The Pulse: Doc, Is My Cholesterol Too High?

In The Pulse, a new monthly column, Dr. Jerome Zisfein will offer facts and guidance to help readers understand medical topics of general interest.

Many patients ask me, “What is a normal cholesterol level?”

My answer…”it depends.”

Your blood cholesterol level is one of many things that go into determining your risk of developing heart disease. Other factors include your genes, age, sex, blood pressure, diabetes and smoking.

There are no real normal values for blood cholesterol. There are, however, desirable values, which depend on the individual clinical factors of each person and a rough estimate of their risk of having a heart attack, stroke or heart-related death in the future.

For instance, a 65-year-old patient who recently had a heart attack, is at much higher risk for future heart attacks than a 40-year old with no past medical history.

When your doctor tests your cholesterol level, the test that is ordered is a “lipid profile,” which includes total cholesterol, LDL cholesterol (“bad cholesterol”), HDL cholesterol (“good cholesterol”) and triglycerides.

High LDL is usually considered bad because this is the cholesterol that is deposited in the walls of your arteries, causing blockage, whereas high HDL is considered good in that it seems to protect against the deposition of LDL. Lowering LDL in your blood will decrease the chances of blockages forming.

This can be done through eating a heart-healthy diet and medications such as statins. Unfortunately, however,  there is no reliable way to raise HDL (the good cholesterol) enough to have an impact on LDL deposition. And although a high triglyceride level may be bad, lowering it for most people doesn’t seem to help much.

There is a large amount of scientific evidence showing that lowering LDL cholesterol decreases a person’s future risk of heart disease caused by blocked arteries.

How much lower? Eating a healthy diet usually reduces LDL by 10% or less. Taking a statin will generally lower a person’s LDL by 30-50% and reduce their cardiac risk by 25-30% over the next 10 years.

So shouldn’t we all be on a statin or other cholesterol-lowering medication? Let’s get back to our example at the top of this article.

Our 65-year-old man with a recent heart attack has a 25% risk of having another heart attack over the next 10 years. If he takes a statin, he can reduce his risk by 30%, to about 17%. But our healthy 40-year-old has a much lower risk to start with, say 2% over 10 years; taking a statin will have a very small impact on his health.

So, people who have had a heart attack, stroke or procedures to fix clogged arteries (stents, bypass surgery) should usually be on statins.

What about other people who haven’t had heart attacks, strokes or cardiac procedures?

Just as we used the risk estimates of our two people above to decide if taking a statin is worthwhile, we can do the same for people whose risk is between these two extremes.

We can estimate any person’s 10-year cardiac risk by taking into account their various risk “factors,” such as cholesterol values, age, sex, high blood pressure, diabetes, smoking and family history of heart disease.

There are various online calculator tools that can help with estimating risk (such as the ACC ASCVD Risk Estimator). The American Heart Association currently recommends starting cholesterol-lowering medication for people with an estimated 10-year cardiac risk of 7.5-9% or more.

If a person’s 10-year risk is borderline or if he/she is reluctant to take medication, their doctor might also recommend a Coronary Calcium Score scan to assess calcium deposit in the coronary arteries. The presence and amount of calcium detected in the coronary arteries can be used to further estimate your cardiac risk.

For those people with intermediate risk, a frank discussion with their doctor should explain how much benefit they are likely to get from taking a pill for the next 10 years. The lower a person’s 10-year risk is, the less they will benefit from taking a statin.

So, what is a desirable cholesterol value? As I said before…it depends.

For those with a high (more than 20%) 10-year cardiac risk, an ideal LDL is less than 70 mg/dl.

For those with intermediate risk (9-20%), the goal is less than 100.

And for those with low risk (less than 7.5-9%), taking a statin will not have much impact on future health.

What about people who cannot take statins because of side effects or who cannot attain their LDL goal on full dose statins? Fortunately, there are other medications that can be used either alone or in combination with statins.

Of course, lowering your cholesterol with statins or other drugs is only one aspect of lowering the risk of heart disease.

Eating a well–balanced diet, regular exercise, smoking avoidance and adequate blood pressure and diabetes control will all contribute to a long, heart-healthy life.

Dr. Jerome Zisfein is a practicing cardiologist with a special interest in education of medical trainees as well as providing information to patients and the public. You can send him your questions to be answered in a future column at [email protected]