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An evaluation of the determinants of asthma management and asthma control : a study of British Columbia asthmatics Lynd, Larry David


Objectives: The primary objective of this study was to assess the relationship between socioeconomic status and the magnitude of short-acting β-agonist use and asthma control. The primary hypothesis of this study was that lower socioeconomic status asthmatics are more likely to use greater amounts of short-acting β-agonist medications and experience poorer asthma control than asthmatics in higher social classes, independent of asthma severity. Methods: Retrospective administrative data was used to evaluate the association between inappropriate asthma management and health care resource utilization, and to assess trends in asthma medication use between 1996 and 1998 in British Columbia. Using camouflaged sampling and volunteer recruitment, 202 asthmatics between 19 and 50 years of age were recruited for direct assessment to evaluate the relationship between socioeconomic status and asthma control, adjusting for asthma severity. Recruiting rates of camouflaged sampling were evaluated, and characteristics of sampled participants and volunteers were compared. Asthma control was measured using the magnitude of short-acting β-agonist use, and the Asthma Control Questionnaire. Five methods of adjusting for asthma severity were used. Socioeconomic status was measured at the individual level based on self-reported income, education, and receipt of social assistance, and at the population level according to neighbourhood median household income, proportion of neighbourhood with at least a bachelor's degree, and neighbourhood unemployment rate. Results: Initial analyses of administrative data revealed that inappropriately managed asthmatics utilize more health care resources relative to appropriately managed asthmatics. Longitudinal analysis of Pharmacare prescription data did not reveal any reduction in short-acting β-agonist use or increase in inhaled corticosteroid use. Asthmatics receiving social assistance were more likely to increase their use of SA β-agonists versus those who were not. Independent of the method of measuring socioeconomic status or adjusting for asthma severity, less education, lower income, and receipt of social assistance were consistently associated with the use greater amounts of SA β-agonists independent of asthma severity, and to have more poorly controlled asthma based on the Asthma Control Questionnaire. Population measures of socioeconomic status revealed similar and consistent relationships. Conclusions: Inappropriately treated asthmatics in BC utilize more health care resources, and the excessive use of SA β-agonist medications persists. Camouflaged sampling resulted in a more heterogenous sample of SA β-agonist users compared to voluntary recruitment. Socioeconomic status is strongly and consistently negatively associated with the magnitude of SA β-agonist use, independent of asthma severity, and is positively associated with asthma control. Improvements in asthma control in lower social class asthmatics may result in a narrowing of the social gradient in asthma-related outcomes.

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