Why having too much 'good cholesterol' may actually be a bad thing

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Researchers say extremely high levels of HDL cholesterol result in greater mortality rates

For years, doctors have encouraged consumers to lower their levels of “bad” cholesterol -- low-density lipoprotein (LDL). But they have counseled them that high levels of “good” cholesterol – high-density lipoprotein (HDL). -- are OK.

Now a new study shows that high levels of HDL can also be harmful.

Researchers from the University of Copenhagen say that people with extremely high levels of good cholesterol are still at higher risk of mortality than those with normal levels. The finding challenges many preconceptions that the medical community has had about HDL up to this point.

"These results radically change the way we understand 'good' cholesterol. Doctors like myself have been used to congratulating patients who had a very high level of HDL in their blood. But we should no longer do so, as this study shows a dramatically higher mortality rate," says study author Børge Nordestgaard.

Greater mortality rates

Nordestgaard and his colleagues analyzed health information on 116,000 patients who took part in two extensive medical studies, as well as mortality data from the Danish Civil Registration System. Their overall findings were based on six years of tracking on nearly 11,000 deaths.

Results from the analysis indicated that men with extremely high HDL levels in their blood had a mortality rate that was 106% higher than men with normal HDL levels. For women with extremely high HDL levels, the mortality rate was 68% higher.

However, the researchers say that having low levels of HDL was also found to be dangerous, while those with medium levels had the lowest mortality among all patients. Nordestgaard hopes that the findings will help change doctors’ perspective of HDL so that they can give patients more relevant information and improve health outcomes.

"It appears that we need to remove the focus from HDL as an important health indicator in research, at hospitals and at the general practitioner. These are the smallest lipoproteins in the blood, and perhaps we ought to examine some of the larger ones instead. For example, looking at blood levels of triglyceride and LDL, the 'bad' cholesterol, are probably better health indicators," he said.

The full study has been published in the European Heart Journal

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