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Changing how we see aging

Cholesterol and Our Aging Brain

There might be a reason why the brain produces cholesterol.

Cholesterol is in every cell in our body and becomes concentrated in our brain. Our brain is 60 percent fat, with over 25 percent of that being cholesterol. Most of the cholesterol in the brain is produced in the hypothalamus itself, establishing cholesterol as an integral part of our brain.

One of the most dramatic difference between young and old brains is the reduced myelination—fat sheathing—around nerves, which might explain why aging brains shrink at one percent a year. Myelin is a sheet of lipid, or fat, with the highest cholesterol content of any brain tissue. Even neurotransmitters, the chemical words used in the language that the brain communicates in, are made of cholesterol. George Bartzokis, with UCLA, and his colleagues, found a correlation between diminishing speed of performing tasks and diminishing level of myelination. The older we get, the less myelination we have. And in older age we can destroy this protective layer much faster through excessive alcohol intake and some non-/prescription drugs.

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Myelination seems to be important in how we learn. Although grey matter—on the outside of the cortex made up of neurons—carry messages and does the “thinking”—white matter—the myelinated part of the brain—controls the strength of signals. Myelination is how we learn, strengthening some signals above others. Myelination develops at different ages. Starting from the back of the brain as children, and finishing off at the front of the brain in adulthood. This explains why certain tasks are easier when you are a child then at older ages (learning to speak without an accent.)

And the role of cholesterol seems crucial to this process of myelination. In 2008 Rebecca West and her colleagues from Mount Sinai School of Medicine, New York, unexpectedly found that among normal—no expression of dementia and not having the genes that predispose you to get dementia—older adults aged 85 years and older, high total cholesterol and high LDL (bad) cholesterol were associated with higher memory scores.

Other evidence is mounting. Elizabeth Johnson and Ernst Schaefer with Tufts University, Boston, MA conjectured that one commercially available fish oil capsule per week—180 mg dietary DHA/d—might reduce the risk of dementia by half.  On the negative side, two small trials published in 2000 and 2004 by Matthew Muldoon from the University of Pittsburgh, suggest that prescription medication we use to lower cholesterol—statins—might bring about cognitive decline. He reported that participants taking placebo pills improved on repeated tests of attention and reaction while those on statins did not.  This was further confirmed by anecdotal evidence published in an article in 2003 in Reviews of Therapeutics which reported  that among 60 statin users who had memory problems, when they stopped taking the medication more than half had improved memory.

Science is not truer than religion. Science is being able to challenge the accepted reality of today. It is a method rather than a body of truths. The method is to question beliefs, to test expectations. The problem with science in large U.S. institutions is that it has become a religion.

© USA Copyrighted 2014 Mario D. Garrett

Mario Garrett, Ph.D., is a professor at the school of social work, San Diego State University.

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