Clinical predictors of health-related quality of life depend on asthma severity

The National Asthma Education and Prevention Program guidelines define asth ma severity before treatment by lung function and symptoms. It has been ass umed, but not demonstrated, that improvement in these measures would transl ate into improvement in health-related quality of life (HRQL), Because HRQL is an important outcome in asthma management, we asked what are the determ inants of HRQL? To address this question, we retrospectively analyzed HRQL data, as measured by the juniper Asthma Quality of Life Questionnaire, in s ubjects with mild versus moderate-severe asthma from two clinical trials. W e examined whether these traditional clinical outcomes have different relat ionships to HRQL depending on asthma severity. We also assessed whether the relationship between clinical outcomes and HRQL in subjects with moderate- severe asthma would change when subjects improved to mild-moderate disease with controller medication treatment. Lung function was not an independent predictor or determinant of HRQL at any level of asthma severity, whereas i ntensity of shortness of breath predicted HRQL at all levels of asthma seve rity. Rescue beta -agonist use independently predicted HRQL in subjects wit h mild asthma, but not in those with moderate-severe asthma, In subjects wi th moderate-severe asthma who improved to mild-moderate disease with contro ller treatment, rescue beta -agonist use predicted HRQL. We conclude that t he independent determinants of HRQL vary according to asthma severity and c hange with asthma treatment.