High cholesterol may protect against infections and atherosclerosis.

However, the lack of exposure-response in the trials between changes in LDL-cholesterol and clinical and angiographic outcome, the inverse association between change of cholesterol and angiographic changes
seen in the observational studies, the significant increase in complicated atherosclerotic lesions in the treatment group after cholesterol lowering by diet, and most of all, the fact that high cholesterol predicts longevity rather than mortality in old people, suggests that the role, if any, of high cholesterol must be trivial.

The most likely explanation for these findings is that rather than promoting atherosclerosis, high cholesterol may be protective, possibly through its beneficial influence on the immune system.

Graham

http://qjmed.oxfordjournals.org/content/96/12/927.full