"Good" cholesterol may protect memory, study finds

At age 55, those with low HDL cholesterol had a 27-percent higher risk of memory loss when compared to those with high HDL. At age 60, those with low HDL had a 53-percent higher risk of memory loss compared to those with high HDL levels.

The study did not track whether or not the people went on to develop dementia.

Low HDL was defined as less than 40 milligrams per deciliter (mg/dL) and high HDL was defined as at least 60 mg/dL in the study, published in the American Heart Association's journal Arteriosclerosis, Thrombosis and Vascular Biology.

Cholesterol is a fatty substance made naturally by the body and also found in many foods. High HDL levels can cut heart attack risk.

As opposed to low-density lipoprotein (LDL) cholesterol that can build up in artery walls, making them hard and narrow, HDL cholesterol takes excess cholesterol back to the liver.

LDL cholesterol is dubbed the "bad" cholesterol.

In the study, total levels of cholesterol and triglycerides

-- another type of fat found in the blood -- had no association with memory decline.

Singh-Manoux said the study did not look at the reasons that HDL cholesterol may protect memory. She said one possible explanation is that it wards off formation of beta-amyloid plaques in the brain that are a hallmark of Alzheimer's.