Socioeconomic Status and Mortality after Acute Myocardial Infarction

  1. David A. Alter, MD, PhD;
  2. Alice Chong, BS;
  3. Peter C. Austin, PhD;
  4. Cameron Mustard, MD, PhD;
  5. Karey Iron, MHSc;
  6. Jack I. Williams, PhD;
  7. Christopher D. Morgan, MD;
  8. Jack V. Tu, MD, PhD;
  9. Jane Irvine, PhD;
  10. C. David Naylor, MD, DPhil; and
  11. for the SESAMI Study Group*
  1. From the Institute for Clinical Evaluative Sciences, Sunnybrook, Women's College Health Sciences Centre, York University, Institute for Work and Health, and University of Toronto, Toronto, Ontario, Canada.

    Abstract

    Background: Gradients that link socioeconomic status and cardiovascular mortality have been observed in many populations, including those of countries that provide publicly funded comprehensive medical coverage. The intermediary causes of such gradients remain poorly elucidated.

    Objective: To examine the relationships among socioeconomic status, other health factors, and 2-year mortality rates after acute myocardial infarction (MI).

    Design: Prospective cohort study.

    Setting: Ontario, Canada.

    Patients: 3407 patients who were hospitalized for acute MI in 53 large-volume hospitals in Canada from December 1999 to February 2003.

    Measurements: The authors obtained self-reported measures of income and education and developed profiles of the patients' prehospitalization cardiac risks and comorbid conditions. To create these profiles, the authors used the patients' self-reports and retrospectively linked no less than 12 years' worth of previous hospitalization data. Mortality rates 2 years after acute MI were examined with and without sequential risk adjustment for age, sex, ethnicity, social support, cardiovascular history and risk, comorbid conditions, and selected in-hospital process factors.

    Results: Income was strongly and inversely correlated with 2-year mortality rate (crude hazard ratio for high-income vs. low-income tertile, 0.45 [95% CI, 0.35 to 0.57]; P < 0.001). However, after adjustment for age and preexisting cardiovascular events or conventional vascular risk factors, the effect of income was greatly attenuated (adjusted hazard ratio for high-income vs. low-income tertile, 0.77 [CI, 0.54 to 1.10]; P = 0.150). Noncardiovascular comorbid conditions and in-hospital process factors had negligible explanatory effect.

    Limitations: Previous cardiovascular risks were ascertained through self-report or retrospectively through the longitudinal tracking of the hospitals' administrative databases. The study began with a cohort of patients who had an index cardiac event rather than with asymptomatic individuals.

    Conclusions: Age, past cardiovascular events, and current vascular risk factors accounted for most of the income–mortality gradient after acute MI. This observation suggests that the “wealth–health gradient” in cardiovascular mortality may be partially ameliorated by more rigorous management of known risk factors among less affluent persons.

    *For a list of members of the SESAMI Study Group, see the Appendix.

    Article and Author Information

    • Disclaimer: The results, conclusions, and opinions are those of the authors, and no endorsement by the Ministry, the Institute, the Medical Research Council, or the Canadian Institute of Health Research is intended or should be inferred.

    • Acknowledgments: The authors thank Keren Fyman, Shana Kurlandsky, Talia Samson, and Wendy Cooke for their contributions to the coordination and daily operation of the study. The authors also thank the hospitals, physicians, and nurses who participated in the recruitment of patients for the Socio-Economic and Acute Myocardial Infarction study (19, 24).

    • Grant Support: By an operating grant from the Canadian Institutes of Health Research. The SESAMI pilot study was supported by the 1998 Michael Smith Award of Excellence from the Medical Research Council of Canada. The Institute for Clinical Evaluative Sciences is supported in part by a grant from the Ontario Ministry of Health.

    • Potential Financial Conflicts of Interest: Grants received: D.A. Alter (Canadian Institutes of Health Research, Heart and Stroke Foundation of Canada).

    • Requests for Single Reprints: David A. Alter, MD, PhD, Institute for Clinical Evaluative Sciences, 2075 Bayview Avenue, G106, Toronto, Ontario M4N 3M5, Canada; e-mail, david.alter{at}ices.on.ca.

    • Current Author Addresses: Drs. Alter, Austin, Williams, Morgan, and Tu, Ms. Chong, and Ms. Iron: Institute for Clinical Evaluative Services, 2075 Bayview Avenue, G106, Toronto, Ontario M4N 3M5, Canada.

    • Dr. Mustard: Institute for Work and Health, 481 University Avenue, Toronto, Ontario M59 2E9, Canada.

    • Dr. Irvine: York University, 47 Keele Street, Toronto, Ontario M3J 1P3, Canada.

    • Dr. Naylor: University of Toronto, 27 King's College, Toronto, Ontario M5S 1A1, Canada.

    • Author Contributions: Conception and design: D.A. Alter, C. Mustard, K. Iron, J. Irvine, C.D. Naylor.

    • Analysis and interpretation of the data: D.A. Alter, A. Chong, C.D. Naylor.

    • Drafting of the article: D.A. Alter.

    • Critical revision of the article for important intellectual content: D.A. Alter, P.C. Austin, C. Mustard, K. Iron, J.I. Williams, C.D. Morgan, J.V. Tu, J. Irvine, C.D. Naylor.

    • Final approval of the article: D.A. Alter, C. Mustard, J.V. Tu, C.D. Naylor.

    • Provision of study materials or patients: D.A. Alter, C.D. Morgan.

    • Statistical expertise: D.A. Alter, P.C. Austin.

    • Obtaining of funding: D.A. Alter, P.C. Austin, C. Mustard, K. Iron, J.I. Williams, C.D. Morgan, J.V. Tu, J. Irvine, C.D. Naylor.

    • Administrative, technical, or logistic support: D.A. Alter.

    • Collection and assembly of data: D.A. Alter, K. Iron, J.V. Tu.

    Responses to this article

    • Reference Letter#: L06-0111
      • David A. Alter and
      • For the SESAMI study group
      Ann Intern Med published online October 26, 2009
      • Mehdi H. Shishehbor and
      • David Litaker, MD, PhD
      Ann Intern Med published online October 26, 2009

    Summary for Patients

    • Summaries for Patients:The Relationship of Socioeconomic Status and Health Status to Outcomes following Heart Attack Ann Intern Med January 17, 2006 144:I-42
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