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| Raised Cholesterol
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Coronary artery disease progresses
during life, so that as many as 80% of the deaths associated with it occur
after the age of 65.
It occurs in
association with raised blood levels of LDL cholesterol,
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1 - although the relationship is less
striking with advancing years. A recent review summarizes the reasons for
treating hyperlipidemia in older people.
2 - Accumulation of lipids in the tissues occurs
with increasing age, although this effect is probably complete by old age (i.e.
over 80 years). It is due to the decreased activity of mechanisms that normally
reduce the amount of lipids in the blood; this may be caused by high
consumption of cholesterol and saturated fats over many years.
Uptake of LDL into the artery walls leads to
atherosclerosis. Estrogens have a protective effect by increasing the removal
of LDL from the blood. HDL, which is manufactured in the liver and intestine,
carries cholesterol from the tissues back to the liver, to be excreted in the
bile.
3 - HDL also checks the
uptake of lipids into the artery wall. High levels of HDL cholesterol are
associated with a low risk of coronary disease, which is why it is known as the
“good cholesterol”.
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Blood levels of HDL are lower in
men than in women from puberty onwards – probably an effect of male sex
hormones.
In
women, estrogens raise HDL levels, which fall again following menopause.
Aging does not
seem to affect HDL levels.
Raised blood cholesterol and/or
blood triglyceride levels are called hyperlipidemia. There are inherited types
of hyperlipidemia, but they are not often seen in older patients.
Life-long over-consumption of
dairy products and high-fat foods is an important contributing factor.
Hyperlipidemia
often occurs in patients with diabetes, kidney or thyroid disease, and, of
course, after menopause.
Several drugs can cause
hyperlipidemia: e.g. some diuretics, blood pressure medicines, steroids and
alcohol.
There is ample evidence
that treatment of hyperlipidemias in older people is beneficial. Several large
trials have proved that lowering blood cholesterol levels with drugs reduces
the rates of myocardial infarction (MI) and deaths due to MI. These benefits
were seen in patients over 65 years. An important question is whether lowering
blood lipid levels can reverse coronary atherosclerosis. Clinical studies have
shown this to be the case.
Although most of the studies have been done in young to middle-aged
men, it is quite reasonable to extend these findings to older persons.
Should all elderly
patients be screened for blood lipid abnormalities?
Widespread screening is not recommended, as there
is no evidence from good studies showing clinical benefit or cost
effectiveness. However, patients of any age with coronary artery disease, who
are in good health otherwise, should be tested.
Treatment should aim to lower the total
cholesterol level to 200 mg/dL, or the LDL-cholesterol level to 125 mg/dL. Diet
is the first line of treatment, and it works well in elderly patients. A
qualified dietician should advise patients on this. The total fat intake should
be reduced to less than 30% of dietary energy, with saturated, polyunsaturated
and monounsaturated fats each contributing roughly 10%. Cholesterol in the diet
should be less than 300 mg daily.
While moderate alcohol consumption may indeed have a beneficial
effect on coronary artery disease, patients with hyperlipidemia should avoid
it.
Moderate regular fish
consumption lowers plasma cholesterol in older people. If blood lipid levels
continue to be raised after 6 to 8 weeks of dieting, drug treatment should be
considered. The effectiveness and safety of antihyperlipidemic drugs are
similar in elderly and younger patients, although taking additional drugs in
the elderly may increase the risk of drug interactions.
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