People who have high cholesterol due to an inherited genetic disorder are much more likely than those with average cholesterol levels to have diseases caused by hardening of the arteries, according to new research in the American Heart Association journal Circulation.

Heterozygous familial hypercholesterolemia is due to a genetic mutation that prevents the liver from removing excess low-density lipoprotein, known as “bad” LDL cholesterol, from the blood. The disorder is suspected when a person has an LDL level greater or equal to 190 mg/dL and is in a family with a history of premature cardiovascular events.

Researchers estimate that the disorder affects about 1.5 million Americans.

Using pooled data from six groups of people in epidemiological studies, researchers found that patients with the familial hypercholesterolemia phenotype:

  • Had five times higher risk for coronary heart disease over a period up to 30 years, compared to those with average levels (less than 130 mg/dL) of LDL cholesterol, and
  • Were 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.

Researchers say that their findings may help clinicians communicate more clearly to patients the risks of familial hypercholesterolemia, which can be treated with cholesterol-lowering drugs to decrease the risks for heart disease and stroke.