In the United States, 73.5 million adults (31 percent) have high levels of low-density lipoprotein (LDL), or "bad" cholesterol. Yet not even half of adults with high LDL cholesterol are getting treatment to lower their levels. Less than 1 out of every 3 adults (29.5 percent) with high LDL cholesterol has the condition under control.

Familial hypercholesterolemia is a genetic disorder caused by a defect on chromosome 19. Patients who experience high cholesterol due to an inherited genetic disorder from one of their parents — heterozygous familial hypercholesterolemia — are much more likely than those with average cholesterol levels to have diseases caused by hardening of the arteries, including an accelerated onset of coronary heart disease by up to 30 years.

Familial hypercholesterolemia is suspected when an individual has an LDL cholesterol level greater or equal to 190 mg/dL in the setting of a family history of premature cardiovascular events. A new study in the journal Circulation examined the relationship between cardiovascular disease and familial hypercholesterolemia.

Using pooled data from six groups of people in epidemiological studies (with 1.2 million person-years of follow-up), researchers found patients with the familial hypercholesterolemia phenotype were at five times higher risk for coronary heart disease over the long term (up to 30 years), compared to those with average levels (less than 130 mg/dL) of LDL cholesterol.

They were ­ also more likely to have diseases caused by hardening of the arteries (atherosclerotic cardiovascular disease), including an accelerated onset of coronary heart disease by up to 20 years earlier in men and 30 years earlier in women. These increased risks were independent of other risk factors.

What distresses familial hypercholesterolemia specialists is that while the condition is common and affects more than 600,000 in the U.S., it is diagnosed in less than 10 percent of those who suffer from it. The need for heightened awareness of what's behind high cholesterol is clear: Familial hypercholesterolemia accounts for 20 percent of heart attacks in people less than 45 years old.

Researchers recommend that clinician-patient discussions about guideline-supported therapies should include the scenario that a 25-year-old woman with newly diagnosed familial hypercholesterolemia has a risk of coronary heart disease death or nonfatal heart attack comparable to that for a 55-year-old woman — if her cholesterol were to remain untreated.

Such an analogy, paired with counseling about how to improve risk, may motivate behavioral changes as well as adoption of and adherence to evidence-based medications. This is important because familial hypercholesterolemia can be treated with cholesterol-lowering drugs to decrease the risks for coronary heart disease and stroke.