Coexistent chronic conditions and asthma quality of life: a population-based study.

OBJECTIVE: Reports of the prevalence and impact of comorbid conditions among people with asthma have been limited to certain population groups or convenience samples. Our aim was to examine the prevalence of major comorbidity in asthma and associations with quality of life and functional status in the general population. STUDY DESIGN/
SETTING: The WANTS Health and Well-being Survey is a cross-sectional representative population household telephone interview survey in three Australian states. PARTICIPANTS: Representative sample of noninstitutionalized adults in three Australian states. MEASUREMENT AND
RESULTS: From the available sample of 10,080 patients, 7,619 interviews were completed (participation rate, 74.8%), with 834 people reporting current doctor-diagnosed asthma (11.2%). People with asthma were more likely to report one of the selected comorbid conditions: diabetes, arthritis, heart disease, stroke, cancer, osteoporosis (adjusted odds ratio, 1.9; 95% confidence interval, 1.5 to 2.2). Among people with asthma, there were statistically and clinically significant decreases in usual activity levels and in Short Form-12 physical component summary scores when another chronic condition was also present. For those with any of the chronic conditions, the additional presence of asthma was associated with significant further impairment in quality of life in those aged > 35 years but not in younger adults.
CONCLUSION: The significant reduction in quality of life associated with comorbidity in asthma has implications for disease management and organization of care, as well as for the design and external validity of single-disease clinical trials.