Research Links Low HDL Levels With Memory Loss
But experts aren't ready to embrace the findings as fact
MONDAY, June 30, 2008 (HealthDay News) -- A new study suggests an association between low levels of "good" HDL cholesterol and loss of memory.
The study, which has followed thousands of British civil servants for decades, found a 27 percent increased loss of memory on a word test for those at age 55 with the lowest HDL levels, compared to those with the highest levels. By age 60, the rate of memory loss had increased to 53 percent, the study found.
"Our results show HDL cholesterol to be important for memory," study author Archana Singh-Manoux said in a prepared statement. "Thus, physicians and patients should be encouraged to monitor levels of HDL cholesterol."
The findings of the study, funded in part by the U.S. government, are published in the July 1 issue of Arteriosclerosis, Thrombosis and Vascular Biology.
The researchers measured HDL cholesterol levels and gave short-term verbal memory tests to 3,673 participants, one quarter of them women, between 1995 and 1997 and again between 2002 and 2004. Participants whose HDL levels decreased during the five years between tests had a 61 percent increased risk of declining ability to remember words, the study found.
No link was found between total cholesterol and other blood fat levels and memory loss. Using statins to lower blood levels of "bad" LDL cholesterol had no effect on memory loss.
In an accompanying editorial, Anatol Kontush, research director at the French National Institute for Health and Medical Research (INSERM), the French equivalent of the U.S. National Institutes of Health, said the study results should be approached with caution.
"At this point I would be very cautious. The biochemistry underlying HDL and brain function is completely unclear," said Kontush.
Conversely, the relationship between HDL and LDL cholesterol levels and cardiovascular disease is clear, he said: LDL deposits can accumulate until they block an artery, while HDL helps keep arteries clear of those deposits.
"In the brain, we are far from that understanding," Kontush said. "We need much more basic information before going in to modify levels."
The most important first step is "just to confirm this observation," Kontush said. Data from such population studies "can lead in completely wrong directions," he said.
The statement by Singh-Manoux, who is a senior research fellow with INSERM and University College London, discussed a possible cause of the relationship seen in the study. HDL cholesterol could affect formation of the amyloid plaque that clogs brains of Alzheimer's patients, she said.
Dr. Ronald Petersen, director of the Alzheimer's Disease Research Center at the Mayo Clinic and vice chair of the Alzheimer's Association's medical and scientific advisory council, was as cautious as Kontush.
"In a general sense, other data are converging to indicate that managing vascular risk factors may be helpful in Alzheimer's disease," Petersen said. "This is supportive of that. But at the same time, we have to be very cautious about whether there is a direct link between HDL and mental function."
You can learn more about good and bad cholesterol from the American Heart Association.