The role of immunity and inflammation in lung senescence and susceptibility to infection in the elderly.

Advancing age is associated with a decline in the integrity of physical barriers and protection against invading pathogens, and age-related changes in the immune system are associated with increased susceptibility to the emergence of autoimmune phenomena, neoplasia, and infections. Respiratory tract infections can occur at any age, but the incidence of lower respiratory tract infections increases significantly with advanced age such that pneumonia is a leading cause of illness and death in the elderly. Changes in lung physiology and immune function coupled with inflammation induced by environmental exposures or endogenous factors such as predisposition to aspiration may, in part, account for the increase in susceptibility to respiratory infections. Additionally, age-associated alterations in immune regulation ("immunosenescence") with dysregulation of lung homeostasis may allow low-grade inflammatory changes that lead to anatomical and physiological changes that characterize the senescent lung. The presence of disease states in elderly populations, such as chronic obstructive pulmonary disease (COPD) or nonpulmonary organ system diseases, may increase the likelihood of developing severe respiratory infections. This article examines age-related changes in immune function that predispose elderly individuals to lung remodeling but focuses especially on lower respiratory tract infections. It will discuss risk factors, identify pathogens that typically lead to respiratory infections in the elderly, and review current approaches to treatment and prevention of respiratory infections in the elderly population.