Both high and low levels of high-density lipoprotein (HDL) cholesterol - commonly called 'good cholesterol' for helping reduce the risk of stroke and heart attack - may increase a person's risk of premature death, a new study has claimed.
Conversely, intermediate HDL cholesterol levels may increase longevity, researchers said.
"The findings surprised us. Previously it was thought that raised levels of the good cholesterol were beneficial," said Ziyad Al-Aly, professor at Washington University in the US.
"The relationship between increased levels of HDL cholesterol and early death is unexpected and not fully clear yet. This will require further study," said Al-aly.
Cholesterol is a fatty substance found in blood that can narrow and block heart vessels, causing cardiovascular disease and stroke. For years, HDL cholesterol has been credited with helping to remove plaque-building "bad cholesterol" from arteries, researchers said.
They studied kidney function and HDL cholesterol levels in more than 1.7 million male veterans from October 2003 to September 2004. Researchers then followed participants till September 2013.
Patients with kidney disease frequently have lower levels of HDL cholesterol, which might explain their increased risk of early death; however, the association between elevated HDL cholesterol levels and premature death in these patients has been unclear, researchers said.
In this study, researchers showed that both high and low HDL cholesterol levels were associated with an increased risk of dying among study participants with all levels of kidney function.
"The findings may explain why clinical trials aimed at increasing HDL cholesterol levels failed to show improved outcomes," said Al-Aly.
Research data showed a relationship between HDL cholesterol levels and mortality as a U-shaped curve with the risk of death increased at both ends of the spectrum.
"Too low and too high are both associated with higher risk of death," said Al-Aly.
The findings were published in the Clinical Journal of the American Society of Nephrology
Courtesy – Deccan Herald