(NEW YORK) — More than 40% of adults in the United States are unaware they have — and therefore are not being treated for — high cholesterol, according to a new study.

For the study, published in JAMA Cardiology, researchers from institutions in New York, Texas, Louisiana, Pakistan and Egypt looked at data from the National Health and Nutrition Examination Survey between 1999 and 2020 examining patients at least ages 20 and older with cholesterol levels above 160 mg/dL (milligrams per deciliter).

Less than 150 mg/dL is considered normal, according to Johns Hopkins Medicine. Between 150 and 199 mg/dL is borderline high, 200 to 499 mg/dL is high, and 500 mg/dL is very high.

Survey data was examined to see if adults had been informed about their above normal or high cholesterol levels, or were being treated.

Adults were classified as unaware if they had never had a measurement or were never told about the measurement.

They were classified as untreated if they had not been prescribed specific cholesterol lowering medications including statins.

Not treating high cholesterol can lead to plaque accumulating inside blood vessels, which can lead to a heart attack or a stroke.

Overall, fewer were unaware they had high cholesterol levels and were not treating them in 2020 than in 1999, but percentages were still high.

Among those with a cholesterol level of 160 mg/dL or higher, 49.4% were unaware and untreated in 1999, declining to 38.5% in 2020.

The study also found that younger adults, men, those without insurance, and Hispanic populations had higher rates of being unaware and untreated. Those with lower education level and lower socioeconomic groups also had higher rates of untreated elevated cholesterol.

Approximately two-thirds of adults in the U.S. report having had their cholesterol levels checked within the last five years, according to the Centers for Disease Control and Prevention.

Most healthy adults should have their cholesterol checked every four to six years. Some people, such as those who have heart disease, diabetes, or a family history of high cholesterol, should get get their cholesterol checked more often.

The authors note that although the prevalence of severely elevated cholesterol levels has declined in the last two decades, 1 in 17 still have levels in the borderline high category and 1 in 42 have high levels.

“This lack of awareness and treatment may be due to difficulties accessing primary care, low rates of screening in primary care, lack of consensus on screening recommendations, insufficient emphasis on [low-density lipoprotein cholesterol] as a quality measure and hesitance to treat asymptomatic individuals,” the authors wrote.

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