A new study from the UK suggests that low levels of the "good" HDL cholesterol is linked to poor memory, and decline in memory, in middle aged adults.

The study is the work of researchers at University College, London, and is published in the 30th June issue of the Arteriosclerosis, Thrombosis and Vascular Biology journal of the American Heart Association.

The authors examined the relationship between fasting levels of blood fats and short term verbal memory in 3,673 male and female middle aged adults who were taking part in the Whitehall II longitudinal study.

Blood samples were taken at two measuring points: at mean age 55 and mean age 61, and tested for lipid or blood fat levels, including total cholesterol, high-density lipoprotein cholesterol (HDL-C), and triglycerides.

Whitehall II is a prospective study that started in 1985 and has been following over 10,000 male and female London-based members of the British Civil Service.

Using a statistical test called logistical regression, the researchers then looked for significant links between levels of HDL-C and memory deficit and decline.

High HDL-C was defined as being equal to or above 60 mg/dL or more, and low HDL-C was below 40 mg/dL.

The results were adjusted to take into account possible confounding factors, including education, job level, coronary heart disease, stroke, blood pressure, medications, diabetes, smoking and alcohol use.

Compared to having high HDL-C, having low HDL-C was linked to having a higher risk of memory deficit at the first (27 per cent higher risk) and second measuring point (53 per cent higher risk).

Decrease in HDL-C over the 5 year follow up was linked with memory decline (61 per cent higher risk).

The authors wrote that "no interaction with APOE e4 status was present".

APOE e4 is a gene that some studies have suggested may predispose people to Alzheimer's Disease.

The authors concluded that low HDL-C, which is potentially modifiable, is linked to "poor memory and decline in memory in middle-aged adults."