Preventing Community-Acquired Pneumonia in the Elderly: An Achievable Goal?
ABSTRACT & COMMENTARY
Synopsis: In a prospective case-control trial, aspiration of gastric contents and reduced serum albumin were independent risk factors for pneumonia, while outcome was most affected by whether or not the patient was bedridden, had an underlying swallowing disorder, or was hypothermic on admission.
Source: Riquelme R. Am J Resp Crit Care Med 1996; 154:1450-1455.
Because of the high incidence of pneumonia in patients over age 65, developing strategies to reduce this risk are important goals of clinical medicine. For example, elderly patients have been encouraged to obtain a yearly influenza vaccination and to seek pneumococcal vaccination to reduce rates of influenza and invasive Streptococcus pneumoniae infection.1
Although age and comorbid medical illnesses have been identified as important pneumonia risk factors,2 additional points of effective preventive strategy need to be developed. The prospective study of Riquelme et al examined 101 patients admitted to a Spanish hospital over an eight-month period. Inclusion criteria included a new chest radiograph and at least one major and two minor criteria: cough, sputum, fever, dyspnea, pleuritic pain, consolidation on physical examination, and an elevated white count (12,000 cells/cc). Routine microbiology blood cultures, pleural fluid, and serologies were obtained where applicable, as was a nutritional assessment. Patients admitted to the hospital with pneumonia were generally male (mean age, 78). They had both significant past medical histories of smoking (27-pack years) and alcohol intake. Cardiac disease was the most commonly associated medical illness (38%) compared to COPD (30%), neurologic disorders (26%), and diabetes (17%). The average length of stay was 10 days. Clinical presentation revealed a diminished mental capacity and an elevated white count to be the most significant distinguishing factors of patients with pneumonia compared to controls. Microbial etiology was determined in only 42% of cases, with S. pneumoniae accounting for 30% of identified pathogens (see Table 1). The most important risk factors associated with the development of pneumonia included suspicion of large-volume aspiration, swallowing dysfunction, low serum albumin, prior antibiotics, and malnutrition (see Table 2). Outcome was worsened in patients who were bedridden or had swallowing disorders, or who presented hypothermic. Of less significance was a high respiratory rate, shock, elevated creatinine, hypoxemia, and the number of affected lobes. Non-resolution of pneumonia, defined as radiographic persistence for more than 30 days, was seen in 18% of cases, most commonly associated with pneumococcal and Chlamydia pneumonia. Final radiographic resolution was achieved in between one and two months in all cases. Mortality remained high with a crude mortality rate of 26% and an attributable mortality rate of 20%.
Table 1
Etiologic Diagnosis of Community-Acquired Pneumonia
| Streptococcus pneumoniae | 86% |
| Chlamydia pneumoniae | 17% |
| Coxiella burnetti | 11% |
| Legionella pneumophila | 6% |
| Mycoplasma pneumoniae | 4% |
| Pseudomonas aeruginosa | 2% |
| Proteus mirabilis | 2% |
| Streptococcus viridans | 2% |
| Moraxella catarrhalis | 2% |
| Mixed flora | 2% |
Modified from: Riquelme R, et al. Am J Respir Crit Care Med 1996; 154:1450-1455
COMMENT BY ALAN M. FEIN, MD
Pneumonia is clearly no longer the "old man’s friend." As individuals are living longer with high levels of functional capacity, the challenge for the primary care physician is to maintain a high quality of life for elderly patients. However, following episodes of acute pneumonia, debilitation and reduced activity of daily living are frequently observed for up to six months after the infection. In this large, prospective Spanish study, some hints about modifiable risk factors to prevent pneumonia are offered.
Table 2
Risk Factors for Developing Pneumonia
| Risk Factor Odds Ratio | |
| Suspicion of aspiration | 12.2 |
| Swallowing disorders | 9.78 |
| Low serum albumin | 6.81 |
| Prior antibiotics | 4.91 |
| Malnourishment | 4.61 |
| Low serum prealbumin | 3.34 |
| Quality of life | 3.17 |
| Hypoproteinemia | 2.85 |
| Bedridden | 2.5 |
Modified from: Riquelme R, et al. Am J Respir Crit Care Med 1996; 154:1450-1455.
Drawing on a group of patients with an average age of nearly 80, the authors identified swallowing dysfunction and aspiration risk as potentially preventable factors for the development of pneumonia in the elderly. In addition, reduced serum albumin, which may reflect underlying poor nutrition, also increased the risk of lower respiratory tract infection. Patients with swallowing disorders had a worsening prognosis, confirming the importance of poor underlying functional status as a determinant of outcome in pneumonia. Patients who were bedridden who presented with temperatures below 37°C were more likely to do poorlya finding that may reflect the inability of debilitated patients to mount an adequate systemic inflammatory response. Although most cases remain microbiologically undiagnosed, S. pneumonia was the most commonly identified pathogen.
What is the take-home message from this study? First, physicians must be attentive to elderly patients who have malnutrition, swallowing dysfunction, or other risk factors for aspiration. Elderly patientsespecially those with increased numbers and severity of medical illnessare colonized with a variety of gram-positive and gram-negative pathogens that make prevention of aspiration even more important. Strategies to reduce this risk such as elevating the head of the bed or improving gastric motility may have significant positive effect in preventing pneumonia. Mortality was high, and the most commonly identified pathogen was pneumococcus. This offers a possibility of reduced incidence and better outcome through the use of both influenza and pneumococcal vaccination, which must be increasingly stressed.
In summary, pneumonia in the elderly remains an important cause of mortality and prolonged disability. Age by itself may be less important as a risk factor than malnutrition and swallowing dysfunction. We must focus on these factors if the dismal outcomes of pneumonia are to be improved.
References
1. Bartlett J, Mundy L. Community-acquired pneumonia. N Engl J Med 1995;1618-1624.
2. Cassiere H, Fein A. Current Opinion: Severe community-acquired pneumonia. 1996;2(3):186-191.
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