Airway hyperresponsiveness in the elderly: prevalence and clinical implications

Airway hyperresponsiveness is associated with an increased risk of developing respiratory symptoms. The assessment of airway hyperresponsiveness can provide valuable information regarding the natural course of respiratory diseases. However, little information is available for populations of more advanced age, and data are conflicting. It was assessed whether age influences the occurrence of airway hyperresponsiveness by reviewing those studies that specifically addressed this issue, and attempting to identify the factors responsible for discrepancies between studies. Eighteen studies, published between 1983 and 2002, are included in this review. Overall, the results of the analysis are in favour of a positive association between age and airway hyperresponsiveness, the prevalence of which appears to increase in the elderly. The most important determinants were reduced lung function, probably due to geometric factors, and a history of smoking, primarily because of the length of exposure, although acute effects were also demonstrated. Atopy should also be considered as an independent determinant of airway hyperresponsiveness in the elderly population. In addition, inflammatory and neuronal mechanisms could be involved. Finally, the role of sex requires further investigation. Assessing the impact of age on the occurrence of airway hyperresponsiveness has important implications: the age-associated alterations to the lung provide a model for evaluating the contribution of structural changes to the pathogenesis of airway hyperresponsiveness. From a clinical standpoint, evaluation of the magnitude of airway hyperresponsiveness could permit the early identification of individuals who are at risk, even at more advanced age. Assessment of airway hyperresponsiveness in the aged should be considered as an additional tool in the diagnostic work-up in the subset of elderly subjects with long-term smoking exposure and/or documented atopy.