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Senior Citizen Health & Medicine
High Triglyceride Levels When Not Fasting May Point
to Heart Problems
One of two JAMA studies says reading after fasting
not associated with cardiovascular events
July 17, 2007 Two new studies indicate that high
triglyceride levels measured in persons that have not fasted prior to
the test are an indication of potential cardiovascular problems, such as
a heart attack. However, one of the studies finds that high triglyceride
levels found after fasting do not show this association.
An editorial in the July 18 issue of the Journal of
the American Medical Association that accompanies the two reports notes,
"For clinicians, it is important to recognize that when triglyceride
levels are between 150 and 1000 mg/dL, the risk for
atherosclerosis-related events is significantly increased."
Triglyceride levels are usually measured in the
fasting state, which could exclude certain types of lipoprotein
particles ("remnant" lipoproteins), a possible risk factor for
atherosclerosis. However, except for the first hours in the early
morning, most individuals are in the nonfasting state most of the time.
"Atherosclerosis may be a postprandial (occurring
after a meal) phenomenon in which remnant lipoproteins play a dominant
role. If this is true, increased levels of nonfasting triglycerides,
reflecting increased levels of remnant lipoproteins, may predict risk of
myocardial infarction (MI; heart attack), ischemic heart disease (IHD),
and death," the authors write.
Bψrge G. Nordestgaard, M.D., D.M.Sc., of Herlev
University Hospital, Herlev, Denmark, and colleagues tested the
hypothesis that very high levels of nonfasting triglycerides are
associated with an increased risk of heart attack, IHD, and death in the
general population. The study included 7,587 women and 6,394 men from
the general population of Copenhagen, age 20 to 93 years, who were
followed up from baseline (1976-1978) until 2004 (average follow-up 26
years).
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About Triglycerides |
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What are
triglycerides?
Triglycerides are the chemical form in
which most fat exists in food as well as in the body. They're
also present in blood plasma and, in association with
cholesterol, form the plasma lipids.
Triglycerides in plasma are derived from
fats eaten in foods or made in the body from other energy
sources like carbohydrates. Calories ingested in a meal and not
used immediately by tissues are converted to triglycerides and
transported to fat cells to be stored. Hormones regulate the
release of triglycerides from fat tissue so they meet the body's
needs for energy between meals.
How is an excess of triglycerides
harmful?
Excess triglycerides in plasma is called
hypertriglyceridemia. It's linked to the occurrence of coronary
artery disease in some people. Elevated triglycerides may be a
consequence of other disease, such as untreated diabetes
mellitus. Like cholesterol, increases in triglyceride levels can
be detected by plasma measurements. These measurements should be
made after an overnight food and alcohol fast.
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Read more at the American Heart Associaton |
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The researchers found that with increasing levels
of nonfasting triglycerides, levels of remnant lipoprotein cholesterol
increased. During the follow-up, 1,793 participants experienced a heart
attack, 3,479 developed IHD, and 7,818 died. In men and women, the
cumulative incidence of heart attack, IHD, and death increased with
increasing levels of nonfasting triglyceride levels.
Among women, the adjusted risk for heart attack
increased for each higher category of triglyceride levels (from 1-mmol/L
to greater than 5-mmol/L), with the increase in risk (adjusted for other
factors) ranging from 1.7 times to 5.4 times, compared to those with
triglyceride levels of less than 1-mmol/L. For men, the increased
adjusted risk for heart attack for each higher category of triglyceride
levels ranged from 1.4 to 2.4. Risk of IHD and death also generally
increased with higher triglyceride levels.
"We found that nonfasting triglyceride levels
independently predict MI, IHD, and death, particularly in women. These
findings may reflect the effects of remnant lipoproteins and therefore
may be of considerable interest when designing future trials of agents
aimed at reducing triglyceride levels or attenuating atherogenic
metabolic abnormalities. If our findings are confirmed, clinical care
might be simplified by using nonfasting lipid profiles for
atherosclerosis risk prediction," the researchers conclude.
Measurement of Non-Fasting Triglyceride Levels
Appears to Predict Risk of Cardiovascular Events Among Women
In the related study of over 25,000 initially
healthy women, higher triglyceride levels measured after not fasting is
associated with an increased risk for cardiovascular events, but his
association was not found for triglyceride levels measured after
fasting, according to a study in the July 18 issue of JAMA.
Sandeep Bansal, M.D., of Brigham and Womens
Hospital and the Harvard School of Public Health, Boston, and colleagues
conducted a study to determine the association of triglyceride levels
(fasting vs. nonfasting) and risk of future cardiovascular events. The
study included 26,509 initially healthy U.S. women (20,118 fasting and
6,391 nonfasting) participating in the Womens Health Study, enrolled
between November 1992 and July 1995. Triglyceride levels were measured
in blood samples obtained at time of enrollment.
During a median (midpoint) follow-up of 11.4 years,
1,001 participants experienced a new cardiovascular event (including 276
nonfatal heart attacks, 265 ischemic strokes, 628 coronary
revascularizations, and 163 cardiovascular deaths).
"In this large-scale, prospective cohort of
initially healthy U.S. women, we observed that higher nonfasting
triglyceride levels were strongly associated with an increased risk of
future cardiovascular events, independent of baseline cardiac risk
factors, levels of other lipids, and markers of insulin resistance. In
contrast, fasting triglyceride levels showed little independent
association with cardiovascular events. Associations were particularly
strong among individuals who had their blood drawn 2 to 4 hours after a
meal, and this relationship weakened as more time elapsed
postprandially," the authors write.
"Our observations may have implications for the
design and conduct of clinical trials evaluating triglyceride-lowering
medications. To date, almost all clinical trials of pharmaceutical
agents targeting triglyceride levels have relied on fasting levels as
inclusion criteria.
"However, if levels measured in the fasting state
are not the best marker for the atherogenicity associated with
hypertriglyceridemia, then it is possible that these trials might have
targeted the wrong patient populations. By contrast, previous studies
have demonstrated the benefits of several classes of drugs on
postprandial elevations in triglyceride levels.
"Thus, based on the data presented here, future end
point reduction trials of triglyceride-lowering agents might consider
participant inclusion on the basis of nonfasting rather than fasting
triglyceride levels."
Editorial: Triglycerides and Risk For Coronary
Heart Disease
In an accompanying editorial, Patrick E. McBride,
M.D., M.P.H., of the University of Wisconsin School of Medicine and
Public Health, Madison, comments on the two studies in this weeks JAMA
regarding triglyceride levels and risk of cardiovascular events.
"In the end, is it the triglyceride levels or the
associated changes in metabolism that explains the high risk associated
with postprandial triglyceride levels?
"This question is important scientifically, but in
clinical practice the argument may be as academic as the debate about
which came first, the chicken or the egg. For clinicians, it is
important to recognize that when triglyceride levels are between 150 and
1000 mg/dL, the risk for atherosclerosis-related events is significantly
increased.
"Therefore, it is important to aggressively and
comprehensively treat patients with dyslipidemias that include high
levels of triglycerides, low levels of HDL-C, and the presence of small
LDL-C particles, using both lifestyle change and medications if
necessary."
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