Low "Good" Cholesterol May Rob Your Memory-Study

Low levels of so-called good cholesterol may significantly increase middle-aged people’s risk of developing progressive loss of memory and dementia later in life, a new study by European researchers suggested Monday.

Physicians often advise people to try to keep up their levels of high-density lipoprotein (HDL) or "good" cholesterol in order to keep their risk of heart disease at bay. Now the new research suggests that the high levels of such cholesterol may also help prevent a decline in memory.

The study appears in the July 1 edition of the American Heart Association’s journal Arteriosclerosis, Thrombosis and Vascular Biology.

In their study the research team, lead by Dr. Archana Singh-Manoux Ph.D., lead author of the study and Senior Research Fellow with the French National Institute for Health and Medical Research (INSERM, France) and the University College London in England, checked the cholesterol levels of 3,673 participants (26.8 percent women) from the Whitehall II study and gave them memory tests at an average age of 55 and again at 61.

In order to assess participants’ short-term verbal memory the researchers gave them a list of 20 one- or two-syllable words to read aloud at two-second intervals. They then asked study participants to write down as many of the words as they could remember within two minutes.

After observing the data the researchers found that people with more high-density lipoprotein cholesterol did better on memory tests than people had lower levels of HDL. At age 55, participants with low levels of good cholesterol were 27 percent more likely to have memory loss than those with high levels. The memory-robbing condition worsened with time, putting the former group at 53% increased risk of having memory problems by the time they hit age 60.

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

However, the precise mechanism linking HDL cholesterol to dementia remains unclear, the study authors said. "But it is possible that HDL cholesterol prevents formation of beta-amyloid," Singh-Manoux said. "HDL could also affect memory through its influence on atherosclerotic disease and stroke, or vascular injury. Finally, HDL cholesterol may influence memory through its anti-inflammatory and antioxidant effects.”

Drug manufacturers have been working on raising HDL cholesterol since studies showed high levels of HDL cholesterol serves several vital biological functions. Besides protecting against heart disease, the HDL cholesterol helps clear excess cholesterol from the blood, assists nerve-cell synapses to mature and helps control the formation of beta-amyloid, the major component of the protein plaques found in the Alzheimer's patients’ brains.

According to the American Heart Association, one can raise HDL and lower LDL cholesterol by exercising regularly, removing trans fats from the diet, minimizing the intake of all fats, particularly saturated fats, and consuming monounsaturated fats like olive, canola and peanut oils. Statins can also improve HDL and LDL cholesterol levels, when they pose a heart risk.

Cholesterol is a fatty substance made naturally by the body and also found in many foods. HDL cholesterol is opposed to low-density lipoprotein (LDL) cholesterol, which can build up in artery walls, making them hard and narrow. On the other hand, HDL cholesterol takes excess cholesterol back to the liver. That’s the reason why LDL cholesterol is also called “bad” cholesterol.