Multiple respiratory symptoms predict quality of life in chronic lung disease: A population-based study of Australian adults

Study objectives: Previous studies have shown that it is possible to improve the health-related quality of life (HRQoL) of chronic lung disease (CLD) patients without a concurrent change in morbidity. A valid CLD index that discriminates between different levels of CLD severity and is associated with HRQoL status is an important tool for primary care settings. In this study a symptom-based CLD index was assessed for its validity and relationship with HRQoL in a representative Australian population sample. The study also measured the prevalence of self-reported CLD. Design: Representative population survey of adults aged 18 years and over using a multistage, systematic, clustered area sample. Setting: Metropolitan Adelaide and country centres in South Australia with a population of over 1000 persons. Participants: Three hundred twenty-nine adults with CLD identified through a representative population survey of 3010 South Australians. Measurements and Results: The CLD index and the SF-36 were administered to participants to assess the association between each subscale of the CLD index with each HRQoL scale. The CLD index was also used to assess the prevalence of CLD and the distribution of severity in self-reported CLD in the South Australian population. Each symptom sub-scale of the CLD index was significantly correlated with all scales of the SF-36. The prevalence of CLD as measured by the CLD index was 7.7% (mild), 2.2% (moderate) and 1.0% (severe). Conclusions: In the Australian context the CLD index is a reliable patient interview instrument that can be used to assess the effects of CLD on general HRQoL, improve assessment, and lead to interventions for physicians and their patients.