Pneumonia and host defense in the elderly

The population worldwide continues to age, with those over the age of 80 years constituting the fastest-growing sector of the population. As one ages, infectious complications become more frequent, leading to higher rates of hospitalization. This is also true for the lung, where pneumonia is one of the most frequent causes for hospitalization in the elderly and is the number 3 cause of death in the United States. Several unique changes occur with aging, both in the structure and the function of the respiratory system itself and in the immune system, which increase the predisposition and the potential severity of pneumonia as one ages. In this review, we will highlight the risk factors that are associated with the increased incidence of pneumonia in the elderly and will explore the changes that occur with aging, with focus on the innate and the adaptive immune systems that increase their predisposition to infections.