Asthmatic patients frequently have comorbidities, but the role of comorbidities in the economic burden of asthma is unclear. We examined the excess direct medical costs, including asthma- and comorbidity-related costs, in patients with asthma.We created a propensity score-matched cohort of patients newly diagnosed with asthma and non-asthmatic comparison subjects, both aged 5-55 years, from health administrative data (1997-2012) in British Columbia, Canada. Health services use records were categorised into 16 major disease categories based on International Classification of Diseases codes. Excess costs (in 2013 Canadian dollars ($)) were estimated as the adjusted difference in direct medical costs between the two groups.Average overall excess costs were estimated at $1058/person-year (95% CI 1006-1110), of which $134 (95% CI 132-136) was attributable to asthma and $689 (95% CI 649-730) to major comorbidity classes. Psychiatric disorders were the largest component of excess comorbidity costs, followed by digestive disorders, diseases of the nervous system, and respiratory diseases other than asthma. Comorbidity-attributable excess costs greatly increased with age but did not increase over the time course of asthma.These findings suggest that both asthma and comorbidity-related outcomes should be considered in formulating evidence-based policies and guidelines for asthma management.
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