Psychological factors and asthma quality of life: a population based study

Background: Reports of psychological conditions in asthmatic subjects have been limited to certain population groups or convenience samples. A study was undertaken of the prevalence of psychological distress in asthma in the general population and its associations with quality of life. Methods: The WANTS Health and Well-being Survey is a population household interview survey of adults (age >18) in Western Australia, the Northern Territory, and South Australia. Data obtained were weighted to the closest census data to provide population representative estimates. Positive answers to two questions: "Have you ever been told by a doctor that you have asthma?'' and "Do you still have asthma?'' determined current doctor-diagnosed asthma. Other items included the SF-12, the Kessler-10 index of psychological distress, questions on feelings of lack of control in different areas of life, and on mental health conditions. Results: From the available sample of 10080, 7619 interviews were completed (participation rate 74.8%), with 834 people reporting current doctor-diagnosed asthma (11.2%). Psychological distress was more frequent in those with asthma (17.9% v 12.2%, p<0.01) and a higher proportion with asthma were at higher risk for anxiety or depression (40.5% v 31.2%, p<0.01). Mental health conditions were also more common (16.2% v 10.8%, p<0.01), as was the frequency of those who sometimes or always felt a lack of control over their health (33.5% v 24.3%, p<0.01). People with both asthma and psychological distress had significantly lower scores on the SF-12 physical component summary (PCS) than those with either asthma or distress alone. Among those with psychological distress, mental component summary (MCS) scores did not differ between asthmatic and non-asthmatic respondents. In a multiple regression model the frequency of a feeling of lack of control over health-together with age, family's financial situation, education level, and number of days partially unable to work or perform usual duties-was significantly associated with scores on the PCS (r=0.73, adjusted r(2)=0.54). Conclusion: These results, from a representative population sample, show that psychological distress and decreased feelings of control are common in asthma and are significantly associated with physical health status.