Income-Related Inequity in Initiation of Evidence-Based Therapies Among Patients with Acute Myocardial Infarction

Gillian E. Hanley 1 Steve Morgan 1 Robert J. Reid 0 0 Group Health Research Institute , Seattle, WA, USA 1 Centre for Health Services and Policy Research, School of Population and Public Health, University of British Columbia , Vancouver, BC, Canada BACKGROUND: Previous research has shown a socioeconomic status (SES) gradient in the receipt of cardiac services following acute myocardial infarction (AMI), but much less is known about SES and the use of secondary preventive medicines following AMI. OBJECTIVES: To examine the role of income in initiation of treatment with ACE-inhibitors, beta-blockers and statins in the 120 days following discharge from hospital for first AMI. DESIGN: A cross-sectional study with a populationbased cohort. PARTICIPANTS: First-time AMI patients between age 40 and 100 discharged alive from the hospital and surviving at least 120 days following discharge between January 1, 1999 and September 3, 2006. MAIN MEASURES: Binary variables indicating whether the patient had filled at least one prescription for each of the medicines of interest. KEY RESULTS: Our results reveal a significant and positive income gradient with initiation of the guideline-recommended medicines among male AMI patients. Men in the third income quintile and above were significantly more likely to initiate treatment with any of the medicines than those in the first quintile, with those in the fifth income quintile having 37%, 50% and 71% higher odds of initiating ACEinhibitors, beta-blockers and statins, respectively, than men in the lowest income quintile [OR = 1.37 95% CI (1.24, 1.51); OR = 1.50 95% CI (1.35, 1.68); and OR = 1.71 95% CI (1.53, 190)]. The gradient was not present among women, although women in the fifth income quintile were more likely to initiate betablockers and statins than women in the lowest income quintile [OR = 1.25 95% CI (1.06, 1.47) and OR = 1.32 95% CI (1.12, 1.54)]. CONCLUSIONS: There were inequities in treatment following AMI in the form of a clear and often significant gradient between income and initiation of evidence-based pharmacologic therapies among male patients. This gradient persisted despite significant changes in coverage levels for the costs of these medicines. - Despite Canadas universal health insurance, research has shown that socioeconomic status (SES) affects receipt of cardiac procedures following an acute myocardial infarction (AMI): previous studies have reported that AMI patients with higher SES are more likely to receive cardiac catheterization1,2 and coronary angiography3 than are more disadvantaged patients. Some research has suggested that prescribing for secondary prevention may be influenced by non-clinical factors such as patient age and education4. However, the potential relationship between SES and receipt of recommended prescription medicines following AMI remains unclear. Pharmacologic therapy is safe and effective in the secondary prevention of coronary artery disease. Generally accepted clinical practice guidelines recommend that all patients without contraindications or intolerance be treated with acetylsalicylic acid (ASA), beta-blockers, angiotensin-converting enzyme (ACE) inhibitors and cholesterol-lowering statins57 to prevent secondary events. Guidelines recommend the combined use of all four medicines as each of these agents has been shown to reduce the risk of death and reinfarction810, and combination use provides the largest reduction in risk11. Despite these guidelines, we know that not all eligible AMI patients receive these pharmacotherapies12,13. Given that all first-time AMI patients have the same level of need for these therapies, if the health care system was achieving its stated goals of promoting the use of effective medicines according to need rather than ability-to-pay, we would expect no significant differences in the initiation of recommended treatment following AMI across income groups (as a measure of SES) 14,15. To test this (null) hypothesis, we performed a populationbased province-wide study of the initiation of treatment with ACE-inhibitors, beta-blockers and statins in the 120 days following discharge from the hospital for first AMI in British Columbia (BC). We also sought to determine whether the relationship between income and initiation of these medicines persisted after the drug benefits structure changed in BC. While pharmaceuticals used in outpatient settings are not included in the Canadian universal health insurance plan, prior to May 2003 BC provided relatively comprehensive public drug coverage for seniors (age 65), where seniors were responsible for small co-pays on medicines up to an annual maximum of $200 for low-income seniors and $275 for other seniors, and a catastrophic coverage program for non-seniors (offering 70% coverage after $1,000 and 100% coverage after $4,333). In May 2003, BC moved to a pharmacare program with income-based coinsurance and deductibles regardless of age, which increased the cost of medicines for many seniors in the province16,17. This policy change may have altered associations between income and access to medicines. We performed a cross-sectional study with a population-based cohort. Our data sets include all residents of BC except those whose health care is under federal jurisdiction: registered first nations, veterans, RCMP and inmates of federal penitentiaries (approximately 4% of the total population)18. We were provided data from Population Data BC and the BC PharmaNet with the permission of the BC Ministry of Health Services and the BC College of Pharmacists. Ethics approval was obtained from the Behavioural Research Ethics Board at the University of British Columbia. STUDY POPULATION Figure 1 outlines the exclusion criteria for our study population. Using automated hospital discharge records, we identified all patients who were admitted between January 1, 1999 and September 3, 2006 to any acute care hospital in BC with a primary diagnosis of AMI (ICD version 10 I21.x and ICD version 9 410.x). We restricted our analysis to patients aged 40 to 100 years who were discharged alive between January 1, 1999 and September 3, 2006, and who had no previous diagnosis of AMI during the 5 years prior. We identified previous AMI by searching the hospital data for the 5 years prior to the identified AMI to determine whether the patient had been previously admitted to any acute care hospital in BC with a primary diagnosis of AMI (same codes as above). The first AMI event was considered the index AMI. We used the ICD-10 diagnoses in the hospital discharge data for the index AMI admission to eliminate patients with comorbidities that could be considered contraindications to treatment with one or more of the three medicines of interest. These included cirrhosis, cholestatisis, chronic obstructive pulmonary disorder, asthma, bradycardia, end-stage renal disease and aortic stenosis19. In order to ensure we had accurate health care and prescripti (...truncated)