High levels of low-density lipoproteins (LDL), the “bad” cholesterol, have long been associated with memory problems experienced by the elderly but new research on the effects of the high-density lipoproteins (HDL), shows that high levels of the “good” cholesterol in middle age are beneficial in maintaining good memory well into the twilight years and may reduce the chances of developing age-related dementia.

HDL and memory lossThe British Whitehall II study, a long-term study of the health of more than 10,000 British civil servants, isolated 3,673 study participants, of whom 26.8% were women, during phases 5 and 7 of the study, which began in 1985, to analyze the effect of HDL on memory function as the study participants reached middle age.

The presence of memory impairment in middle age is a strong indicator of dementia developing later in life.  People who are 65 years and older are the fastest growing age group in the world’s industrialized countries and are at the most risk of developing dementia.

For the sake of the study, a low level of HDL was considered to be 40 mg/dL while 60 mg/dL or higher was considered high.  Performance on memory tests and blood-fat content were compared from phase 5 of the study, conducted in 1995, when study participants were of the average age of 55, to the same study participants when their average age was 61, during phase 7 of the study in 2002.

The memory tests involved a participant’s ability to recall 20 short words read to them one word at a time at an interval of two seconds per word.  After hearing all 20 words, consisting of only one or two syllables, the participant was given two minutes to write down as many words as he or she could remember.

Key findings include:

  • At 55 years of age, participants who were found to have low levels of HDL were at 53% higher risk of impaired memory than those with high levels of HDL.
  • By age 60, those with low HDL levels were at 53% risk of memory loss.
  • During the five-year interval between phases 5 and 7, study participants who experienced a drop in HDL were at 61% risk of losing their ability to remember the words than participants with high levels of HDL.
  • Researchers first segregated studies between men and women but there was no significant difference discerned between genders so data was combined for the study.
  • There was no association between memory loss and the level of total cholesterol or triglycerides.
  • Statin drugs, prescribed to raise HDL while lowering LDL, produced no effect on memory loss.

Previous research has shown that a high level of HDL lowers the risk of heart attack, aids numerous biological processes, removes excess cholesterol from the bloodstream, helps nerve cells develop, and controls the production of beta-amyloid.  Alzheimer’s disease patients have a build-up in the brain of protein plaques that contain high levels of beta-amyloid.

The statin class of drugs can lower levels and improve the balance between HDL and LDL but they come with a risk of heart disease.  Drug-free lifestyle changes recommended by the American Heart Association include regular exercise; avoiding dietary trans fats; minimizing all fats in the diet, with special emphasis on avoiding saturated fats; and relying instead on monounsaturated fats, of which olive, canola, and peanut oils are recommended.

Full details of this aspect of the Whitehall II study can be found in Arteriosclerosis, Thrombosis and Vascular Biology, a journal published by the American Heart Association.

Funding for this on-going study has been provided by the British Medical Research Council; the British Health and Safety Executive; the British Heart Foundation; the British Department of Health; the National Institute on Aging; the National Heart, Lung, and Blood Institute; and the John D. and Catherine T. MacArthur Foundation Research Networks on Successful Midlife Development and Socioeconomic Status and Health.

Source: American Heart Association