Contrary to claims that good cholesterol is beneficial to the heart, a new study has showed that very high levels may be associated with an increased risk of heart attack and death.
The findings showed that people with high-density lipoprotein (HDL or "good") cholesterol levels of 41-60 mg/dl (milligrams per decilitre) had the lowest risk of heart attack or cardiovascular death.
However, the risk increased in people with low levels (less than 41 mg/dl) as well as very high levels (greater than 60 mg/dl) of HDL cholesterol.
People with HDL cholesterol levels greater than 60 mg/dl had a nearly 50 per cent increased risk of dying from a cardiovascular cause or having a heart attack compared to those with HDL cholesterol levels 41-60 mg/dl.
"It may be time to change the way we view HDL cholesterol. Traditionally, physicians have told their patients that the higher your 'good' cholesterol, the better," said Marc Allard-Ratick, from the Emory University in Atlanta, US.
"However, the results from this study and others suggest that this may no longer be the case," he added.
The bad effects of very high HDL cholesterol were consistent even after controlling other risk factors for heart disease such as diabetes, smoking, and low-density lipoprotein (LDL or "bad") cholesterol, as well as other factors such as alcohol intake, race, and sex.
HDL cholesterol has been considered "good" because the HDL molecule is involved in the transport of cholesterol from the blood and blood vessel walls to the liver and ultimately out of the body, thereby reducing the risk of clogged arteries and atherosclerosis, the researchers explained.
The study investigated the relationship between HDL cholesterol levels and the risk of heart attack and death in 5,965 individuals, most of whom had heart disease.
The results were presented at the ESC Congress 2018, the annual conference of the European Society of Cardiology in Munich, Germany.