within the dataset it is not possible within this dataset. Second, the unit of analysis for the NIS is the hospitalization and not the individual and multiple hospitalizations by the same person could be present within the data. There is no way to estimate how often repeat admissions occur within the data. The results are still representative of hospitalizations occurring within this group and thus provide insight as to where efforts might be best spent for prevention of pneumonia. Finally, risk in this study is based on statistical methods of a limited number of after the fact diagnoses that may not accurately represent the risk that practitioners are able to estimate by clinical examination. It would have been ideal to have such information to include in this study but that was not possible with the data sources utilized for this study.
Many questions remain to be answered about pneumonia prevention after stroke. Foremost, it is not clear how well dysphagia treatments prevent pneumonia. In practice, multiple treatments and strategies are utilized in various combinations in attempt to decrease aspiration, and treatments are often tailored to the individual. One study evaluated the incidence of pneumonia in a population with stroke after implementation of a comprehensive dysphagia treatment program resulted in a 3 month incidence of pneumonia of 1.8%, considerably lower than the 8.1% prevalence found in this study.11
Two studies have shown that a formal dysphagia screening program reduces aspiration pneumonia, and one completely eliminated it, though the diagnostic criteria for aspiration pneumonia are not provided. 24, 26
It is also not clear, if it is presumed that dysphagia treatment is effective, which screening method is best. While the videofluoroscopic swallowing study is considered the best instrument for diagnosing dysphagia and determining the best treatment the examination protocol has not been standardized and thus effectiveness is likely to vary.27
It’s also not clear whether using such a method for dysphagia screening in all stroke survivors would be cost-effective.