Association of airway hyperresponsiveness with reduced quality of life in patients with moderate to severe asthma.

BACKGROUND: Airway hyperresponsiveness (AHR) is an indicator of poor asthma control. Asthma patients with AHR to methacholine have been shown to have a poorer quality of life compared with asthma patients without AHR, but it is not clear to what degree this is a result of more severe disease in patients with AHR.
OBJECTIVES: To describe the relationship between AHR and quality of life in asthma patients and to determine the impact of the severity of asthma on this relationship.
METHODS: Data from 691 asthma patients were analyzed to describe the relationship between the impact of AHR to methacholine (cumulative dose of methacholine required to provoke a 20% decrease in forced expiratory volume in 1 second, < or = 8 micromol) on quality of life (measured by the Asthma Quality of Life Questionnaire) of asthma patients in relation to the severity of asthma (according to the Global Initiative for Asthma guidelines).
RESULTS: Asthma patients with AHR had more severe asthma and a poorer quality of life compared with asthma patients without AHR. Furthermore, the quality of life decreased with increasing severity of asthma. However, regression analysis showed an independent association between both the presence of AHR and the severity of asthma and quality of life, as well as an interaction between the effects of these 2 factors. Finally, subgroup analysis showed that the impact of AHR on the quality of life was only clinically significant in moderate to severe asthma but not in mild asthma.
CONCLUSIONS: AHR is associated with a negative impact on the quality of life of asthma patients that is partly independent of the severity of asthma.