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Aging and asthma: pathophysiological mechanisms

Asthma is common in all age groups and emerges as significant problem for elderly people ( 1 1–5). It is often underperceived, underdiagnosed, and undertreated (6, 7). There are several reports of acute, severe asthma in this age group (8, 9). From the clinical perspective, asthma in an elderly person may be difficult to diagnose because of lower sensitivity to symptoms, nonspecific presentation, and the frequently confounding effect of comorbidity. The latter can, in turn, increase the severity of the clinical picture and make treatment more difficult (10, 11). Other important issues concerning the treatment of asthma in the elderly relate to changes in pharmacokinetics, a higher risk of untoward effects, and poorer compliance. An important aspect of this phenomenon is the limited ability of this age group to use inhalers (12). Polypharmacy is inherent in treating older people and accurate drug histories are essential for identifying those in whom concurrent treatment may induce bronchospasm or may interact with asthma medication. Morphologic and physiologic abnormalities have been observed in the aging human lung (13). A decrease in mucociliary function, dilatation of the air spaces, loss of elastic recoil, loss of elastin fibers, diminished diffusion capacity, and evidence of low grade inflammation of the respiratory tract have all been found in elderly people. These changes have superimposed effects on those induced by the asthma-related chronic inflammation of the airways, and cannot be without effect on the evolution of the remodeling process in the airways (14–21). Aging also has a profound effect on the immune system and cells that have a regulatory role in asthma (22). A decline in humoral immunity has been documented in older people (23). Advanced age has also been shown to be associated with an increased vulnerability to infectious agents (24). These specific events may depend on many age-related changes in various organ systems, such as environmental factors, nutritional status, and the frequent presence of multiple chronic debilitating diseases. However, it is still unclear whether, and to what extent, immunosenescence plays a role in the increased susceptibility to inflammatory agents involved in the pathogenesis of asthma, and in the dynamics of development of structural airway changes.