Lead author Archana Singh-Manoux of the French National Institute for Health and Medical Research in Paris and the University College London in England observed 3,673 Whitehall II participants. Whitehall II, which began in 1985, is long-term health examination of more than 10,000 British civil servants.

"Memory problems are key in the diagnosis of dementia," Singh-Manoux said in a statement. "We found that a low level of HDL may be a risk factor for memory loss in late mid-life. This suggests that low HDL cholesterol might also be a risk factor for dementia."

Researchers defined low HDL as less than 40 mg/dL and high HDL as 60 mg/dL or higher. The team compared blood-fat and memory data collected when study members were age 55 and 61.

The study found at age 55, participants with low HDL cholesterol showed a 27 percent increased risk of memory loss and at age 60, participants with low HDL had a 53 percent increased risk of memory loss.

The findings are reported in Arteriosclerosis, Thrombosis and Vascular Biology.