Pneumonia from bacterial and viral agents is the fourth leading cause of death in persons over age 65, accounting for 169.7 deaths per 100,000 persons per year. This high incidence of infection is the result of aging itself as well as age-related coexisting illnesses and their therapies. These factors combine to affect upper and lower respiratory tract host defenses adversely against invading pathogens. Gram-negative colonization of the oropharynx, followed by the spread of bacteria to the tracheobronchial tree, commonly precedes the development of pneumonia. Bacterial adherence is one important and modifiable pathogenetic factor that leads to colonization at both of these sites. Diagnosis of pneumonia in the elderly is often thwarted by difficulties in recognizing infection, as signs and symptoms differ from those observed in younger patients. Therapy is confounded by the frequent inability to obtain adequate culture material to establish a likely pathogen and by altered drug metabolism. In this instance epidemiologic data may be helpful in guiding therapy. Streptococcus pneumoniae is the most common pathogen in community patients, followed by Legionella pneumophila and enteric gram-negative bacilli. Hospitalized and institutionalized individuals are commonly infected with Klebsiella pneumoniae and other enteric gram-negative bacilli, and Legionella pneumophila and Streptococcus pneumoniae are also found. Because recognition of pneumonia may be difficult and therapy is fraught with problems, mortality is high in the elderly. Accordingly, serious attention must be paid to prevention. Prophylaxis includes the use of pneumococcal and influenza vaccines as well as careful attention to the patient's host defense status. Disease states leading to impairment of the immune system should be sought, and efforts should be made to improve host factors that assist the individual in removing invading pathogens.
