Fibrinogen is a protein that plays a key role in blood
clotting. Fibrinogen is a sticky,
fibrous coagulant in the blood that appears to significantly increase the risk
of experiencing one of the leading causes of death and disability - stroke.
Analysis of the large-scale
EUROSTROKE project (J Epidemiol Community Health 2002;56(Suppl I):i14-i18) showed that
"fibrinogen is a powerful predictor of stroke" - including fatal and
nonfatal strokes, first time strokes, and hemorrhagic and ischemic
strokes. Dividing the population into four groups (quartiles) based on their
fibrinogen levels, researchers estimated that the risk of stroke increased by
nearly 50% for each ascending quartile. Individuals whose fibrinogen levels
were in the highest quartile were almost seven times more likely to suffer a
hemorrhagic stroke, and more than twice as likely to die from a stroke.
Importantly, higher levels of
fibrinogen raised the risk of stroke independently of cardiovascular risk
factors such as smoking and hypertension. Still, high blood pressure and high
fibrinogen levels appeared to be the most dangerous combination, elevating a
person's risk of stroke even more. Each
year, strokes account for about 1 of every 15 deaths in the United
States. More than one-fourth of the people
who suffer a stroke are under age 65.
A recent study measured baseline
fibrinogen levels in over 2000 men and women being treated at a preventive
cardiology unit of a large city hospital. About half of the patients had coronary artery
disease (CAD). Acevedo M et al (Am Heart
J 2002;143:277-82) found that patients with CAD tended
to have higher fibrinogen levels than those without the disease. Of the
patients whose fibrinogen levels fell within the two highest quartiles (>331
mg/dL), about 75% of men and 50% of women were
diagnosed with clinical CAD. A previous history of heart attack in the group
with CAD was also associated with significantly higher average levels of
fibrinogen.
These results show that patients
with CAD, particularly those who have experienced a heart attack, often have
higher fibrinogen levels. But are
elevations of this marker merely an after-effect of the disease? To find out, investigators further tracked
the health of the patients for an average of 24 months after their treatment at
the cardiac care unit. They discovered fibrinogen was a strong and significant
independent predictor of death from all causes in both men and women. The percent mortality rate jumped by over
seven-fold in those with the highest fibrinogen levels, compared to those with
the lowest levels.
Fibrinogen's association with
increased mortality is probably directly related to its ability to promote
thromboses, or clots, by causing platelets to clump inside blood vessels. This is one of the main mechanisms underlying ischemia and heart attack. Exercise, quitting smoking, and
certain medications have been shown to lower fibrinogen in the short term.
A number of studies show elevated fibrinogen to be a major
risk factor for coronary heart disease (heart attacks) and cerebrovascular
disease (strokes), which together account for about 60% of deaths in the
elderly. In fact, fibrinogen may possibly be the major risk factor, exceeding
the “contributions” of homocysteine, cholesterol and other lipids in the
pathogenesis of these diseases. Elevated
fibrinogen levels have also been associated with a number of other diseases,
including cancer, diabetes and hypertension (N Engl J Med, 1987, 317: 521; The
Framingham Study. JAMA, 1987, 258: 1183).
SG Thomson, et al prospectively studied over 3,000 patients
with angina pectoris (chest pain due to coronary artery insufficiency) in his
1995 New England Journal of Medicine article (332: 635-641) and found if
fibrinogen levels were low, even highly elevated levels of cholesterol and/or
C-reactive protein presented little risk of heart attacks. However, high levels
of fibrinogen in combination with low-moderate levels of cholesterol presented
a significant risk.
Fibrinogen levels have been shown by a number of research
teams to rise about 25 mg/dl per decade of age (Yarnell in Circulation, 1991,
83: 836-844; Fu and Nair in Am J Physiology 275 (Endocrinol Metab 38), 1998
E1203-E1030) even if they are described as being in good health. A team of scientists in China
also recently compared fibrinogen levels in two families, one family with a
history of long life in many of its members, compared to another family with
traditionally shorter life expectancies. The scientists concluded that low
plasma fibrinogen levels are correlated with longer life (Wang, et al, Weisheng
Yanjiu, 1998, 27: 5, 315-316).
No drug (with the possible exception of estrogen) or
lifestyle change is known to significantly alter fibrinogen levels, although
quitting smoking does result in slight reductions in fibrinogen levels.
However, for those of us who don’t smoke, there has been little, if any, advice
which could be given to lower fibrinogen from the conventional medical
approach.
Nutritional supplements can reduce fibrinogen levels and
the presumably the inherent risk of hyper-fibrinogenemia-related diseases. Ramirez-Bosca’s studies in Spain have
demonstrated that certain antioxidants are capable of dramatically reducing
blood levels of lipid peroxides and oxidized lipoproteins (Age 1995, 167-9 and
in 1997, 20: 165-8) after only 15 days with no adverse effects noted by any of
the subjects or adverse changes in any other blood chemistries (Mech Aging Dev,
2000, 114: 207-20).
