A new study suggests an association between low levels
of "good" HDL 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 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 levels 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 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 levels 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."
