|
Ann is a 46-year old executive who just got off the
phone with her physician. The results of the blood tests from her physical
examination are in and by this time tomorrow, she will be on a low-fat diet
and taking a prescription drug to lower her blood cholesterol levels to a
safe range.
Table 1 shows that both her total cholesterol
and LDL-cholesterol (the "bad' cholesterol) are abnormally high. And
although her HDL-cholesterol (the "good" cholesterol is within the desirable
range, the relationship (or ratio) between the total cholesterol blood
concentration and HDL-cholesterol is also too high.
Table 1. Lipid profile for Ann with desirable and high
values
|
|
Result
|
Desirable
|
Abnormal
|
|
Total cholesterol
(mg/dL)
|
302 |
Less than 200 |
Greater than 240 |
|
LDL-cholesterol
(mg/dL)
|
228 |
Less than 130 |
Greater than 160 |
|
HDL-cholesterol
(mg/dL)
|
60 |
Greater than 35 |
Less than 35 |
|
Cholesterol/HDL
ratio |
5.5 |
Less than 4.45 |
- |
Ann is willing to start treatment, but now that she has
had time to think about it, she has lots of questions. As she lights
another cigarette she asks, "Why am I at risk for coronary artery
disease? What is a risk factor, anyway? What do the cholesterol results
really mean? Why didn't my doctor just change my diet? I could try going off
fat for about 6 months and then be tested again. Isn't there any
complementary or alternative treatment that might be safer and still get my
cholesterol into the normal range?
Ann's risk factors
The fact is that her lipid levels are significantly
abnormal. Ann is among more than 60 million Americans at risk of coronary
heart disease. All heart attacks, with rare exceptions, are caused by
atherosclerosis, which is a narrowing and "hardening" of the blood vessels
that bring oxygen-carrying blood to the heart. The narrowing occurs because
of an imbalance between LDL-cholesterol, which deposits fatty plaque on the
vessel walls and HDL-cholesterol, which removes the fatty deposits and
brings them to the liver for metabolism.
Furthermore, Ann is a smoker, with high blood pressure
(systolic blood pressure = 130 mmHg): two more risk factors for heart
disease. The roundtrip commute to her Manhattan office takes at least 3
hours each day. Yes, her career is exciting and she loves it, but it is
stressful and consumes most of her waking hours. Consequently, she has
little time and energy when she finally gets back to her condo in New Jersey
at the end of the day. She spends little time exercising and the "power"
lunches and dinners with clients have lead to weight gain. She has gained
about 25 pounds since college. Constant stress, lack of exercise and obesity
are additional risk factors for Ann.
Who decides what is a risk factor?
Ann has lots of risk factors. But what, exactly, is a
risk factor, and how do laboratory values or physical characteristics become
recognized as a "risk factor" for coronary heart disease?
The term "risk factor" was originally coined by Dr.
William Kannel, the first director of the famous Framingham study. In 1948,
researchers in the Boston suburb of Framingham, Massachusetts enrolled more
than 5,000 local residents and monitored them and their offspring for
decades. It became clear that certain factors predisposed a person to the
development of atherosclerosis (hardening of the arteries). The work from
Framingham, as well as from other studies, resulted in the creation of a
list of risk factors.
This list is not static. The consensus over what is a
risk factor changes as more information becomes available. Risk factors are
also not absolute predictors of coronary artery disease. Heart attacks occur
in people without risk factors, while many people with risk factors never
experience heart disease. However, the likelihood of heart disease is higher
among those with risk factors. And the risk increases with each additional
risk factor a person has. Table 2 lists factors generally thought to
increase the risk of cardiovascular disease.
Table 2. Cardiovascular risk factors
|
·
Age
·
Behavioral factors (eg,
stress, Type A)
·
Cigarette smoking
·
Cocaine
·
Diabetes
·
Elevated serum cholesterol
·
Fibrinogen
·
Gender
·
Glucose intolerance
·
Heredity
·
High blood pressure
·
Left ventricular
hypertrophy
·
Lipoprotein (a)
·
Obesity
|
Criteria
for a risk factor
A laboratory value or physical characteristic becomes a
risk factor for coronary heart disease, when it meets certain criteria.
These include the following.
·
A strong statistical association between the factor and
cardiovascular disease
·
A consistent association that the risk factor produces disease
regardless of sex, age or race
·
The association must make biological sense
·
Treatment should favorably change the risk factor
·
The factor should make an independent contribution to
increasing the person's risk of developing disease.
It is also desirable, but not essential, that the
impact of the risk factor be demonstrated in the laboratory studies.
Calculating risk
It is possible to compare Ann's risk of developing
heart disease over the next decade to the others in her community by using
Tables 3 and 4, which are based on the Framingham Heart Study.
The formula is simple: age + HDL-cholesterol + total
cholesterol + systolic blood pressure + smoking + diabetes + EKG evidence of
an enlarged left ventricle in the heart provide a point score. This value is
compared to others in another table (Table 3) to determine the comparative
risk of having coronary artery disease.
Table 3. Coronary heart disease risk
factor prediction chart: Framingham Heart Study
|
Women |
Men |
Cholesterol |
Systolic
Blood Pressure |
|
Age |
Pts |
Age |
Pts |
HDL |
Pts |
Total |
Pts |
SBP |
Pts. |
|
30
31
32
33
34
35
36
37
38
39
40
41
42-43
44
45-46
47-48
49-50
5152
53-55
5660
61-67
6874 |
-12
-11
-9
-8
-6
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11 |
0
31
32-33
34
35-36
37-38
39
40-41
42-43
44-45
46-47
48-49
50-51
52-54
5556
57-59
60-61
62-64
65-67
68-70
7173
74 |
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19 |
25-26
27-29
30-32
33-35
36-38
39-42
43-46
47-50
51-55
56-60
61-66
67-73
74-80
81-87
88-96
|
7
6
5
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
|
139-151
152-166
167-182
183-199
200-219
220-239
240-262
263-288
289-315
316-330 |
3
2
1
0
1
2
3
4
5
6
|
98-104
105-112
113-120
121-129
130-139
140-149
150-160
161-172
173-185 |
-2
-1
0
1
2
3
4
5
6 |
Cigarette smoker: add 4 points (Pts)
Diabetic male: add 3
points
Diabetic female: add 6
points
EKG evidence of left
ventricular hypertrophy: add 9 points
Source: Black, 1992.
Table 4. Probability of coronary
heart disease and comparative 10-year risk
|
Probability of CHD |
Average 10-Year Risk |
|
Pts |
5 Yr |
10 Yr |
Pts |
5 Yr |
10 Yr |
Age |
Women |
Men
|
|
<1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
|
<1%
1%
1%
1%
1%
1%
1%
2%
2%
2%
3%
3%
3%
4%
5%
5%
|
<2%
2%
2%
2%
3%
3%
4%
4%
5%
6%
6%
7%
8%
9%
10%
12%
|
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32 |
6%
7%
8%
8%
9%
11%
12%
13%
14%
16%
17%
19%
20%
22%
24%
25% |
13%
14%
16%
18%
19%
21%
23%
25%
27%
29%
31%
33%
36%
38%
40%
42% |
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
70-74 |
<1%
<1%
2%
5%
8%
12%
13%
9%
12% |
3%
5%
6%
10%
14%
16%
21%
30%
24% |
Source: Black, 1992.
Ann gets 4 points for her age, 46 years. Her HDL-cholesterol
is in the desirable range (subtract 2 points = 2 points). However, total
cholesterol is high, primarily due to her elevated LDL-cholesterol (add 5
points = 7). With a systolic blood pressure of 130 mmHg she adds another 2
points plus 4 more for being a smoker (add 6 points = 13).
Her total is 13, which translates in Table 4 to a 3%
risk for coronary heart disease in the next 5 years and 8% in the next 10
years. By comparison, the average 10-year risk for women her age is 5%.
Therefore, Ann's current physical condition and lifestyle include factors
that increase by 3% her risk of being diagnosed with coronary heart disease
by the time she is 56 years old.
A complementary strategy for controlling risk
The key to reducing risk is to control the factors that
predispose to heart disease. The first step is to stop smoking. According to
the Framingham tables, this change alone in her lifestyle will lower her
risk to within the average range for women her age.
Next comes diet. For many people with borderline high
cholesterol, dietary changes may be sufficient to lower cholesterol into the
desirable range. Unfortunately for Ann, her LDL-cholesterol and total
cholesterol are so high, she will probably have to combine diet with drug
therapy.
It's worth the effort
Stopping smoking could add 7 years to her life,
according to the Centers for Disease Control and Prevention. Lowering
cholesterol will also reduce her chances of developing coronary heart
disease and suffering the other complications associated with heart disease,
such as myocardial infarction and coronary artery bypass grafting.
Acting now could make the difference in being here to
see her daughter graduate from college, or hold her first grandchild, or
enjoy a few years of quality retirement after 2 or 3 decades of 3-hour
roundtrip commutes to work. It's worth the effort.
Dr. Russo is vice president of medical communications at
Vicus.com. He is a pharmacist and medical writer, with more than 20 years of
experience in medical education.
References
Holme I. Effects of lipid-lowering
therapy on total and coronary mortality. Curr Opin Lipidol, 1995;
6(6):374-8.
Le Fur C. Influence of mental stress and
circadian cycle on postprandial lipemia. Am J Clin Nutrition, 1999;
70:213-20.
Black, HR. Cardiovascular risk factors.
Chapter 3. In, Yale University School of Medicine Heart Book. Zaret BL,
Moser M, Cohen LS [eds]. New York, Hearst Books, 1992.
Centers for Disease Control and
Prevention. Smoking-attributable mortality and years of potential life
lostUnited States, 1990. Morbidity and Mortality Weekly Report 1993;
42(33):645-8.
Centers for Disease Control and
Prevention. Office on Smoking and Health, unpublished data, 1994. |
