Beware of Very High 'Good' Cholesterol Levels - Not All That Good

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Highlights:

• Very high levels of HDL or "good" cholesterol may not be heart protective and could increase risk of suffering a heart attack or dying due to heart disease
• The reasons for this phenomenon remain unclear and more studies may be necessary in future to find out the cause
• Traditionally, doctors have been telling patients to follow dietary and other measures to increase HDL cholesterol levels as it was considered good for their heart health, however it may not be true in all cases

Very high levels of high-density lipoprotein (HDL) or good cholesterol may be harmful to the heart and could increase the risk of heart attack or death due to heart disease, according to a recent study led by Dr Marc Allard-Ratick, of Emory University School of Medicine, Atlanta, US. The findings of the study were presented at the European Society of Cardiology (ESC) Congress.

Dr. Allard-Ratick says, "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. However, the results from this study and others suggest that this may no longer be the case."

Very High HDL Cholesterol Levels and Relationship to Heart Disease

The current study, undertaken as part of the Emory Cardiovascular Biobank, analyzed the association between very high HDL cholesterol values and the risk of heart attack and death.

• The study included 5,965 participants, most of whom had an underlying history of heart disease
• The average age of persons taking part in the study was 63 years and 35 percent were women
• All participants were segregated into five groups based on HDL cholesterol levels -
• Values less than 30 mg/dl (0.78 mmol/L)
• 31-40 mg/dl (0.8-1 mmol/L)
• 41-50 mg/dl (1.1-1.3 mmol/L)
• 51-60 mg/dl (1.3-1.5 mmol/L); and
• Higher than 60 mg/dl (1.5 mmol/L)

The participants were followed up over a median follow-up period of four years during which 769 (13%) participants suffered a heart attack or died from a heart-related cause.

‘Levels of HDL cholesterol more than 60 milligrams per deciliter is associated with higher risk of heart attack or dying from a heart-related cause.’

The key findings of the study included the following:

• Persons with HDL cholesterol between 41-60 mg/dl (1.1-1.5 mmol/L) showed the least risk of heart attack or death due to heart disease
• However, the risk was higher in the groups that had low levels (less than 41 mg/dl) and very high levels (greater than 60 mg/dl) of HDL cholesterol, forming a U-shaped curve when plotted graphically
• Interestingly, those with HDL cholesterol levels more than 60 mg/dl (1.5 mmol/L) had a nearly twice the risk of suffering a heart attack or dying due to heart disease compared to those with optimum HDL cholesterol levels of 41-60 mg/dl (1.1-1.5 mmol/L).
• The associations remained constant even after adjusting for other confounding risk factors for heart disease such as smoking, diabetes, smoking, low-density lipoprotein (LDL or "bad") cholesterol, as well as other factors associated with high HDL cholesterol values such as race (Hispanics, non-Hispanic whites and Asians), sex and alcohol intake.

Thus, the findings of the study suggest and also support similar findings from earlier studies that found very high HDL cholesterol levels to be associated with an increased risk of heart attack and death due to heart disease.

Dr. Allard-Ratick said, "Our results are important because they contribute to a steadily growing body of evidence that very high HDL cholesterol levels may not be protective, and because unlike much of the other data available at this time, this study was conducted primarily in patients with established heart disease."

Conclusion

Although more studies in future may be necessary to determine the reasons why very high HDL cholesterol levels adversely affect the heart, Dr. Allard-Ratick believes that the very high levels may actually represent abnormal HDL cholesterol not doing their normal heart protective function properly. The oft-repeated mantra - "HDL cholesterol is good cholesterol" may not be true for all.

Reference:

1. Too much of a good thing? Very high levels of "good" cholesterol may be harmful - (https:www.escardio.org/The-ESC/Press-Office/Press-releases/Too-much-of-a-good-thing-Very-high-levels-of-good-cholesterol-may-be-harmful)

Source: Medindia

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