Here's an apparent paradox: high levels of artery-clogging cholesterol are a risk factor for heart disease. But such high levels have been linked to improved outcomes after a heart attack and other acute heart "events".
Now, new research suggests that this paradoxical finding may simply stem from not taking other factors into account.
People with heart problems and very high cholesterol levels may fare better because they're more likely to be treated with a cholesterol-lowering "statin" drug, researchers report in the journal Clinical Cardiology. Such drugs lower levels of so-called "bad" cholesterol, otherwise known as LDL cholesterol.
Perhaps, more importantly, a diagnosis of very high cholesterol – what doctors call hypercholesterolaemia – may simply identify patients who have seen their doctors. The thinking is that such patients are more closely watched by their doctors, so they end up doing better than those with low cholesterol who may still be at some risk.
History of high cholesterol protects
The results are based on a study of 84,429 patients enrolled in a study designed to encourage doctors to use well-established guidelines when treating patients with heart problems caused by reduced blood flow to the heart.
Patients with a history of high cholesterol were 42% less likely to die while hospitalised than were those without this history, Dr Tracy Wang, from Duke Clinical Research Institute, North Carolina, and colleagues found.
The association remained strong after the researchers accounted for other factors, including use of cholesterol-lowering statin drugs.
In looking at 22,711 patients with no history of high cholesterol, Wang's team identified 12,809 who were diagnosed with high cholesterol during a hospitalisation for heart problems.
Although the initial analysis suggested a reduced risk of death with high cholesterol, that reduction disappeared when researchers took other factors into account.
This study, the researchers conclude, confirms the well-documented association of high cholesterol with better outcomes among heart patients and further demonstrates that patients with newly diagnosed high cholesterol don't necessarily enjoy this potential protection.
(Reuters Health, October 2009)
Read more: A wider use for statins