Download Circulation 2000

Impact of Diabetes on Long-Term Prognosis in Patients
With Unstable Angina and Non–Q-Wave
Myocardial Infarction
Results of the OASIS (Organization to Assess Strategies for Ischemic
Syndromes) Registry
Klas Malmberg, MD, PhD; Salim Yusuf, MBBS, DPhil; Hertzel C. Gerstein, MD, MSc;
Joanne Brown, BSc; Feng Zhao, MSc; David Hunt, MD; Leopoldo Piegas, MD; James Calvin, MD;
Matyas Keltai, MD; Andrzej Budaj, MD; for the OASIS Registry Investigators
Background—Although unstable coronary artery disease is the most common reason for admission to a coronary care unit,
the long-term prognosis of patients with this diagnosis is unknown. This is particularly true for patients with diabetes
mellitus, who are known to have a high morbidity and mortality after an acute myocardial infarction.
Methods and Results—Prospectively collected data from 6 different countries in the Organization to Assess Strategies for
Ischemic Syndromes (OASIS) registry were analyzed to determine the 2-year prognosis of diabetic and nondiabetic
patients who were hospitalized with unstable angina or non–Q-wave myocardial infarction. Overall, 1718 of 8013
registry patients (21%) had diabetes. Diabetic patients had a higher rate of coronary bypass surgery than nondiabetic
patients (23% versus 20%, P⬍0.001) but had similar rates of catheterization and angioplasty. Diabetes independently
predicted mortality (relative risk [RR], 1.57; 95% CI, 1.38 to 1.81; P⬍0.001), as well as cardiovascular death, new
myocardial infarction, stroke, and new congestive heart failure. Moreover, compared with their nondiabetic counterparts, women had a significantly higher risk than men (RR, 1.98; 95% CI, 1.60 to 2.44; and RR, 1.28; 95% CI, 1.06 to
1.56, respectively). Interestingly, diabetic patients without prior cardiovascular disease had the same event rates for all
outcomes as nondiabetic patients with previous vascular disease.
Conclusions—Hospitalization for unstable angina or non–Q-wave myocardial infarction predicts a high 2-year morbidity
and mortality; this is especially evident for patients with diabetes. Diabetic patients with no previous cardiovascular
disease have the same long-term morbidity and mortality as nondiabetic patients with established cardiovascular disease
after hospitalization for unstable coronary artery disease. (Circulation. 2000;102:1014-1019.)
Key Words: diabetes mellitus 䡲 angina 䡲 myocardial infarction 䡲 prognosis
D
iabetes increases the risk of cardiovascular outcomes
and mortality in patients with established cardiovascular
disease (CVD). Patients with diabetes with no history heart
disease have the same risk for future cardiovascular death as
nondiabetic patients with a history of myocardial infarction
(MI).1 Furthermore, patients with diabetes have not experienced the reduction in mortality rates that recently has been
observed in nondiabetic people.2 These observations, plus the
fact that the prevalence of diabetes is likely to double during
the first quarter of the 21st century,3 suggest that the importance of diabetes as a cardiovascular risk factor will increase
substantially.
Several previous studies have shown that patients with
diabetes have higher mortality and morbidity rates than
nondiabetic patients after an acute MI.4 – 6 This increased risk
is also evident after implementation of both modern revascularization and pharmacological treatment strategies.7 Despite
these observations, few studies have assessed the prognosis of
diabetic patients after hospital admission with the most
common reason for admissions to a coronary care unit:
unstable angina and non–Q-wave MI. One case-control study
found that patients with diabetes had higher 3-month and
1-year mortality rates than nondiabetic patients. Furthermore,
patients with diabetes were less likely to have coronary
Received November 29, 1999; revision received February 29, 2000; accepted March 27, 2000.
From the Department of Cardiology, Karolinska Hospital, Stockholm, Sweden (K.M.); the Preventive Cardiology and Therapeutics Program (S.Y., J.B.,
F.Z.) and Division of Endocrinology and Metabolism (H.C.G.), McMaster University, Hamilton, Canada; Royal Melbourne Hospital, Melbourne,
Australia (D.H.); Dante Pazzanese Cardiology Institute, Sao Paulo, Brazil (L.P.); Rush-Presbyterian St. Luke’s Medical Center, Chicago, Ill (J.C.);
Hungary Institute of Cardiology, Budapest, Hungary (M.K.); and Postgraduate Medical School, Grochowski Hospital, Warsaw, Poland (A.B.).
Reprint requests to Professor Salim Yusuf, Preventive Cardiology and Therapeutics, Program, McMaster University, HGH-McMaster Clinic, 237
Barton St E, Hamilton, Ontario L8L 2X2 Canada. E-mail [email protected]
© 2000 American Heart Association, Inc.
Circulation is available at http://www.circulationaha.org
1014
Malmberg et al
angiography and treatment with ␤-blockers.8 Although most
of these studies reported that diabetes predicts a worse
outcome after an episode of unstable coronary artery disease,9,10 conflicting data exist.11 The reason for the conflicting
results probably is that the available studies were small,
involved relatively short follow-up, and were retrospective in
nature.
We therefore compared the outcomes and treatment strategies of patients with and without diabetes mellitus in the
large, prospective Organization to Assess Strategies for
Ischemic Syndromes (OASIS) registry, which provides longterm information on patients with unstable coronary artery
disease from 6 different countries and 95 hospitals.
Methods
A detailed description of methods and patients has been published
elsewhere.12 Briefly, the OASIS registry included patients with acute
ischemic chest pain within 48 hours of onset and suspected unstable
angina or acute MI without initial ST elevation. Ninety-five hospitals
in Australia, Brazil, Canada, the United States, Hungary, and Poland
participated in the study. Each hospital enrolled consecutive eligible
patients during their participation in the study between 1995
and 1996.
Data on clinical variables, procedures, and events were collected
prospectively through the use of standardized forms during hospitalization. If patients were transferred from one hospital to another
for a procedure, these data were also recorded. At 6, 12, and 24
months, data were collected on all interim procedures, occurrence of
MI, rehospitalization for unstable angina, and death. All data were
transmitted to the Canadian Cardiovascular Collaboration Project
office located at the Preventive Cardiology and Therapeutics Research Program at the Hamilton Civic Hospitals Research Center.
Extensive quality-control efforts were made to ensure completeness
and accuracy of data. Data were complete in 99.9% of patients at
hospital discharge, 96.0% at 6 months, 86.0% at 12 months, and
80.3% at 24 months. The protocol was approved by each hospital’s
ethics committee. Informed consent was obtained from each patient.
Definitions
The following prospective definitions were used. Diabetes was
defined as a known history of diabetes mellitus treated with diet or
use of oral glucose-lowering agents or insulin. MI associated with
admission symptoms (onset before hospital admission) was defined
as elevation of cardiac enzymes, eg, creatine kinase (CK) or
diagnostic CK-MB within 12 hours of admission to at least twice the
upper limit of the reference range. To identify new MI occurring
beyond 24 hours after admission, we used 2 of 3 criteria of new onset
of pain, new ECG changes (ST elevation of 2 mm in contiguous
leads, new Q waves, or other persistent ECG changes), or new
enzyme elevations: creatine kinase rise to more than twice the upper
limit of the reference range (or ⬎20% of the previous value of CK
already elevated above the upper limit of the reference range) or a
rise in CK-MB above the reference range. If CK or CK-MB results
were not available, an increase in other less specific cardiac enzymes
as for CK was accepted. Stroke was identified with a clinical
diagnosis (with or without confirmation by CT scan or MRI) with
definite symptoms persisting ⱖ24 hours. Major bleed was defined as
a bleed considered fatal or life-threatening, an overt bleed requiring
transfusion of ⱖ2 units of packed red blood cells (or equivalent), or
a bleed requiring surgical intervention. Heart failure was identified
through a clinical diagnosis of new-onset congestive heart failure
with radiological evidence to support this diagnosis or ejection
fraction measurement ⬍45% (by echocardiography or radionuclide
assessment). A patient was considered to have previous known
cardiovascular disease if previous MI, stroke, congestive heart
failure, PTCA, or CABG had been experienced. The combined end
point was cardiovascular death, new MI, or stroke, whichever
occurred first.
Impact of Diabetes on Unstable CHD
1015
Statistical Analysis
Baseline historical data, in-hospital management, and in-hospital
outcome rates of all diabetic and nondiabetic patients enrolled in the
registry were summarized. Continuous and categorical data were
compared with the use of Student’s t test and Fisher’s exact test,
respectively. Crude relative risks (RRs) and 95% CIs for in-hospital
outcomes in diabetic patients compared with nondiabetic patients
were calculated. To correct for in-hospital treatment dissimilarities,
a logistic regression model was used.
Patients were followed up for 2 years after entering the registry.
Kaplan-Meier event curves for diabetic and nondiabetic patients
were constructed for total mortality, MI occurring after the first 24
hours of hospitalization, stroke, and new onset of congestive heart
failure. Missing 2-year data were treated as censored. These curves
were compared by the log-rank test. Univariate and multivariable
relative hazards and 95% CIs for these outcomes were calculated
with Cox regression models. Variables entered into the multivariable
model included age, sex, diabetes, previous congestive heart failure,
previous MI, previous stroke, previous PTCA, and previous CABG.
To determine the independent prognostic importance of various
clinical factors on the 2-year prognosis after an episode of unstable
angina or non–Q-wave MI, a second Cox regression model was used
in which the above variables and in-hospital use of intravenous
heparin, ␤-blockers, and calcium channel blockers were entered. In
addition, interaction terms for diabetes and sex, heparin, ␤-blockers,
and calcium channel blockers were entered. The only significant
interaction was found in the model for total mortality and was seen
for diabetes and sex. However, entering this interaction term into the
model did not change the other included variables or their relation in
the model. Relative hazards for long-term total mortality is therefore
given from the model not including the interaction term. All
statistical analyses were done with the use of SAS version 6.12.
Results
The study included 8013 patients, of whom 1718 (21%) had
diabetes (Table 1). The prevalence of diabetes varied significantly between different countries, even after correction for
differences in age and sex, with the highest prevalence in the
United States (30%) and the lowest in Australia (16%).
Table 1 gives the baseline characteristics. Diabetic patients
were older and more likely to be female than nondiabetic
patients. They also had significantly more previous cardiovascular events, including MI, congestive heart failure, and
stroke, and more revascularization procedures. Before admission, more diabetic than nondiabetic patients were taking
calcium channel blockers and ACE inhibitors, but prior use of
␤-blockers was the same in both groups.
In-Hospital Treatment and Evaluation
As outlined in Table 1, after admission diabetic patients were
less likely to be treated with ␤-blockers but significantly
more likely to receive calcium channel blockers during their
hospital stay than nondiabetic patients. This was also evident
after correction for dissimilarities between the 2 groups with
regards to age, sex, previous MI, previous stroke, and
previous congestive heart failure in a multivariable logistic
regression analyses. More diabetic patients received ACE
inhibitor treatment than nondiabetics. Approximately three
quarters of all patients received intravenous heparin treatment
with no difference between the 2 groups.
The frequency of cardiac catheterization and in-hospital
rates of PTCA did not differ between diabetic and nondiabetic patients. However, more diabetic patients underwent
CABG surgery.
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Circulation
August 29, 2000
TABLE 1. Baseline Characteristics and Prevalence of Diabetes
in Different Countries
Diabetes
(n⫽1718)
No Diabetes
(n⫽6295)
P
65⫾10
64⫾11
⬍0.001
46
37
⬍0.001
MI
48
41
⬍0.001
Congestive heart failure
18
10
⬍0.001
Stroke
10
4
⬍0.001
PTCA
14
15
0.70
CABG
20
15
⬍0.001
␤-Blockers
33
36
0.36
Calcium channel blockers
51
39
⬍0.001
Antiplatelet drugs
59
53
⬍0.001
ACE inhibitors
36
23
⬍0.001
Parameter
Age, y (mean⫾SD)
Female, %
Previous history, %
Previous treatment, %
In-hospital treatment, %
␤-Blockers
59
65
⬍0.001
Calcium channel blockers
58
52
⬍0.001
Antiplatelet drugs
92
92
0.56
ACE inhibitors
51
34
⬍0.001
Intravenous heparin
72
74
0.34
Angiography
37
37
0.89
PTCA
12
11
0.60
CABG
11
9
0.026
In-hospital evaluation and
revascularization, %
Proportion of diabetes by country, %
Australia
16
Brazil
24
Canada
22
Hungary
22
Poland
20
United States
30
⬍0.001
In-Hospital Morbidity and Mortality
There were no differences between patients with and without
diabetes in the rate of confirmed admission MI, new inhospital MI, or bleeding complications. Patients with diabetes
had a significantly higher crude rate of in-hospital death,
congestive heart failure, and stroke than nondiabetic patients
(Table 2). On average, patients with diabetes stayed 1 day
TABLE 2.
In-Hospital Morbidity and Mortality
Parameter
Admission non–Q-wave MI
Diabetes
(n⫽1718), %
19
19
P
0.86
6
5
0.12
Major bleeding
1
1
0.89
New congestive heart failure
In-hospital death
1.1
12
2.9
Long-Term Outcome
During follow-up, there were no differences in the rates of
coronary angiography and PTCA between patients with or
without diabetes. However, more diabetic patients (23%) than
nondiabetic patients (20%) had CABG during follow-up
(Table 3). Cumulative actuarial event rates for the outcomes
of mortality, new congestive heart failure, reinfarction, and
stroke are given in Figure 1. Patients with diabetes had a
significantly worse long-term outcome in all event categories;
the RR was 1.84 (95% CI, 1.60 to 2.19) for mortality and 1.44
(95% CI, 1.22 to 1.68) for reinfarction. This higher mortality
and morbidity in patients with diabetes was also evident after
adjustment for dissimilarities in baseline variables, including
age, sex, and a previous history of MI, stroke, PTCA, CABG,
and congestive heart failure. Absolute rates and both unadjusted and adjusted hazard ratios (by the Cox model) are
presented in Table 3. The negative impact of diabetes was
consistent for all outcomes across all countries, and there was
no interaction between diabetes and country in a multivariate
analysis (data not shown).
Because patients with diabetes were more likely to have
established CVD at baseline, we also performed stratified
analyses according to prior CVD and reported diabetes status.
Event curves for the stratified analyses are given in Figure 2;
corresponding crude event rates for all outcomes are given in
relation to diabetic status and previous CVD history in Table 4.
A history of diabetes was associated with an increased event rate
for all outcomes for patients both with and without established
CVD. The 2-year mortality rate for diabetic patients was 20.3%
for those with prior CVD compared with 13.0% for those
without prior CVD. For nondiabetic patients, the corresponding
figures were 12.8% and 6.9%, respectively. For all end-point
categories, including the combined end point, the curves for
patients with diabetes and no prior CVD and the curves for
nondiabetic patients with prior CVD were nearly identical
(Figure 2). Indeed, a comparison of event rates for all outcomes
in diabetic patients without prior CVD with nondiabetic patients
with previous CVD in a Cox proportional-hazard model after
adjustment for age and sex did not reveal any differences
between the 2 groups (Table 5). This indicates that after
hospitalization for unstable angina or non–Q-wave MI, a previously healthy patient with diabetes has the same long-term
prognosis as a nondiabetic patient with established CVD. Adjusted RRs between nondiabetic patients without prior CVD and
the other strata are presented in Figure 2.
Prognostic Importance of Clinical Baseline Factors
No Diabetes
(n⫽6295), %
In-hospital reinfarction
Stroke
longer in hospital than nondiabetics (11.4⫾8 versus 10.3⫾8
days, P⬍0.0001).
0.4
⬍0.001
8
⬍0.001
2.0
0.033
To determine the relative impact of clinical baseline factors on
long-term prognosis, the Cox model for mortality was used. In
this model, we also controlled for in-hospital treatment (use of
␤-blockade, calcium channel blockade, and heparin; Table 6).
The most powerful independent predictors were age (RR⫽1.58;
95% CI, 1.48 to 1.69, per 10 years), previous heart failure
(RR⫽2.34; 95% CI, 2.01 to 2.73), and diabetes (RR⫽1.56; 95%
CI, 1.35 to 1.79). Indeed, the fact that the RRs for 10 years of age
and diabetes are almost identical suggests that the risk associated
Malmberg et al
Impact of Diabetes on Unstable CHD
1017
TABLE 3. Crude Event Rates and RRs for Long-Term Outcomes, Including
Invasive Procedures
Crude Event Rate, %
Diabetes
No Diabetes
Unadjusted RR
(95% CI)
P
Adjusted RR
(95% CI)
P
Total mortality
18
10
1.84 (1.60–2.11)
⬍0.001
1.57 (1.38–1.81)
⬍0.001
CVD death
14
8
1.80 (1.54–2.09)
⬍0.001
1.49 (1.27–1.74)
⬍0.001
New MI
12
9
1.43 (1.22–1.68)
⬍0.001
1.34 (1.14–1.57)
⬍0.001
Parameter
5
3
1.68 (1.27–2.22)
⬍0.001
1.45 (1.09–1.92)
0.009
Composite outcome
25
17
1.56 (1.39–1.74)
⬍0.001
1.34 (1.22–1.54)
⬍0.001
New CHF
21
12
1.82 (1.60–2.06)
⬍0.001
1.41 (1.24–1.60)
⬍0.001
Coronary angiography
50
52
0.95 (0.88–1.02)
0.16
1.05 (0.97–1.13)
0.20
Stroke
PTCA
18
18
0.99 (0.87–1.12)
0.87
1.10 (0.97–1.25)
0.15
CABG
23
20
1.19 (1.06–1.33)
0.002
1.33 (1.19–1.49)
⬍0.001
CHF indicates congestive heart failure. RRs are adjusted for baseline dissimilarities in age, sex, and previous history
(stroke, MI, PTCA, CABG, and congestive heart failure) by the Cox proportional hazard model.
with diabetes is similar to the risk of a nondiabetic patient who
is 10 years older. Previous treatment with PTCA was associated
with increased survival (RR⫽0.68; 95% CI, 0.55 to 0.85;
P⬍0.001), whereas previous CABG had a neutral effect (NS;
P⫽0.27).
Prior MI, stroke, and male sex were also independently
associated with long-term mortality. There was a positive
interaction between diabetes and sex (P⫽0.002 for interaction). Diabetes increased the risk for men by 1.28 (95% CI,
1.06 to 1.56). In contrast, the risk was increased by 1.98 (95%
Figure 1. Cumulative event curves for different outcomes in
patients with and without diabetes. RRs and CIs are given by
univariate Cox regression analysis.
CI, 1.60 to 2.44) among women (P⬍0.01 for the differences
between the 2 RRs). Thus, diabetes was of greater prognostic
importance for women than for men.
Discussion
There are 4 major findings of this study. First, the 2-year
morbidity and mortality rates after an acute episode of
Figure 2. Cumulative event curves for patients with and without
diabetes in relation to previously known CVD. Age- and sexadjusted RRs (by Cox model) between nondiabetic patients
without prior cardiovascular disease [(No Diabetes/CVD(⫺)] and
other strata are given. CVD(⫹) indicates prior CVD; CVD(⫺), no
prior CVD.
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Circulation
August 29, 2000
TABLE 4. Crude Event Rates for All Outcomes During 2-Year
Follow-Up in Relation to Diabetic Status and Previous History
of CVD
Previous CVD, %
Parameter
Diabetes
(n⫽1148)
No Diabetes
(n⫽3503)
No Previous CVD, %
Diabetes
(n⫽569)
No Diabetes
(n⫽2796)
Mortality
20.3
12.8*
13.0
6.9*
CVD death
16.6
10.5*
9.3
5.1*
New MI
13.1
10.2†
10.7
7.5†
Stroke
5.1
3.2†
3.0
2.01
Combined end point
27.3
19.9*
19.9
12.9*
New CHF
24.2
16.2*
13.9
7.1*
CHF indicates congestive heart failure. P values are calculated between
patients with and without diabetes within the 2 CVD strata.
*P⬍0.001; †P⬍0.01.
unstable angina or non–Q-wave MI are substantial and
therefore require long-term treatment strategies. Second, the
poor long-term outcome is especially evident among patients
with diabetes mellitus. Third, diabetes per se has the same
impact on future morbidity and mortality as already established cardiovascular disease after a new event. Fourth, the
adverse impact on prognosis of diabetes is greater among
women than men.
Several studies have previously shown that diabetic patients have increased short- and long-term mortality and
morbidity after an acute MI.4 –7 This increase has been
attributed to an increased susceptibility to myocardial pump
failure and reinfarction.4,13,14 In our study, patients with
diabetes had a higher baseline risk factor burden than nondiabetic patients, but even after statistical correction for these
baseline dissimilarities, diabetes turned out to be a major
independent predictor for all event categories. An earlier
study that examined this relationship was a case-control study
that found a 2-fold increased mortality among diabetic
patients compared with nondiabetics during 1 year of follow
up, a difference largely accounted for by an increased early
mortality.8 Another study showed that among patients admitted to hospital with a suspicion of MI, those with a history of
diabetes had a 1-year mortality rate of 25% compared with
10% among nondiabetic patients.15 Our study showed a
TABLE 5. RRs and 95% CIs for Different Outcomes Between
Patients With Diabetes but Without Previous CVD Compared
With Nondiabetic Patients With Prior CVD Adjusted for Age
and Sex
Diabetes but No CVD
RR (95% CI)
P
Mortality
1.16 (0.91–1.49)
0.23
CVD death
1.00 (0.75–1.34)
0.98
New MI
1.18 (0.90–1.55)
0.24
Stroke
0.94 (0.56–1.59)
0.82
Combined end point
1.11 (0.91–1.35)
0.32
New CHF
0.90 (0.71–1.14)
0.38
Parameter
CHF indicates congestive heart failure.
TABLE 6. Independent Impact of Various Clinical Baseline
Factors on Long-Term Total Mortality by Cox
Proportional-Hazards Model With Adjustment for Differences in
In-Hospital Treatment (␤-Blockade, Calcium Channel Blockade,
and Heparin)
Parameter
RR (95% CI)
P
Age (10 y)
1.58 (1.48–1.69)
⬍0.001
Previous congestive heart failure
2.34 (2.01–2.73)
⬍0.001
Diabetes
1.56 (1.35–1.79)
⬍0.001
Previous MI
1.31 (1.15–1.50)
⬍0.001
Previous PTCA
0.68 (0.55–0.85)
⬍0.001
Previous stroke
1.36 (1.09–1.71)
⬍0.01
Sex (female⫽1, male⫽2)
1.18 (1.03–1.35)
⬍0.05
Previous CABG
0.91 (0.76–1.08)
0.265
Included parameters are ordered by their contribution to the model.
progressive increase in mortality and morbidity for patients
both with and without diabetes. Moreover, there was a
continuos widening of the event curves with time, an observation that supports the contention that an episode of unstable
coronary artery disease is a marker of a chronic progressive
disease, which is more advanced and rapidly progressive in
diabetic than in nondiabetic patients. That patients with
diabetes do have accelerated atherothrombotic disease is also
supported by the fact that the diagnosis of diabetes per se had
the same prognostic impact as an increase in age of 10 years.
The finding that patients with diabetes and no previous
CVD experienced the same long-term prognosis as nondiabetic patients with a history of previous CVD is interesting
and supports previous observations of a similar cardiovascular long-term prognosis for diabetic patients without established CVD as for nondiabetic persons who have suffered an
acute MI.1 Our finding confirms this hypothesis in patients
who have suffered an episode of unstable angina or non–Qwave MI. Furthermore, because our result is derived from a
large number of patients from 6 different countries and is very
consistent for all cardiovascular outcomes, it also increases
the generalizability of the concept, thereby reinforcing the
need for meticulous care and modification of risk factors in
patients with diabetes mellitus.
The relatively higher incidence of new congestive heart
failure is consistent with previous studies in postinfarction
patients and may be due to a more vulnerable nonischemic
area, presumably because of vascular reasons or a particular
concomitant diabetes-specific heart disease.16 In addition to
hyperglycemia, diabetes is characterized by an increased
turnover of free fatty acids, which may be one of the
explanations for a diabetes-specific myocardial disease.17
Free fatty acids utilization increases myocardial oxygen
consumption and may enhance intracellular accumulation of
toxic intermediates.18 An encouraging finding was that patients with diabetes received the same care in terms of
invasive evaluation and treatment as nondiabetic patients. In
fact, they had a slightly higher rate of bypass procedures
during follow-up. This presumably reflects a higher prevalence of multivessel disease in patients with diabetes compared with nondiabetic patients who have had previous
Malmberg et al
angiographic studies.14 Earlier reports have found less frequent
use of invasive procedures in patients with diabetes and have
speculated that this may be a reason for a worse prognosis
among diabetics after an unstable coronary event compared with
nondiabetic patients.8 Furthermore, there was no increase in
bleeding complications despite extensive use of both aspirin and
heparin. Previous reports have indicated less use of anticoagulation and thrombolytic treatment among diabetic patients, presumably because of fear of treatment complications.19
We also found an interaction with diabetes and sex with
respect to total mortality. The increased risk among diabetic
woman compared with diabetic men has in several previous
studies been interpreted as evidence that diabetic women have a
worse prognosis than diabetic men.20 However, a more appropriate interpretation is that women with diabetes have the same
poor long-term prognosis as diabetic men and that diabetes
blunts the female protection for cardiovascular disease.
In conclusion, this study demonstrates that diabetes and
unstable coronary artery disease are a common combination. It
also reports that diabetes is an independent risk factor for
long-term morbidity and mortality after an episode of unstable
coronary artery disease even after implementation of modern
evaluation and treatment strategies. The prevalence of diabetes is
expected to increase as the population ages. Therefore, more
knowledge regarding specific care and treatment in this fastgrowing patient population is urgently needed.
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