Washington, July 1 : Low levels of 'good cholesterol' may increase the risk of memory loss and lead to dementia later in life, warns a new study.
The study, led by 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, involved 3,673 participants.
The boffins found that falling levels of HDL cholesterol or 'good' cholesterol were predictors of declining memory by age 60.
"Memory problems are key in the diagnosis of dementia. 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," said Archana Singh-Manoux.
Researchers defined low HDL as less than 40 mg/dL and high HDL as 60 mg/dL or higher.
Researchers measured lipid concentrations in blood samples collected after an eight-hour fast, or at least four hours after a light, fat-free breakfast. They assessed short-term verbal memory using 20 one- or two-syllable words read aloud at two-second intervals. Study participants then had two minutes to write down as many of the words as they could remember.
They found that at the age of 55, participants with low HDL cholesterol showed a 27 percent increased risk of memory loss, and that this risk increased to 53 percent by the age of 60.
Though the precise mechanism linking HDL cholesterol to dementia remains unclear, Singh-Manoux said: "But it is possible that HDL cholesterol prevents formation of beta-amyloid. 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."
"Many previous investigations into the association between lipids and memory in the elderly have focused on total or LDL cholesterol because of their status as proven risk factors for cardiovascular disease," Singh-Manoux said.
"Our results show HDL cholesterol to be important for memory. Thus, physicians and patients should be encouraged to monitor levels of HDL cholesterol."
To raise HDL and lower LDL cholesterol, the American Heart Association recommends exercising regularly; eliminating trans fats from the diet; reducing the intake of all fats, especially saturated fats; and consuming monounsaturated fats, such as olive, canola and peanut oils.
Statins can also improve HDL and LDL cholesterol levels, when they pose a heart risk.
The study and its findings are reported in Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association.