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3-13 PREVALENCE AND ASSOCIATIONS OF
ABDOMINAL ANEURYSM DETECTED THROUGH SCREENING
Abdominal aortic aneurysm is associated with multiple
factors including age, high cholesterol, hypertension,
and coronary artery disease. In this study, smoking was
the risk factor most strongly associated with AAA and may
be responsible for most clinically important cases of
previously undiagnosed AAA. Annals Int. Med. March 15,
1997; 126:441-49 3-13
PREVALENCE AND ASSOCIATIONS OF ABDOMINAL ANEURYSM
DETECTED THROUGH SCREENING
Aortic aneurysm is the 10th leading cause of death in
older men.
This study identified factors that are independently
associated with abdominal aortic aneurysms (AAA) and
determined the prevalence of previously unrecognized AAA.
Conclusion: AAA is closely linked to smoking.
STUDY
- Cross sectional
screening study in 15 VA medical centers examined
over 73,000 veterans (97% male) ages 50-79. None
had a history of AAA.
- A questionnaire asked
about demographic information and possible risk
factors for AAA.
- Measured the
abdominal aorta above and below the renal
arteries by ultrasound.
- How is AAA defined?
An infrarenal diameter of 4.0 cm of larger is
generally considered to be an aneurysm. These
investigators, in order to avoid the problem of
defining the lower range of diameter, considered
several definitions: 1) Diameter of at least 4.0
cm; 2) Diameter of at least 3.0 cm; and 3) a
ratio of infrarenal to suprarenal aortic diameter
of 1.5 or greater.
RESULTS
1. An AAA of 4.0 cm or
larger was detected in 1,041 participants (1.4%). One in
200 (0.5%) had AAA of 5 cm or larger—a few as high
as 8.0 cm.
2. An AAA defined as 3.0
cm or more was detected in 3 366 subjects (4.6%) —
of these, 3.2% had diameters 3 cm to 4 cm, 1.4% had
diameters over 4.0.
3. When the ratio of
infrarenal to suprarenal diameters was used as the
definition, 112 aortas of less than 3.0 cm in diameter
were classified as having AAAs, and 201 aortas of 4.0 cm
or larger were classified as not having AAAs.
4. Smoking was the risk
factor most strongly associated with AAA. The odds ratio
(OR) for smoking among those with AAAs of 4.0 cm or
larger compared with those with normal aortas (infrarenal
diameter < 3.0 cm) was 5.5. The association of smoking
with AAA increased significantly with the years of
smoking, and decreased significantly with the number of
years after quitting smoking. The excess prevalence
associated with smoking accounted for 78% of all AAAs of
4.0 cm or larger. This suggests that smoking may be
responsible for most clinically important, previously
undiagnosed AAAs.
5. In all 3 models, age as
well as smoking was positively associated with AAA:
| Age |
Non-smokers |
Smoker |
| 50-55 |
0% |
0.3% |
| 75-79 |
0.8% |
2.7% |
6. Other positive
associations included coronary artery disease, high
cholesterol, hypertension, and family history of AAA.
DISCUSSION
- Smoking was the
factor most closely associated with AAA. "If
the association we observed between smoking and
AAA is assumed to be causal, then most of the
AAAs 4.0 cm or larger could be attributed to
smoking. AAA is a smoking-related illness."
- Only a small
proportion of patients reported a family history
of AAA, but it was an independent predictor,
supporting the hypothesis that at least some AAAs
have a genetic basis.
- This study was
limited to previously unrecognized AAA. The true
prevalence of AAA is therefore higher.
- "Our study
provides information that should be useful for
planning future screening programs...,but it does
not directly address whether such programs are
justified. This issue, which depends on the
quality of evidence that screening reduces
morbidity and mortality rates and is
cost-effective remains unsolved." The US
preventive task force considers that there is
insufficient evidence for or against screening (a
"C" recommendation).
CONCLUSION
Abdominal aortic aneurysm is associated with multiple
factors including age, high cholesterol, hypertension,
and coronary artery disease. In this study, smoking was
the risk factor most strongly associated with AAA and may
be responsible for most clinically important cases of
previously undiagnosed AAA.
Annals Int. Med. March 15, 1997; 126:441-49 Original
investigation from the Aneurysm Detection and Management
Veterans Affairs Cooperative Study Group, first author
from VA Medical Center, Minneapolis, Minn.
Comment:
This has obvious implications for screening. When we are
able to define sub-populations at increased risk,
screening becomes more productive. In men 65-69
prevalence of AAA 4.0 cm or larger in those who smoke and
have other atherosclerotic disease is over 1 in 50. RTJ
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