EAL

DM: Prevention and Treatment of CVD (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine the effect of diabetes on long-term survival after acute myocardial infarction to compare its effect with that of a previous myocardial infarction.

Inclusion Criteria:

1. CK-MB isoenzyme level above the upper limit of normal for each medical center.

2. Identifiable onset of symptoms of infarction

3. Able to complete a structured interview.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment: The Onset Study was conducted in 45 medical centers in the US. Trained research interviewers identified eligible subjects by reviewing coronary care unit admission logs and patient charts

Design: Between August 1989 and September 1994, 1,935 patients (601 women and 1,334 men) hospitalized after sustaining an acute myocardial infarction (AMI) were interviewed a median of 4 days after the AMI.

Blinding Used (if applicable):

Not applicable.

Intervention (if applicable):

Patient interview.

Statistical Analysis: Analysis of survival using Cox proportional hazards regression to control for potentially confounding factors.

Data Collection Summary:

Timing of Measurements: patients were interviewed a median of 4 days after sustaining an AMI. National death records were searched through December 31, 1995.

Dependent Variable

Death: National Death Index used to search for deaths of subjects in the Onset Study through December 31, 1995 and requested death certificates from state offices of vital records.
Structured data collection/abstraction form to obtain the following data: age, sex, medical history, medication use, complications from CHF or ventricular tachycardia.

Independent Variable

diabetes: history of diabetes from medical record or current use of any hypoglycemic medication; type of diabetes and duration of diabetes prior to AMI was recorded when available.
aspirin use: use of aspirin or any aspirin-containing product 4 days prior to AMI.

Control Variables

age
sex
previous MI, angina, or hypertension
medication use before hospitalization
current smoking
previous smoking
BMI
thrombolytic therapy
usual frequency of exertion
alcohol consumption
household income
education
complications of CHF or ventricular tachycardia during hospitalization

Description of Actual Data Sample:

Initial N: 1935 patients interviewed. A total of 399 patients (21%) had previously diagnosed diabetes.

Attrition (Final N): See above.

Age, Ethnicity, Other Relevant Demographics, and Anthropometrics

The sample with diabetes had these characteristics:

average age of 65 ± 11 years
41% female
87%white
BMI 27.6 ± 5.7
21% were current smokers
39% had hx of previous MI
62% had hypertension

Patients with diabetes were significantly older, and the sample had more females, fewer whites, higher BMIs, fewer current smokers, more previous MIs, more angina, and more hypertension than those with no history of diabetets.

Location: Boston, MA

Summary of Results:

Other Findings:

Of the 1,935 patients, 320 (17%) died during a mean follow-up period of 3.7 yr. Of the diabetic patients, 29% died.

Diabetes was associated with a markedly higher total mortality in unadjusted (hazard ratio 2.4; 95% CI, 1.9 to 3.0 and adjusted (1.7; 1.3 to 2.1) analyses.

The magnitude of the effect of diabetes was identical to that of a previous MI.

The effect of diabetes was not significantly modified by age, smoking, household income, use of thrombolytic therapy, type of hypoglycemic treatment, or duration of diabetes, but the risk associated with diabetes was higher among women than men (adjusted hazard ratio, 2.7 vs. 1.3, P=0.01).

Author Conclusion:

Diabetes is associated with markedly increased mortality after acute MI particularly in women. The increase in risk is of the same magnitude as a previous MI and provides further support for aggressive treatment of coronary risk factors among those with diabetes.

A limitation of this study is the lack of information regarding secondary prevention strategies used to treat the subjects. Also, this study was conducted before studies confirmed that intensive blood glucose control lowers the risk of AMI and decreases mortality during and after AMI among patients with diabetes.

More research is needed on specialized primary and secondary prevention strategies for those with diabetes.

Funding Source:

Government:

NIH

Reviewer Comments:

This study did not include HbA1c values or any measure of glycemic control, and may have misclassified patients with unrecognized diabetes since diabetes was defined as a history of diabetes or current use of hypoglycemic medications. This study clearly demonstrated an increased risk for death post MI in individuals with diabetes.

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	N/A
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	No
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	N/A

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		???
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	No
	2.2.	Were criteria applied equally to all study groups?	N/A
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
3.	Were study groups comparable?		???
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	???
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	???
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		No
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	No
	6.6.	Were extra or unplanned treatments described?	No
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	???
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	Yes
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes