Diabetes Is Not Treated as a Coronary Artery Disease Ri...

Diabetes Is Not Treated as a Coronary Artery Disease Risk Equivalent

Diabetes Is Not Treated as a Coronary Artery Disease Risk Equivalent
Baiju R. Shah, MD, PHD, Janet E. Hux, MD, SM and Peter C. Austin, PHD
Received for publication August 4, 2006. Accepted for publication October 25, 2006

From the Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada

Introduction

Observational studies (1–3) have suggested that the risk of mortality is equivalent for patients with myocardial infarction (MI) without previous diabetes and for diabetic patients without previous MI. Because vascular risk-reduction targets are based on a patient’s future risk, clinical practice guidelines (4–9) recommend that the same or lower blood pressure and lipid targets be applied to diabetic patients as would be applied for secondary prevention following MI. Patients newly diagnosed with diabetes and those with first MIs enter a high-risk category for subsequent coronary events. Therefore, if diabetes were treated as a coronary artery disease risk equivalent, we would expect that both groups of patients should have similar increases in utilization of antihypertensive and lipid-lowering medications following their index events.

Research Design and Methods

The study used administrative health databases from Ontario, Canada, including hospital discharge abstracts, physician service claims, and records from the government drug insurance program, which covers all prescriptions filled for individuals aged ≥65 years. Individuals are linked between databases via an anonymous identification number. The study also used the Ontario Diabetes Database, a validated registry of all individuals with diabetes, derived from these administrative databases (10).

All individuals with no history of MI or diabetes were identified, and two cohorts were assembled: those who either had a first MI or were first diagnosed with diabetes between 1 January 2000 and 31 December 2002, with a 5-year look-back window. Diabetes was determined from the Ontario Diabetes Database (11), while MI was determined from hospital discharge abstracts (12). The observation period for drug utilization for each patient was 800 days before and after the index event. Because the drug benefits program only covered individuals aged &#8805;65 years, those aged <65 at the start of their observation period were excluded. The very elderly (patients &#8805;80 years) were also excluded, as were patients who died before the end of their observation period.

In each of eight 100-day intervals before and after each patient’s index date, we determined whether the patient received at least one prescription for antihypertensive and for lipid-lowering drugs. Prescriptions were counted regardless of indication. For each interval, the proportions of patients in each cohort who received antihypertensive and lipid-lowering drugs were directly standardized for age, sex, and specialist physician care after the index event. To determine whether changes after the index event were different between cohorts, the ratio of drug utilization between each postevent interval and the first pre-event interval was compared between cohorts using bootstrap methods to establish 99% CIs. The research ethics board of Sunnybrook Health Sciences Centre approved the study.

Results

There were 9,742 individuals with incident MI and 38,947 with incident diabetes. Before the index event, patients who subsequently developed diabetes had greater antihypertensive and lipid-lowering drug utilization than patients who subsequently had an MI (Fig. 1). Following the event, antihypertensive drug utilization rose to 96% of individuals with incident MI compared with 75% of those with incident diabetes, while lipid-lowering drug utilization rose to 70 vs. 41%, respectively. These changes in utilization for both drug classes were significantly different between cohorts (P < 0.01) and remained different through all subsequent time intervals (P < 0.01).

Conclusions

Although patients with MIs and with diabetes are at similarly high risk for mortality, utilization of medications to control hypertension and dyslipidemia increased more dramatically following incident MI than following incident diabetes. This difference persisted, although it narrowed over subsequent time intervals.

Several possible explanations can be postulated. The two conditions may be perceived differently: An MI may be viewed as an acute life-changing event, whereas diabetes may be seen as a manageable chronic disease. Since coronary disease risk reduction may have greater relevance for patients who have undergone a coronary event, MI patients and their physicians may be more motivated to initiate and adhere to risk reduction (13). Furthermore, in-hospital MI care is often driven by pathways that may improve prescribing practices (14,15), while diabetes care is usually delivered in the less-structured ambulatory setting. Finally, ongoing acute management issues in diabetes (like glycemic control) may distract patients and physicians from addressing longer-term risk reduction (16).

Other studies have also demonstrated that utilization of cardiovascular therapies in actual clinical practice is not proportional to future risk. For example, lower-risk patients with an acute MI were more likely to receive primary angioplasty (17). Other studies (18–20) have shown that the use of aspirin and statins in the ambulatory setting is associated with predictors of better prognosis. Seniors, who are at particularly high risk following an MI, are less likely to receive thrombolytics, cardiac catheterization, or statins (20–23).

An important limitation of the study is that we did not have patients’ actual blood pressure and lipid measurements, so we could not assess the appropriateness of therapy. However, antihypertensive and lipid-lowering drug utilization before the index event (when all patients were free of both MI and diabetes) was greater among patients who went on to develop diabetes than among those who subsequently had an MI, suggesting that, to begin with, their blood pressure and lipid levels were actually higher. Since treatment targets after the diagnosis of diabetes are at least as aggressive as targets after an MI, any potential differences in the unmeasured clinical variables would, if anything, bias the results in the opposite direction to the observed findings.

The use of coronary disease risk-modifying medications by individuals with incident diabetes is reduced compared with those with incident MI, despite having similar or stricter blood pressure and lipid targets. In clinical practice, diabetes is not treated as a coronary artery disease risk equivalent. The undertreatment of coronary risk factors for diabetic patients is an important gap in the quality of care of these high-risk patients.

Acknowledgments

The Canadian Institutes of Health Research supports B.R.S as a Clinician Scientist.

Footnotes

A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C Section 1734 solely to indicate this fact.

Received for publication August 4, 2006. Accepted for publication October 25, 2006.

References

# Haffner SM, Lehto S, Ronnemaa T, Pyorala K, Laakso M: Mortality from coronary heart disease in subjects with type 2 diabetes and in nondiabetic subjects with and without prior myocardial infarction. N Engl J Med 339:229–234, 1998[Abstract/Free Full Text]
# Vaccaro O, Eberly LE, Neaton JD, Yang L, Riccardi G, Stamler J, the Multiple Risk Factor Intervention Trial Research Group: Impact of diabetes and previous myocardial infarction on long-term survival: 25-year mortality follow-up of primary screenees of the Multiple Risk Factor Intervention Trial. Arch Intern Med 164:1438–1443, 2004[Abstract/Free Full Text]
# Juutilainen A, Lehto S, Ronnemaa T, Pyorala K, Laakso M: Type 2 diabetes as a "coronary heart disease equivalent": an 18-year prospective population-based study in Finnish subjects. Diabetes Care 28:2901–2907, 2005[Abstract/Free Full Text]
# National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Choleserol in Adults (Adult Treatment Panel III): Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). Washington, DC, National Institutes of Health, 2002, (NIH publ. no. 02-5215)
# National High Blood Pressure Education Program: The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure. Washington, DC, National Institutes of Health, 2004, (NIH publ. no. 04-5230)
# American Diabetes Association: Standards of medical care in diabetes–2006. Diabetes Care 29(Suppl. 1):S4–S42, 2006
# International Diabetes Federation Clinical Guidelines Taskforce: Global Guideline for Type 2 Diabetes. Brussels, International Diabetes Federation, 2005
# McPherson R, Frohlich J, Fodor G, Genest J, the Canadian Cardiovascular Society: Canadian Cardiovascular Society position statement: recommendations for the diagnosis and treatment of dyslipidemia and prevention of cardiovascular disease. Can J Cardiol 22:913–927, 2006[Medline]
# Feldman RD, Campbell N, Larochelle P, Bolli P, Burgess ED, Carruthers SG, Floras JS, Haynes RB, Honos G, Leenen FH, Leiter LA, Logan AG, Myers MG, Spence JD, Zarnke KB: 1999 Canadian recommendations for the management of hypertension. CMAJ 161 (Suppl.):S1–S17, 1999[Medline]
# Hux JE, Ivis F, Flintoft V, Bica A: Diabetes in Ontario: determination of prevalence and incidence using a validated administrative data algorithm. Diabetes Care 25:512–516, 2002[Abstract/Free Full Text]
# Austin PC, Daly PA, Tu JV: A multicenter study of the coding accuracy of hospital discharge administrative data for patients admitted to cardiac care units in Ontario. Am Heart J 144:290–296, 2002[CrossRef][Medline]
# Petersen LA, Wright S, Normand SL, Daley J: Positive predictive value of the diagnosis of acute myocardial infarction in an administrative database. J Gen Intern Med 14:555–558, 1999[CrossRef][Medline]
# Jackevicius CA, Mamdani M, Tu JV: Adherence with statin therapy in elderly patients with and without acute coronary syndromes. JAMA 288:462–467, 2002[Abstract/Free Full Text]
# Wolff AM, Taylor SA, McCabe JF: Using checklists and reminders in clinical pathways to improve hospital inpatient care. Med J Aust 181:428–431, 2004[Medline]
# Biviano AB, Rabbani LE, Paultre F, Hurley E, Sullivan J, Giglio J, Mosca L: Usefulness of an acute coronary syndrome pathway to improve adherence to secondary prevention guidelines. Am J Cariol 91:1248–1250, 2003
# Brown LC, Johnson JA, Majumdar SR, Tsuyuki RT, McAlister FA: Evidence of suboptimal management of cardiovascular risk in patients with type 2 diabetes mellitus and symptomatic atherosclerosis. CMAJ 171:1189–1192, 2004[Abstract/Free Full Text]
# Elad Y, French WJ, Shavelle DM, Parsons LS, Sada MJ, Every NR: Primary angioplasty and selection bias in patients presenting late (>12 h) after onset of chest pain and ST elevation myocardial infarction. J Am Coll Cardiol 39:826–833, 2002[Abstract/Free Full Text]
# Krumholz HM, Radford MJ, Ellerbeck EF, Hennen J, Meehan TP, Petrillo M, Wang Y, Jencks SF: Aspirin for secondary prevention after acute myocardial infarction in the elderly: prescribed use and outcomes. Ann Intern Med 124:292–298, 1996[Abstract/Free Full Text]
# Ko DT, Mamdani M, Alter DA: Lipid-lowering therapy with statins in high-risk elderly patients: the treatment-risk paradox. JAMA 291:1864–1870, 2004[Abstract/Free Full Text]
# Rasmussen JN, Gislason GH, Abildstrom SZ, Rasmussen S, Gustafsson I, Buch P, Friberg J, Kober L, Torp-Pedersen C, Madsen M, Stender S: Statin use after acute myocardial infarction: a nationwide study in Denmark. Br J Clin Pharmacol 60:150–158, 2005[CrossRef][Medline]
# Stone PH, Thompson B, Anderson HV, Kronenberg MW, Gibson RS, Rogers WJ, Diver DJ, Theroux P, Warnica JW, Nasmith JB, Kells C, Kleiman N, McCabe CH, Schactman M, Knatterud GL, Braunwald E: Influence of race, sex, and age on management of unstable angina and non-Q-wave myocardial infarction: the TIMI III registry. JAMA 275:1104–1112, 1996[Abstract]
# Krumholz HM, Murillo JE, Chen J, Vaccarino V, Radford MJ, Ellerbeck EF, Wang Y: Thrombolytic therapy for eligible elderly patients with acute myocardial infarction. JAMA 277:1683–1688, 1997[Abstract]
# Ramsay SE, Morris RW, Papacosta O, Lennon LT, Thomas MC, Whincup PH: Secondary prevention of coronary heart disease in older British men: extent of inequalities before and after implementation of the National Service Framework. J Public Health (Oxf) 27:338–343, 2005

Diabetes Care 30:381-383, 2007
DOI: 10.2337/dc06-1654
© 2007 by the American Diabetes Association