Twice as many people as previously thought are genetically predisposed to develop dangerously high cholesterol levels, new research suggests.
Early, consistent preventive care
Familial hypercholesterolemia, as this condition is called, significantly ups the risk for an early heart attack. The study found it affects about one in every 250 American men and women, rather than one in 500.
The new numbers don't reflect a problem on the rise, however, said study author Dr Sarah de Ferranti, an assistant professor of paediatrics at Harvard Medical School. Instead, the condition was previously "under-recognised", she explained.
Read: Familial hypercholesterolemia
For those who have this potentially deadly condition, "it is extremely important to get early, consistent preventive care", de Ferranti said.
"The key is for you and your clinician to understand and distinguish between mild to moderately high cholesterol that comes on in middle age related to a less than ideal lifestyle, and very high cholesterol that has been present since birth, which has allowed the high cholesterol to build up over decades," she explained.
If a close relative has a heart attack or chest pain before age 50, consider having other family members checked, she suggested.
Good treatment at the ready
Preventive measures include medication and lifestyle modification, de Ferranti noted. "We have very effective medications to lower cholesterol that we believe can reduce heart disease rates to the level of people without [familial hypercholesterolemia] if taken early enough and with good consistency," de Ferranti noted.
Read: Familial hypercholesterolemia: treatment
It's also important to maintain a healthy weight, watch what you eat and control blood pressure, she said. Not doing so can make your situation worse, she explained.
Dr Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles, agreed that while the risks are serious, good treatment is at the ready.
"Without treatment, men who have familial hypercholesterolemia frequently have heart attacks in their 40s and 50s, and women with familial hypercholesterolemia frequently have heart attacks in their 50s and 60s."
Once detected, "there are a number of very effective treatments that can lower the LDL cholesterol and prevent heart attacks and stroke in individuals with familial hypercholesterolemia", added Fonarow.
These include statin medications, medications that block cholesterol absorption, and the new PCSK9 inhibitors, he said. These are once- or twice-monthly injectable medications that help bring cholesterol levels under control.
Risk varies depending on ethnicity
The study results appear in Circulation.
"Up to now, we really haven't had a good estimate of how common familial hypercholesterolemia is in the U.S.," said de Ferranti. One reason for this is the diversity of the United States, she said. Rates of the genetic disorder vary based on racial/ethnic background, but most studies had focused on specific population groups, she explained.
The current effort, she noted, set out to rectify that problem.
Read: Knowing cholesterol better
The researchers analysed data concerning nearly 37,000 American adults enrolled in the 1999–2012 National Health and Nutrition Examination Survey.
To determine rates of familial hypercholesterolemia, they looked at levels of "bad" (LDL) cholesterol, a cause of plaque build-up in arteries. Then they looked for evidence of early heart disease, such as a heart attack or stroke at a young age, in individuals or their close relatives. The cut-offs were before 55 for men and before 60 for women.
Obesity boosts risk
Using a statistical model, the team concluded that roughly 834,500 Americans have this inherited condition.
Risk varied considerably depending on ethnicity: about one in 414 for Mexican-Americans; one in 249 among whites; and one in 211 among blacks.
Risk also appeared to differ with age, rising from one in every 1,557 adults in their 20s to about one in every 118 men and women in their 60s.
Obesity also boosted risk, the researchers found.
The new estimate includes both severe forms of the condition and potentially under-the-radar cases. That's because even relatively mild forms convey a "substantially higher risk for early heart disease", de Ferranti said.
What is cholesterol?
Causes of high cholesterol
Treating high cholesterol