HEART OF THE MATTER
Knowing your personal heart disease risk can help
you live a healthier life with HIV, writes
Anna Poppa
Heart disease is the most common cause of early death in the UK, killing around
110,000 people every year. Heart disease affects some groups in society more
than others. It is more common in manual workers than non-manual workers,
and the risk of dying from heart disease is higher in people born in the Indian
sub-continent than in the UK, and in the north of the country compared to
the south.
Your personal risk of heart disease depends on a variety of factors. Major
risk factors that affect the general population are shown in the box (right).
Specific concerns for people with HIV are described in the next section. The
more risk factors you have, the greater your risk of heart disease. Reducing
risk factors like stopping smoking if you’re a smoker, improving your
diet, or becoming more physically active, can substantially reduce your risk.
Major risk factors for heart disease in the general population
Risk factors you are stuck with
• Older age
• Family history of early heart disease
• Pre-existing heart disease
• Diabetes
Risk factors you can change
• Smoking
• Unhealthy diet
• Lack of exercise
• Being overweight
• High blood pressure
Heart disease (including CVD, CHD and CVA) is a serious health condition which
occurs when the heart fails to get enough oxygen to function properly. The
heart’s oxygen supply can become restricted by the build up of fatty
material on the walls of the blood vessels that transport blood to the heart.
Over time, these fatty deposits may break off to form a clot, which can cause
a heart attack, or a stroke if the clot blocks the supply of blood to the
brain.
The image on the left shows the inside of a healthy blood vessel. The blood
vessel on the right has been narrowed by the build up of fatty deposits on
the vessel walls. This is called atherosclerosis, where the flow of blood
through the vessel and on to the heart is restricted. Atherosclerosis develops
slowly, and is associated with levels of fat in the blood, particularly cholesterol.
Cholesterol and other blood fats (lipids)
Cholesterol is a fatty substance made in the body from saturated fat we consume
through food. Cholesterol is used in the formation of cell membranes, but
too much in the blood can increase your risk of heart disease. The target
level for total blood cholesterol is under 5mmol/L. Two key components of
cholesterol are:
• LDL cholesterol: Low density lipoprotein, which carries cholesterol
from the liver to body cells. The target level for LDL cholesterol is under
3 mmol/L.
• HDL cholesterol: High density lipoprotein, which returns excess cholesterol
to the liver. The target level for HDL cholesterol is above 1 mmol/L.
Triglycerides are another fatty substance found in the blood. High triglycerides
can increase your risk of heart disease. The target level for triglycerides
is under 2 mmol/L.
Heart disease and HIV
There are some special reasons for considering your personal risk of heart
disease if you are HIV positive. It has been known for some time that fat
levels in the blood may be abnormal in people with HIV, including cholesterol
and triglycerides - two types important in determining heart disease risk
in the general population.
Since the introduction of more effective treatments for HIV (HAART), doctors
have become more concerned that these blood fat abnormalities may lead in
future to an increase in heart disease among people with HIV. This is because:
• Modern HIV treatments have extended survival, and so longer-term health
problems like heart disease have become more relevant to people with HIV.
• Some HIV treatments cause specific blood fats to increase, and may
be linked with atherosclerosis.
• Risk factors for heart disease appear to be more common in HIV positive
people than in the general population.
There is good evidence that, over the short-term, the additional risk of heart
disease which may occur due to taking HIV treatment does not outweigh the
benefits that treatment provides by controlling HIV. Whether this balance
will shift over the longer-term is unknown, though researchers have shown
that the length of time spent on HIV treatment leads to an incremental rise
in the risk of heart disease, stroke and related conditions.
According to the latest report from a large, international research study
called DAD, set up to investigate the longer-term safety of HIV treatments,
each year spent on HIV combination therapy increases the risk of having a
heart attack by 17 per cent. Standard risk factors such as smoking, age, raised
cholesterol and triglycerides, and gender have also been proven to be important
predictors of risk in the DAD study, underlying the fact that use of HIV treatments
must be considered in the context of other risk factors for heart disease.
Because HIV treatment may contribute to the long-term risk of heart disease
in people with HIV, it is recommended that HIV treatments should be chosen
according to your personal risk of heart disease. This should be done in addition
to considering the usual risk factors and ensuring your HIV disease is controlled
effectively. Some HIV treatments appear to have little effect on heart disease
risk. In an interview on page 36, Dr Graeme Moyle from the Chelsea and Westminster
Hospital, London, discusses a recent clinical trial which explores this area.
Calculating your risk
Doctors estimate your personal risk of heart disease by referring to statistics
gathered from a long-running American research study. The Framingham Heart
Study was set up 50 years ago to investigate the causes of heart disease in
the American population. This study is used today to predict a person’s
individual risk of heart disease, over a ten year period, based on a series
of personal risk factors:
• Age
• Total (or LDL) cholesterol
• HDL cholesterol
• Blood pressure
• Diabetes
• Smoking
A simplified version of the Framingham Heart Study Database is available online
(see Help on the web on page 40).
This calculator allows you to work out your estimated risk yourself, so long
as you know your total and HDL cholesterol levels, and your blood pressure.
The example below shows how a heart disease risk calculation is performed,
and illustrates the effect which making changes to your lifestyle might have
on your future risk of heart disease.
David
David is 42 and has been HIV positive for eight years. He is planning to start
HIV treatment soon, and has been advised by his doctor that when choosing
his combination he should consider, among other things, his existing risk
of heart disease, as taking HIV treatment may add to this.
David does not have heart disease, and is not diabetic. He smokes 20 cigarettes
a day, and goes to the gym for one hour, four times a week. His total cholesterol
level is 6.47 mmol/L (higher than it should be), his HDL level is 0.78 mmol/L
(lower than it should be), and his blood pressure is 130/85 (about right).
Table 3 illustrates David’s risk of having a heart attack over the next
ten years, according to three different scenarios. These are examples of changes
which David might make to his lifestyle in order to reduce his risk:
• Option 1: David makes no changes to his lifestyle.
• Option 2: David stops smoking.
• Option 3: David switches to a low-fat diet which reduces his blood
cholesterol level by 10% to 5.82.
Estimating David’s ten-year risk of heart attack using the Framingham
calculator
| Risk Factor | risk Option 1 No change |
21% Option 2 Stop smoking |
5% Option 3 Low-fat diet |
| Age | 42 | 42 | 42 |
| Sex | Male | Male | Male |
| total cholesterol | 6.47 | 6.47 | 5.82 |
| HDL cholesterol | 0.78 | 0.78 | 0.78 |
| Smoker | Yes | No | Yes |
| Systolic blood pressure | 130 | 130 | 130 |
| Ten year heart attack risk | 21% † | 5% ‡ | 16% * |
† An estimated 21 out of every 100 people with these risk factors will
have a heart attack in the next ten years.
‡ An estimated 5 out of every 100 people with these risk factors will
have a heart attack in the next ten years.
* An estimated 16 out of every 100 people with these risk factors will have
a heart attack in the next ten years.
From David’s calculation it is clear that stopping smoking would cause
greatest reduction in his calculated 10 year cardiovascular risk.
Help on the web
• 10-Year Heart Disease Risk Calculator hin.nhlbi.nih.gov/atpiii/calculator.asp
• British Heart Foundation http://www.bhf.org.uk
• QUIT http://www.quit.org.uk/
Anna Poppa is a freelance medical writer, annapoppa@tiscali.co.uk
