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(Chest. 2004;126:1161-1168.)
© 2004 American College of Chest Physicians

Reconcilable Differences*

A Cross-sectional Study of the Relationship Between Socioeconomic Status and the Magnitude of Short-Acting ß-Agonist Use in Asthma

Larry D. Lynd, PhD; Andrew J. Sandford, PhD; Erin M. Kelly; Peter D. Paré, MD; Tony R. Bai, MD; J. Mark FitzGerald, MD, FCCP and Aslam H. Anis, PhD

* From the Faculty of Pharmaceutical Sciences (Dr. Lynd), and the Department of Health Care and Epidemiology (Dr. Anis), University of British Columbia, Vancouver, BC, Canada; iCAPTURE Centre (Drs. Sandford, Parè, and Bai, and Ms. Kelly), Providence Health Care, Vancouver, BC, Canada; and the Centre for Clinical Epidemiology and Evaluation (Dr. FitzGerald), Vancouver General Hospital, Vancouver, BC, Canada.

Correspondence to: Aslam H. Anis, PhD, Centre for Health Evaluation and Outcome Sciences, 620–1081 Burrard St, Vancouver, BC, Canada; e-mail: aslam.anis{at}ubc.ca


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Conclusions
 References
 
Study objective: To assess the association between socioeconomic status (SES) and short-acting (SA) ß-agonist use, controlling for asthma severity.

Design: Cross-sectional study.

Setting: Vancouver, BC, Canada.

Participants: Two hundred two asthmatics between 19 years and 50 years of age and residing in the greater Vancouver regional district.

Measurements: The quantity of SA ß-agonist used in the previous year was collected by self-report; pulmonary function and ß-receptor genotype were measured on each participant. SES was measured at both the individual and population levels. Five methods of adjustment for asthma severity were used, as follows: the Canadian Asthma Consensus Guidelines, three previously developed asthma-severity scores, and forward stepwise multiple regression modeling. Polychotomous logistic regression was used to assess all relationships.

Results: Independent of the method used to measure SES or adjust for asthma severity, lower SES was consistently and significantly associated with the use of greater amounts of SA ß-agonist. Adjusting for severity using the multivariate model explained the most variance of SA ß-agonist use (R2 adjusted, 0.35 to 0.37). In this model, social assistance recipients were more likely to use greater amounts of SA ß-agonist (odds ratio [OR], 3.4; 95% confidence interval [CI], 1.7 to 6.5). An inverse relationship between SA ß-agonist use and both annual household income (> $50,000; OR, 0.28; 95% CI, 0.13 to 0.60; and $20,000 to $50,000; OR, 0.44; 95% CI, 0.21 to 0.96; relative to <$20,000) and education (completing a bachelor’s degree vs no formal education; OR, 0.25; 95% CI, 0.14 to 0.71). Participants living in a neighborhood with higher median household income (OR, 0.91; 95% CI, 0.84 to 0.98 per $1,000 increase) or a higher prevalence of having attainted a bachelor’s degree (OR, 0.96; 95% CI, 0.84 to 0.98 per 1% increase) were also less likely use greater amounts of SA ß-agonist. Results were consistent for neighborhood unemployment rate.

Conclusions: The social gradient in asthma-related outcomes may be at least partially attributable to poorer asthma control in lower-SES asthmatics.

Key Words: adrenergic ß-agonists • asthma • severity of illness index • social class


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Conclusions
 References
 
An association between the excessive use of short-acting (SA) ß-agonists and greater asthma-related morbidity and mortality has been identified, raising concerns over their safety. Specifically, asthmatic patients receiving excessive amounts of SA ß-agonist experience more frequent emergency department visits,1 have a greater likelihood of a hospital admission,2 and are at greater risk of having a fatal or near-fatal asthma exacerbation, independent of asthma severity.3 At least four prospective studies4567 have also shown that the regular use of salbutamol and fenoterol is associated with poorer outcomes when compared to their use on an as-needed or rescue basis.

Current asthma management guidelines define good asthma control as requiring less than four doses (eight puffs) of a SA ß-agonist per week.8 In two previous studies,910 we identified a high prevalence of SA ß-agonist use above this threshold, with little or no concomitant inhaled corticosteroid (ICS), suggesting suboptimal management. We therefore embarked on a study of factors related to the excessive use of SA ß-agonists.

Similar to the adverse outcomes reported secondary to SA ß-agonists, asthmatic patients of lower socioeconomic status (SES) also experience more frequent hospital admissions,1112 emergency department visits,1 physician visits,1314 and greater asthma-related mortality.15 Although SES and excessive SA ß-agonist use have been shown to be independently related to similar measures of asthma-related morbidity and mortality, their interrelationship has not been investigated.

Although the social gradient in asthma-related outcomes has been attributed to greater asthma severity,1316 we hypothesized that the social gradient in asthma-related outcomes may be related to poorer asthma control, rather than to asthma severity. The primary objective of this analysis was to assess the relationship between SES and the excessive use of SA ß-agonists as a measure of asthma control, adjusting for asthma severity. Because specific ß-receptor genotypes have also been shown to result in ß-agonist–induced ß2-receptor down-regulation, which clinically could lead to increased tolerance and subsequently increased use, we also evaluated the genotypic predisposition to excessive SA ß-agonist use.


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Conclusions
 References
 
Patient Recruitment and Study Sample
We performed a cross-sectional study of a sample of 202 English-speaking asthmatic patients between 19 years and 50 years of age residing in the Greater Vancouver Regional District of British Columbia (BC), Canada. One hundred nine subjects were recruited from a random sample of SA ß-agonist users identified using the BC Ministry of Health Pharmacare database. Researchers were blinded to the identity of the every patient until the patient consented to participate, thereby protecting each patient’s privacy and ensuring confidentiality. Pharmacare is the pharmaceutical reimbursement program of BC, which provides comprehensive first-dollar coverage for all BC residents on social assistance (plan C), and the general population < 65 years of age (plan E) whose annual family pharmaceutical expenditure exceeds $800 per year. Ninety-three subjects were recruited through media advertising. A detailed description and evaluation of the recruiting method has been published elsewhere.17 Each subject was assessed in a pulmonary research clinic by trained personnel, and received $25 to defray travel expenses. The institutional and university ethics review boards approved the study protocol, and informed consent was obtained from each participant.

Data Collection
Pulmonary function was measured in accordance with American Thoracic Society criteria.18 FEV1 was expressed as a percentage of the value predicted based on the patient’s gender, age, and height.19 All other data were collected by self-report. To control for differences in potency, strength, and formulation, the amount of each specific SA ß-agonist used was standardized to the number of canisters of salbutamol metered-dose inhaler (100 µg/puff, 200 puffs per canister), and each dosage form of ICS was standardized to the equivalent dose of beclomethasone dipropionate by metered-dose inhaler. This dosage standardization methodology has been applied previously.910

Both individual (proximate) and population (contextual) measures of SES were used. Proximate measures were based on self-reported annual household income ($20,000, $20,000 to $50,000, and >$50,000, expressed in Canadian dollars), education (years of postsecondary education and highest level completed), and the receipt of social assistance. Exploratory analysis accounting for family size based on the low-income cutoff was also performed.20 Contextual socioeconomic factors, ie, neighborhood median household income, unemployment rate, and the proportion of residents having received a bachelor’s degree, were derived from the linkage of the postal code of each subject’s current residence with the 1996 BC census data.21

Blood was collected from each subject for DNA extraction from leukocytes. Genotyping for ß2-adrenergic receptor polymorphisms at positions 16 and 27 was done using polymerase chain reaction amplification of the region containing the two polymorphisms followed by restriction endonuclease digestion.22 The associations between genotype and the amount of SA ß-agonist used were compared separately for each locus. Homozygotes for arginine and glycine at position 16 and glutamine at position 27 were compared separately to all other individuals.

Asthma Severity
Four dimensions of asthma have been proposed as measures of asthma severity: symptoms, medication use, degree of airflow obstruction, and asthma-related morbidity (eg, emergency department visit or hospital admission)232425; however, there is currently no "gold standard" for measuring asthma severity. Therefore, we used five different methods to facilitate comparison.

An algorithm based on the Canadian Asthma Guidelines, including whether or not asthma was controlled, asthma medication use (other than SA ß-agonists), the degree of airflow obstruction, and symptoms was used to classify asthma severity as mild, moderate, or severe.8 The magnitude of asthma symptoms was derived from the scores on the symptom and activity domains of the Standardized Asthma Quality of Life Questionnaire (AQLQ[S]).26

Three interval score measures of asthma severity, each based on different dimensions of asthma severity, were also used. The asthma symptom sum (ASS) is a summed score of patient-rated severity of wheeze, shortness of breath, cough, and chest tightness.27 The chronic lung disease severity index (CLDSI) is a validated summed score proposed for use in asthma, emphysema, and chronic bronchitis derived from the frequency of shortness of breath, wheeze, cough, and sputum production.28 Each component of the ASS and CLDSI is included in the AQLQ(S). Therefore, these scores were derived from the corresponding AQLQ(S) questions, resulting in final severity scores ranging from 4 to 28, with higher scores representing less severe disease.

Ng29 proposed a score (referred to as the Ng Score) ranging from 3 (least severe) to 10 based on the frequency of daytime and nocturnal symptoms, and the percentage of predicted FEV1. Final scores were reverse coded to correspond with the direction of the ASS and CLDSI.

Finally, a specific model incorporating all variables related to each proposed dimension of asthma severity was developed with the amount of SA ß-agonist use as the dependent variable. Initially, separate models were developed for the dimensions of symptoms, morbidity, airway obstruction, and asthma medication use (other than SA ß-agonists) using forward stepwise multiple polychotomous logistic regression. All significant variables from each dimension model were then incorporated into a final forward stepwise regression model, yielding a final model of all severity-related factors that best explained the magnitude of SA ß-agonist use.

Statistical Analysis
The relationship between SA ß-agonist use and SES, controlling for asthma severity, was evaluated using polychotomous logistic regression.30 The dependent variable was the ordinally classified number of standardized canisters of SA ß-agonist used in the previous year. Each individual was classified as a low (< 4 canisters), intermediate (4 to 12 canisters), or high (> 12 canisters) user. A cumulative logit model was used that assumes that the log-cumulative odds are proportional, or that the odds of a response above a given response level are constant, independent of the cut point chosen.30 To ensure the maximal explanation of the variance of SA ß-agonist use attributable to asthma severity, any dimension of severity not included in a specific severity score was added to the model prior to adding the SES variable, and prior to the evaluation of all potential interactions.25

The proportional odds assumption was tested for each model using a Score test.30 If the hypothesis of proportional odds was rejected (p < 0.05), each group comparison (high vs low/intermediate use and intermediate/high vs low use) was modeled separately using binary logistic regression.

Model fit was assessed based on the minimization of the – 2 log likelihood and maximization of the adjusted R2. Entry criterion for forward step-wise variable selection was set at p < 0.10. Odds ratios (ORs) and 95% confidence intervals (CIs) for having used a greater amount of SA ß-agonist (ie, ≤ 4 canisters vs > 4 canisters, or ≤ 12 canisters vs > 12 canisters) are reported for each association.


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Conclusions
 References
 
The distribution and univariate analyses of factors postulated a priori to be associated with SA ß-agonist use are summarized in Table 1 . The sample was comprised of 50% more women than men, and age was normally distributed across the entire range (median, 39.0 years; range, 19 to 50 years).


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  		Table 1. Univariate Analysis of the Association Between Demographic and SES Factors and the Use of Greater Amounts of SA ß-Agonist (n = 202)*

 
The sample was representative of all levels of asthma medication use and SES, and all participants reported having received at least some SA ß-agonist in the previous year. Twenty-nine patients either did not know or preferred not to provide their annual household income and were therefore excluded from the analysis of income at the proximate level. Thirty-eight patients (23%) reported incomes > $70,000, 18 of which were > $100,000. One hundred twenty patients (59%) and 31 patients (15%) completed at least 1 year and 5 years of postsecondary education, respectively. The sample was also very contextually heterogeneous, with participants residing in neighborhoods with unemployment rates varying from 3 to 33%, and the prevalence of having received a bachelor’s degree ranging from 3 to 53%.

This sample was well distributed across all levels of asthma severity (Table 2 ). All three severity scores were normally distributed across the entire range of the score, with the Ng Score encompassing its entire range, while the CLDSI and ASS ranged from 5 and 6 to 28, respectively. Table 2 also illustrates the construct validity of each severity score. According to the Canadian Asthma Guidelines, patients with moderate and severe asthma were significantly more likely to have used a greater amounts of SA ß-agonists, whereas those with higher asthma severity scores (ie, less severe disease) were less likely to have used greater amounts of SA ß-agonist. Furthermore, as postulated, having visited an emergency department or been hospitalized were also positively associated with SA ß-agonist use, and the better one’s pulmonary function, the less likely they were to use greater amounts of SA ß-agonist.


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  		Table 2. Univariate Analysis of the Associations Between Asthma Severity Scores and Dimensions and the Use of Greater Amounts of SA ß-Agonist*

 
There was no significant association between age, gender, or genotype and the amount of a SA ß-agonist used. Corticosteroid use, all indexes and dimensions of asthma severity, except having been hospitalized for asthma in the previous year, and all proximate and contextual measures of SES were significantly associated with SA ß-agonist use.

Independent of the method used for adjusting for asthma severity, lower SES was associated with using greater amounts of a SA ß-agonist. Patients receiving social assistance were at least 2.5 times more likely to have received greater amounts of SA ß-agonist (Fig 1 ). Adjusting for asthma severity using the Canadian Asthma Guidelines, measuring SES using the receipt of social assistance or annual household income accounted for only 22% and 24% of the variance in the magnitude of SA ß-agonist use, respectively. Conversely, using any of the asthma severity scores to adjust for asthma severity, and any metric of SES explained between 33 to 37% of the variance of SA ß-agonist use. Adding genotype to each final model did not affect the parameter estimates for any variables and reduced the adjusted R2 of each model, and therefore was not included in the final models.



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  		Figure 1. Association between receipt of social assistance and the use of greater amounts of SA ß-agonist, adjusted for asthma severity. ORs are for those individuals receiving social assistance relative to those not receiving social assistance. *Adjusted for emergency department visit in previous year. {dagger}Adjusted for emergency department visit in previous year, daily ICS use (yes/no), daily ICS dose. {ddagger}Model includes emergency department visit in previous year, daily ICS use, frequency of daytime symptoms, and AQLQ(S) symptom score. §The distance between the ORs of 0 to 1 is not equal to the distance for 1-U increase in the ORs > 1 because while a decreased risk can only be represented by a value between 0 and 1, an increased risk can be any value between 1 and {infty} (Fig 2).

 
Both annual household income and level of education completed were negatively and significantly associated with the magnitude of SA ß-agonist used, with a consistent gradient across social classes (Fig 2 ). Adjustment for family size based on the low-income cutoff did not affect the results. Although the gradient based on education was consistent and the overall associations were significant (p < 0.05), the effect of having received only a high school diploma or trades certificate did not differ from unity in any model. However, subjects completing at least a bachelor’s degree were significantly less likely to have used higher doses of a SA ß-agonist in the previous year than those not completing at least a high school diploma.



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  		Figure 2. Association between annual household income and education and the use of greater amounts of SA ß-agonist, adjusted for asthma severity. *Adjusted for emergency department visit in previous year (yes/no). {dagger}Adjusted for emergency department visit in previous year (yes/no), daily ICS use (yes/no), and daily ICS dose. {ddagger}Model includes emergency department visit in previous year (yes/no), daily ICS use (yes/no), frequency of daytime symptoms, and AQLQ(S) symptom score. §See footnote, Figure 1. Adjusting for asthma severity using the Canadian Asthma Guidelines, the OR for using greater amounts of SA ß-agonist for those with annual household incomes between $20,000 and $50,000 was 0.42 (95% CI, 0.20, 0.87) relative to those with annual household incomes < $20,000, and was 0.30 (95% CI, 0.15 to 0.62) for those with annual household incomes > $50,000 relative to those with annual household incomes < $20,000. Overall associations between education completed and SA ß-agonist use are as follows: asthma guidelines, p = 0.009; ASS and CLDSI, p = 0.02; Ng Score, p = 0.004; stepwise model, p = 0.01.

 
The hypothesis of proportional odds was rejected in the models of years of postsecondary education; therefore, comparisons of ß-agonist use groups were modeled separately (Table 3 ). Each additional year of postsecondary education resulted in approximately a 20% reduction in the OR for having used > 4 canisters of SA ß-agonist in the previous year, and approximately a 35% reduction in the OR for having used > 12 canisters.


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  		Table 3. Association Between the No. of Years of Postsecondary Education and the Use of Greater Amounts of SA ß-Agonist, Adjusted for Asthma Severity

 
The associations between all contextual measures of SES and the magnitude of SA ß-agonist use were also significant and consistent in magnitude, independent of method of asthma-severity adjustment. For every $1,000 increase in median neighborhood household income, there was approximately a 10% decrease in the risk of using greater amounts of SA ß-agonist (OR, 0.91; 95% CI, 0.84 to 0.98), and nearly a 5% decrease with every 1% greater prevalence of a having completed a university degree (OR, 0.96; 95% CI, 0.93 to 0.99). The association between SA ß-agonist use and neighborhood unemployment rate was also consistent (OR, 1.1; 95% CI, 1.03 to 1.2).


   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Conclusions
 References
 
Although there was no association between age, gender, or genotype and SA ß-agonist use, we identified a strong and significant association between SES and the amount of SA ß-agonist medications used by asthmatics, independent of asthma severity. This association was consistent across all proximate and contextual measures of SES, with gradients identified in the expected directions. This study provides the first evidence suggesting that poorer outcomes in lower SES asthmatics may not be associated solely with greater asthma severity as previously postulated, but rather also to poorer asthma control, despite universal access to health care.

Three studies313233 that have reported a higher prevalence of more severe asthma in lower-SES children measured asthma severity based on symptoms alone, and may therefore be demonstrating poorer control rather than greater severity. The two studies1316 that have attributed poorer outcomes in lower-SES patients with asthma specifically to greater severity have significant limitations. Using survey data, Littlejohns and McDonald16 found that adults in the lower two quintiles of SES based on the Registrar General’s classification of occupation were twice as likely to have disabling asthma, defined as "severe or frequent bouts of breathlessness, wheezing, or coughing which limit daily activities" as those in the upper 40%. This definition of greater severity could also represent poorer control. Similarly, a Canadian study13 based on administrative health-care data found that low-income adults were admitted to hospital more frequently, had more physician contacts, and were less likely to be assessed by a specialist, without any evidence of more fragmented care or a higher prevalence of asthma in the lower classes. Thus, without any metric for asthma severity, these authors deducted that the lower-income asthmatic patients had more severe disease. By directly assessing patients, we were able to overcome these limitations, and the negligible differences in the crude and adjusted ORs for SES suggest that confounding by disease severity may be less than expected.

Connolly et al34 reported poorer asthma control based on a greater reversibility of airway disease in men in lower social classes. The only studies to assess differential pharmacologic management are two US studies3536 done in children and adolescents, both of which concluded that asthma management may be inadequate in lower social classes. The likelihood that different factors impact asthma control in children and adults prevents the direct extrapolation of these results to adult asthmatics. Furthermore, if access to health care is an important etiologic factor, class differences in access to health care between the US and Canada may mean a lesser likelihood of a social gradient in a Canadian population. The persistence of the association in individuals in our study receiving social assistance suggests that barriers to health care are not the primary etiologic factor in poorer management, given their receipt of essentially all asthma medications and health-care services at no charge.

Previous studies37383940 have shown that specific mutations at amino acid positions 16 and 27 render these individuals prone to ß-adrenergic receptor down-regulation with persistent use of SA ß-agonists. Because this would result in asthmatic patients with these genotypes being less responsive to the bronchodilatory effects of SA ß-agonists, we hypothesized that asthmatics homozygous for glycine at position 16 or glutamine at position 27 would be more likely to use greater amounts of SA ß-agonists. However, there was no association between excessive use of SA ß-agonist and genotype at either locus, suggesting that other factors (eg, social or environmental) play a more predominant role in determining the magnitude of SA ß-agonist use clinically.

By design, this sample was very heterogeneous for asthma severity, SES, and drug utilization. Although the distributions of these variables are not representative of the population distributions, this methodology facilitated the recruitment of a smaller sample size to test our hypothesis. This does raise concerns of a potential volunteer bias if uncontrolled asthmatics from either extreme of SES were more likely to participate. Evidence of differential health beliefs, health management strategies, and perceptions of ability to control one’s disease suggest that uncontrolled asthmatics of higher SES would be more likely to participate in an attempt to increase their knowledge and achieve better control, which would result in conservative estimates of all ORs.41 The potential for the misclassification of SES to bias the results must also be considered; however, this most commonly manifests as upward misclassification of lower social classes, which would also result in conservatively biased estimates of the magnitude of the associations.

An assumption of this analysis is that the excessive use of SA ß-agonists is synonymous with asthma control, an assumption that is supported by both the metrics of control included in the current asthma management guidelines and the Asthma Control Questionnaire, and expert opinion.82542 These results are also dependent on the measurement and adjustment for asthma severity. The quantification of severity is complicated by the complex relationship between asthma severity and asthma control, and thus many of attributes deemed explanatory of asthma severity (eg, symptoms, pulmonary function, and morbidity) are also representative of asthma control. Although we agree with Cockroft and Swystyn25 that ideally asthma severity should be quantified based on the magnitude of treatment required to control symptoms, this was not possible due to the cross-sectional nature of our study. Therefore, it was necessary for us to adjust for asthma severity based on all proposed dimensions of asthma severity including symptoms, pulmonary function, morbidity, and controller medication use. Therefore, the only variable that can truly be used to quantify asthma control in this population is the magnitude of short-acting ß agonist use. If adequately controlled, only the most severe, treatment recalcitrant asthmatics should be using more than four doses of short-acting ß agonist per week independent of asthma severity. No participant in this study could be considered treatment resistant, and therefore short-acting ß agonist use is a valid measure of treatment control in all study participants.

Because there is currently no "gold standard" for measuring asthma severity, we applied five different methods of controlling for asthma severity, and each model included additional measures of any proposed dimension of asthma severity not included in the score. This maximized the variance of SA ß-agonist explained by all dimensions of severity prior to adding SES to the model. The consistency of this approach with the theoretical framework of quantifying asthma severity, of the results across all methods of severity adjustment, and the presence of a gradient across income and education strengthen our conclusions.


   Conclusions
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusions
References
 
These results and our previous analysis support our hypothesis of a social gradient in asthma control, independent of asthma severity.9 This consequentially leads to the hypothesis that improving asthma management in lower social classes may result in a narrowing of the gap in asthma-related outcomes. The determination of the SES-related etiologic factors of inadequate asthma management, such as health beliefs, health behaviors, self-esteem, motivation, knowledge, economic barriers, and medical system management, will be the next step in developing programs and strategies to reduce the social gradient in asthma-related outcomes.


   Acknowledgements
 
We thank Barbara Moore and Drs. Eduardo Hernandez and Georgina Lopez for their assessment of the study participants, and Ms. Dianne Calbick for administrative assistance in the completion of this project.


   Footnotes
 
Abbreviations: AQLQ(S) = Asthma Quality of Life Questionnaire (Standardized); ASS = asthma symptom sum; BC = British Columbia; CI = confidence interval; CLDSI = Chronic Lung Disease Severity Index; ICS = inhaled corticosteroid; OR = odds ratio; SA = short-acting; SES = socioeconomic status

This work was performed at the Centre for Health Evaluation and Outcome Sciences, Providence Health Care; and the Department of Health Care and Epidemiology, University of British Columbia, Vancouver, BC, Canada.

This work was supported by grants from the British Columbia Lung Association and Providence Health Care, Vancouver, British Columbia.

Dr. Lynd was the recipient of a Canadian Institute for Health Research doctoral fellowship and a Michael Smith Foundation for Health Research/British Columbia Medical Services Foundation trainee award at the time of the study.

Received for publication September 25, 2003. Accepted for publication May 10, 2004.


   References
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 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusions
 References
 

  1. Friday, GA, Khine, H, Ling, LS, et al (1997) Profile of children requiring emergency treatment for asthma. Ann Allergy Asthma Immunol 78,221-224[ISI][Medline]
  2. Griffiths, C, Naish, J, Sturdy, P, et al Prescribing and hospital admission for asthma in east London. BMJ 1996;312,481-482[Free Full Text]
  3. Spitzer, W, Suissa, S, Ernst, P, et al The use of beta-agonists and the risk of death and near death from asthma. N Engl J Med 1992;326,501-506[Abstract]
  4. Sears, MR, Taylor, DR, Print, CG, et al Regular inhaled beta-agonist treatment in bronchial asthma. Lancet 1990;336,1391-1396[CrossRef][ISI][Medline]
  5. Van Ganse, E, van der Linden, PD, Leufkens, HG, et al Asthma medications and disease exacerbations: an epidemiological study as a method for asthma surveillance. Eur Respir J 1995;8,1856-1860[Abstract]
  6. Taylor, D, Sears, M, Herbison, G, et al Regular inhaled ß-agonist in asthma: effects on exacerbations and lung function. Thorax 1993;48,134-138[Abstract]
  7. van Schayck, CP, Dompeling, E, van Herwaarden Cees, L, et al Bronchodilator treatment in moderate asthma or chronic bronchitis: continuous or on demand? A randomized controlled study. BMJ 1991;303,1426-1430[ISI][Medline]
  8. Boulet, L-P, Becker, A, Bérubé, D, et al Canadian asthma consensus report, 1999. Can Med Assoc J 1999;161(11 Suppl),S1-S62
  9. Lynd, LD, Guh, DP, Pare, PD, et al Patterns of inhaled asthma medication use: a 3-year longitudinal analysis of prescription claims data from British Columbia, Canada. Chest 2002;122,1973-1981[Abstract/Free Full Text]
  10. Anis, A, Lynd, L, Wang, X, et al Double trouble: inappropriate asthma medication use linked to increased use of health care resources. Can Med Assoc J 2001;164,625-631[Abstract/Free Full Text]
  11. Watson, J, Cowen, P, Lewis, R The relationship between asthma admission rates, routes of admission, and socioeconomic deprivation. Eur Respir J 1996;9,2087-2093[Abstract]
  12. Chen, Y, Dales, R, Krewski, D Asthma and the risk of hospitalization in Canada: the role of socioeconomic and demographic factors. Chest 2001;119,708-713[Abstract/Free Full Text]
  13. Erzen, D, Carriere, K, Dik, N, et al Income level and asthma prevalence and care patterns. Am J Respir Crit Care Med 1997;155,1060-1065[Abstract]
  14. Boulet, LP, Belanger, M, Lajoie, P Characteristics of subjects with a high frequency of emergency visits for asthma. Am J Emerg Med 1996;14,623-628[CrossRef][ISI][Medline]
  15. Higgins, B, Britton, J Geographical and social class effects on asthma mortality in England and Wales. Respir Med 1995;89,341-346[CrossRef][ISI][Medline]
  16. Littlejohns, P, Macdonald, LD The relationship between severe asthma and social class. Respir Med 1993;87,139-143[CrossRef][ISI][Medline]
  17. Lynd, LD, Warren, LD, Maclure, M, et al Using administrative healthcare data to recruit study subjects: experience with "camouflaged sampling." Eur J Epidemiol 2004;19,517-525[CrossRef][ISI][Medline]
  18. American Thoracic Society. Standardization of spirometry–1987 update. Statement of the American Thoracic Society. Am Rev Respir Dis 1987;136,1285-1298[ISI][Medline]
  19. Crapo, RO, Morris, AH, Gardner, RM Reference spirometric values using techniques and equipment that meet ATS recommendations. Am Rev Respir Dis 1981;123,659-664[ISI][Medline]
  20. Cotton C, Webber M, Saint-Pierre Y. Should low income cutoffs be updated? A discussion paper. Ottawa: Income Statistics Division, Statistics Canada, 1999. Report No. 75F0002MIE-99009
  21. BC Stats. Census of Canada. 1998 Ministry of Finance and Corporate Relations. Victoria, BC:
  22. Weir, TD, Mallek, N, Sandford, AJ, et al ß2-Adrenergic receptor haplotypes in mild, moderate and fatal/near fatal asthma. Am J Respir Crit Care Med 1998;158,787-791[Abstract/Free Full Text]
  23. Bailey, WC, Higgins, DM, Richards, BM, et al Asthma severity: a factor analytic investigation. Am J Med 1992;93,263-269[CrossRef][ISI][Medline]
  24. The Joint Task Force on Practice Parameters. Practice parameters for the diagnosis and treatment of asthma. J Allergy Clin Immunol 1995;96,707-870[CrossRef][ISI][Medline]
  25. Cockcroft, DW, Swystun, VA Asthma control versus asthma severity. J Allergy Clin Immunol 1996;98,1016-1018[CrossRef][ISI][Medline]
  26. Juniper, E, Guyatt, G, Epstein, R Evaluation of impairment of health related quality of life in asthma: development of a questionnaire for use in clinical trials. Thorax 1992;47,76-83[Abstract]
  27. Wahlgren, DR, Hovell, MF, Matt, GE, et al Toward a simplified measure of asthma severity for applied research. J Asthma 1997;34,291-303[ISI][Medline]
  28. Selim, AJ, Ren, XS, Fincke, G, et al A symptom-based measure of the severity of chronic lung disease: results from the Veterans Health Study. Chest 1997;111,1607-1614[Abstract/Free Full Text]
  29. Ng, TP Validity of symptom and clinical measures of asthma severity for primary outpatient assessment of adult asthma. Br J Gen Pract 2000;50,7-12[ISI][Medline]
  30. Stokes, M, Davies, C, Koch, G Categorical data analysis using the SAS system. 1995 SAS Institute. Cary, NC:
  31. Mielck, A, Reitmeir, P, Wjst, M Severity of childhood asthma by socioeconomic status. Int J Epidemiol 1996;25,388-393[Abstract/Free Full Text]
  32. Persky, VW, Slezak, J, Contreras, A, et al Relationships of race and socioeconomic status with prevalence, severity, and symptoms of asthma in Chicago school children. Ann Allergy Asthma Immunol 1998;81,266-271[ISI][Medline]
  33. Strachan, DP, Anderson, HR, Limb, ES, et al A national survey of asthma prevalence, severity, and treatment in Great Britain. Arch Dis Child 1994;70,174-178[Abstract]
  34. Connolly, CK, Chan, NS, Prescott, RJ The influence of social factors on the control of asthma. Postgrad Med J 1989;65,282-285[Abstract]
  35. Beausoleil, JL, Weldon, DP, McGeady, SJ ß2-Agonist metered dose inhaler overuse: psychological and demographic profiles. Pediatrics 1997;99,40-43[Abstract/Free Full Text]
  36. Togias, A, Horowitz, E, Joyner, D, et al Evaluating the factors that relate to asthma severity in adolescents. Int Arch Allergy Immunol 1997;113,87-95[ISI][Medline]
  37. Reihsaus, E, Innis, M, MacIntyre, N, et al Mutations in the gene encoding for the beta-adrenergic receptor in normal and asthmatic subjects. Am J Respir Cell Biol 1993;8,334-339[ISI][Medline]
  38. Green, S, Turki, J, Innis, M, et al Amino-terminal polymorphins of the human ß-adrenergic receptor impart distinct agonist promoted regulatory properties. Biochemistry 1994;33,9414-9419[CrossRef][Medline]
  39. Hall, I, Wheatley, A, Wilding, P, et al Association of GLY 27 ß-receptor polymorphism with lower airway reactivity in asthmatic subjects. Lancet 1995;345,1213-1214[CrossRef][ISI][Medline]
  40. Turki, J, Pak, J, Green, S, et al Genetic polymorhpisms of the ß-adrenergic receptor in nocturnal and non-nocturnal asthma. J Clin Invest 1995;95,1635-1641[ISI][Medline]
  41. Gochman, DS Health behavior: emerging research perspectives. 1988 Plenum Press. New York, NY:
  42. Juniper, EF, O’Byrne, PM, Guyatt, GH, et al Development and validation of a questionnaire to measure asthma control. Eur Respir J 1999;14,902-907[Abstract/Free Full Text]



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