Author + information
- Received April 23, 2002
- Revision received November 7, 2002
- Accepted January 9, 2003
- Published online May 7, 2003.
- ↵*Reprint requests and correspondence:
Dr. Kwame O. Akosah, Gundersen Lutheran Medical Foundation, 1836 South Avenue, La Crosse, Wisconsin 54601, USA.
Objectives The purpose of this study was to investigate the utility of the new National Cholesterol Education Program (NCEP) III guidelines in a group of young adults.
Background These guidelines have been hailed as an improvement in their potential to identify individuals at risk for coronary heart disease (CHD) complications. Compared with the NCEP II, the new guidelines will increase the number of patients who qualify for medical management. However, the effectiveness of these guidelines to identify young adults at risk for a cardiac event is yet to be studied.
Methods A retrospective review of clinical data from young adults (age ≤55 years for men and ≤65 years for women) hospitalized for acute myocardial infarction over a three-year period was conducted. Patients with a history of CHD or CHD equivalent were excluded. Using the NCEP III guidelines, we calculated a 10-year risk for coronary events on all patients.
Results A total of 222 patients met criteria for inclusion. The mean age was 50 years and 25% were women. Mean lipid levels were all within the normal range; however, rates of smoking and obesity were high. When the 10-year risk of these patients was stratified by the number of risk factors and low-density lipoprotein cholesterol level, only 25% met criteria to qualify for pharmacotherapy. For women in this population, only 18% met criteria for treatment.
Conclusions The new guidelines offer multiple new features but have a tendency to underappreciate the risk for disease in young adults. To improve performance in young adults, statistical adjustments may be necessary.
During the past four decades there has been a slow but steady decline in age-adjusted mortality rates following acute myocardial infarction (MI) (1). This improvement to a large extent is attributed to newer treatment modalities for acute-phase MI such as reperfusion strategies (2,3)and secondary prevention strategies including beta-blockers (4,5), aspirin (6), statins (7,8), and lifestyle changes (9,10). However, the incident rate of acute coronary syndrome per se has not slowed (1). Furthermore, primary prevention of acute MI in the first place has been frustrating.
Today, the cornerstone of primary prevention of coronary heart disease (CHD) in the U.S. is cholesterol management. The National Cholesterol Education Program (NCEP) was established as a national effort to educate professionals and the public on the importance of cholesterol abnormalities and CHD (11). The NCEP has created guidelines for primary and secondary prevention of CHD. These guidelines are derived from evidence-based practice, supported by several trials that demonstrate how treatment of high cholesterol following acute MI improves outcomes (12,13). Similarly, large trials have shown the benefits of prophylactic treatment for primary prevention in certain high-risk groups (14–16).
Recently, updated NCEP guidelines (17)were published that include several new features designed to reclassify risk based on the probability of an event in 10 years. In addition, criteria were set for specific groups in the population, such as for people with diabetes mellitus and others with noncoronary manifestations of atherosclerotic disease. However, this new document has not been tested across different population groups.
Previously we published a paper in which we found that the NCEP II guidelines underestimated disease risk in young adults (18). The purpose of this study was to investigate the utility of the new NCEP III guidelines in a group of young adults.
This is a retrospective study of young adults presenting with MI who were admitted to the Coronary Care Unit at the Gundersen Lutheran Medical Center in La Crosse, Wisconsin, with an MI in a three-year period (January 1, 1998, to December 31, 2000). The hospital catchment area and the demographic profile of the community have been previously published (18). Age criteria for young adults were defined as men age ≤55 years and women age ≤65 years. Acute MI was defined as two of the following: angina, electrocardiographic changes, or elevated enzyme levels (creatine kinase, creatine kinase-myocardial band isoenzyme). Patients were excluded if they had a history of CHD or diabetes (a CHD risk equivalent).
Data source and variables
Medical records of all eligible patients were reviewed. The presence of traditional cardiovascular risk factors was noted. Body mass index (BMI) was calculated for all patients and expressed as weight in kilograms divided by the square of height in meters (kg/m2). Overweight was defined as BMI 25 to 30 kg/m2and obesity was defined as BMI >30 kg/m2for both men and women. Cigarette smoking (yes or no) was ascertained for current use, which was defined as chronic cigarette smoking up to four weeks before acute MI. History of smoking was established if the person reported smoking cessation for longer than four weeks before the event. History of hypertension was defined as systolic blood pressure ≥140 mm Hg or diastolic pressure of ≥90 mm Hg or current use of antihypertensive medication. Family history of premature CHD was defined as CHD in a first-degree relative at age ≤55 years and ≤65 years for men and women, respectively. Hospital discharge records confirmed documentation of MI. Per our clinical care pathway, all patients with acute coronary syndrome have a lipid profile drawn within 12 h of admission. If the patient has eaten in the past 12 h, the patient receives nothing by mouth and a lipid profile is drawn 12 h from the last meal.
Using the modified Framingham risk predictor model as published in the new NCEP guidelines, we calculated a 10-year risk for coronary events on all patients. This was done to see how well we would have identified these young adults for prophylactic pharmacotherapy before their event.
The data were analyzed with SPSS software (Version 9.0 for Windows, SPSS Inc., Chicago, Illinois). Frequency distributions are reported and the Student ttest was used to determine differences between genders.
In the calendar years 1998 through 2000, there were a total of 284 admissions of young adults for acute MI to our hospital. According to the new NCEP guidelines, 62 (18%) would have been classified as having CHD or a CHD equivalent before their MI. The remaining 222 comprised the population used in this study. Demographics are provided in Table 1. The mean patient age was 50 ± 7 years. There were 56 women (25%).
Table 1provides a summary of the details of the traditional risk factor distribution in this population. The mean BMI was 30.0 ± 5.8 kg/m2. Obesity was present in 45% of the patients and an additional 37% were overweight. Thus, overweight and obese patients comprise 82% of this population. Similarly, a history of smoking was high and accounted for 75% of the population. As many as 60% of patients were current smokers. As can be appreciated from Table 1, the frequency rate for each categorical variable was high. Under the new guidelines, major risk factors include: smoking, hypertension, low high-density lipoprotein (HDL) cholesterol (<40 mg/dl), family history of CHD (CHD in male first-degree relative <55 years, in female first-degree relative <65 years), and age (men ≥45 years, women ≥55 years). In our population, multiple major risk factors were present in 109 (49%) patients, whereas 113 (51%) had either no or only one risk factor.
Table 2displays the mean values of the lipoprotein analysis. All 222 young adults had lipid profiles drawn within 12 h of admission. As can be appreciated the mean total cholesterol (190 mg/dl), low-density lipoprotein (LDL) cholesterol (126 mg/dl), and HDL cholesterol (43 mg/dl) were all within the normal range. As a group, only 16% (n = 32) had LDL cholesterol 160 mg/dl or higher. The proportion of patients with LDL cholesterol <130 mg/dl was 58%, of whom 40% (n = 51) of patients had LDL cholesterol <100 mg/dl.
10-year calculated risk
The 10-year CHD risk in these patients was stratified according to the number of major risk factors present and LDL cholesterol level. The number of people at high risk, that is, a 10-year risk >20% and two or more major risk factors, was 27 (12%), of whom only half qualified for pharmacotherapy. Similarly, among the 39 patients with moderate risk (10% to 20%), only 21 qualified for pharmacotherapy. In contrast, among low-risk groups, very few qualified for therapy (6% of people with a 10-year risk <10%, and 16% of people with no or one risk factor). Remarkably, the majority (70%) of young adults were stratified into these two lowest risk categories (n = 156). Table 3provides a more complete illustration of the 10-year calculated risk data. Overall, 166 patients (74.7%) did not meet criteria to be identified as at sufficient risk to qualify for pharmacotherapy. We repeated the analysis using non-HDL cholesterol but the results did not change.
There were 56 (25%) women in this study population. A comparison between genders for lipid values was determined using the Student ttest. The mean total cholesterol was the same in both genders (190 ± 44 mg/dl and 190 ± 43 mg/dl in women and men, respectively). The mean HDL cholesterol level was 46 ± 14 mg/dl for women and 42 ± 15 mg/dl for men and not statistically different (p > 0.5). Women had a statistically lower mean LDL cholesterol level (117 ± 40 mg/dl vs. 129 ± 38 mg/dl, p = 0.014). In contrast, the mean triglyceride level was significantly higher in women than men (160 ± 76 mg/dl vs. 140 ± 77 mg/dl, p = 0.043). Whereas 35 men (21%) had no known traditional cardiovascular risk factors, all of the women had at least one risk factor, excluding high HDL cholesterol. Counting high HDL cholesterol as a negative risk factor, four women qualified as having no risk factors. Also, using the Student ttest, the mean number of major risk factors present was higher in women than men (2.9 vs. 1.5 risk factors, p < 0.001). In spite of the higher mean number of risk factors present, no woman in this study had a calculated risk of >20%. Only 5% of women in this study had risk scores for probability of 10-year event between 10% and 20%. Thus, the majority of women had a 10-year risk of <10%. Overall, 82% of women did not score high enough to be identified for pharmacotherapy by the new guidelines, compared with 59% of men.
Although mortality from CAD has declined steadily in the past four decades, rates for acute coronary syndrome have not slowed. Preventing the development of CHD and initial MIs in the first place has been difficult. The new NCEP III guidelines (17)for the management of dyslipidemia is the best available document for primary prevention. This document has several new features that make it an improvement over previous guidelines. For primary prevention, physicians are encouraged to calculate an individual’s absolute risk for a cardiac event in 10 years. The LDL cholesterol targets and goals of treatment are stratified according to the absolute risk. A major advantage of the new guidelines is that many people who did not qualify for aggressive medical management using previous guidelines will be offered pharmacotherapy (19,20). However, the utility of these new guidelines has yet to be tested, particularly among young adults, a population in which limitations of the previous guideline have been recently documented (18,21).
In this study we applied the new guidelines in a group of 284 young adults with known acute MI. Our goal was to determine each individual’s level of risk and whether or not they would have met criteria for medical management if they had presented to their physicians before the event. Of the entire cohort, only 62 people (22%) had known CHD or CHD equivalent and were excluded from this analysis because they qualified for secondary prevention. The remaining 222 would have been candidates for primary prevention if they had presented to their physicians before the MI. As many as 75% did not qualify for medical management. The prediction model as shown in Table 3is better for moderate- to high-risk patients, identifying 52% of the people in this category. However, only 16% of the entire cohort was in that group.
The infarct these patients had proved they were at high risk. It seems reasonable to expect a predictive model to detect more of these patients than it did. What are some of the reasons that these guidelines do not perform well in young adults? We did not study possible mechanistic reasons, but do offer the following speculations. One reason is that young adults have rarely been studied. With the exception of a few studies such as Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPs/TexCAPs) (14), young adults have been poorly represented in large multicenter trials. Second, the clinical profile of young adults with MI may be different from what is traditionally believed (19,21). Premature CHD was considered rare unless certain conditions, such as cocaine abuse, familial hyperlipidemia, or diabetes were present. In our experience, 25% of all acute coronary syndrome hospital admissions were in adults 50 years or younger (18). Moreover, this young adult population with CHD is characterized by a high prevalence of individual categorical risk factors, but as many as 50% do not have clusters (two or more) of risk factors. Moreover, a significant number of these young adults have LDL cholesterol below 100 mg/dl (22).
As can be viewed in Table 1, the frequency rate of smoking is exceptionally high. In the new guidelines, smoking is stratified according to age with higher scores assigned to younger ages. For instance, a 20- to 29-year-old smoker is assigned a score of 8, whereas a 50- to 59-year-old smoker is given a score of 3. This system of scoring fails to account for the intensity of exposure (duration and number of packs) to tobacco. In the risk assessment of young adults, the intensity of smoking (defined as number of pack years) may be a better basis for stratification than age.
In addition, overweight/obesity as a traditional risk factor was present in 82% of these young adults. In the new guidelines, obesity is not directly scored in risk assessment. The effect of obesity may be accounted for in the role it plays in metabolic syndrome and hypercholesterolemia. However, in a population such as our subjects with high frequency rates of overweight, the full impact of obesity may be unappreciated. The effect of obesity on CHD may need to be re-evaluated in the current era where obesity rates are increasing in all segments of the population.
It may be that (for young adults) long and intense exposure to certain major categorical risk factors may be more detrimental than exposure to multiple marginal risk factors. This may be true for risk factors such as smoking and obesity, both of which are usually acquired early and have a high probability of being maintained.
A distinguishing feature in the clinical profile of our adults is that the vast majority did not have high total cholesterol or LDL cholesterol levels. As many as 58% had LDL cholesterol levels of 130 mg/dl or less, and 50% do not have multiple risk factors. These factors may contribute to the poor performance of current guidelines for prevention of premature CHD.
Does this mean that cholesterol is not important in young adults? We interpret our results to mean that optimal cholesterol levels do not imply freedom from CHD in young adults with other modifiable risk factors. The message is that we should target all modifiable risk factors with the same intensity given to cholesterol.
The Adult Treatment Panel III guidelines incorporate several new features that may potentially improve primary prevention of premature CHD. However, for physicians to feel comfortable with these, they may need to be validated across several population groups. We found that many young adults presenting with MI do not have multiple risk factors, and few (16%) have moderately high LDL cholesterol levels. By contrast, the rates of categorical risk factors including overweight/obesity, smoking, and hypertension are high. Young women presenting with MI generally have a higher likelihood of multiple risk factors. In spite of this, the new guidelines failed to appreciate the risk for underlying disease in women. More studies are needed to validate the new guidelines in young adults and to determine the necessary statistical adjustments to improve performance in young adults at risk for MI.
☆ Funding was provided by the Gundersen Lutheran Medical Foundation, La Crosse, Wisconsin.
- body mass index
- coronary heart disease
- high-density lipoprotein
- low-density lipoprotein
- myocardial infarction
- National Cholesterol Education Program
- Received April 23, 2002.
- Revision received November 7, 2002.
- Accepted January 9, 2003.
- American College of Cardiology Foundation
- American Heart Association
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