Published on: November 20, 2015
by Women’s Brain Health Initiative:
What is Cholesterol?
Cholesterol is a soft waxy substance found in your blood and cells. It is a type of lipid (fat) that comes from two sources; your liver, which makes approximately 80 percent of the cholesterol in your body, and the foods you eat, which are the source of the remaining 20 percent. Cholesterol is transported in your bloodstream in little cholesterol-protein bundles called lipoproteins, namely low-density lipoprotein (LDL) and high-density lipoprotein (HDL).
While cholesterol is often associated with health problems, it is actually a vitally important substance in your body, helping in the production of hormones and vitamin D, for example. LDL cholesterol is needed for cell growth and repair but when too much is in your body it results in plaque buildup in your arteries (known as atherosclerosis), and increased risk of heart disease; that’s why LDL is sometimes referred to as “bad” cholesterol. HDL cholesterol, the one commonly referred to as “good,” helps move LDL cholesterol out of the cells that line your arteries and transport it back to your liver to be excreted. Having a relatively high level of HDL cholesterol appears to be moderately protective against heart disease.
Health problems, including heart and brain diseases, arise when your cholesterol levels get out of whack. Blocked arteries resulting from high LDL-induced atherosclerosis reduce blood flow throughout the body, including to the brain. Your brain contains the most cholesterol of all your organs, 30 percent of your body’s total amount. Cholesterol plays a critical role in your brain, helping to develop and maintain neuronal plasticity and function.
Cholesterol and Dementia
One of the challenges with researching the cholesterol-dementia link is that many people who have unhealthy cholesterol levels also have other conditions that are associated with dementia risk such as high blood pressure and diabetes; it is complex to separate out the factors and determine their individual effects.
The exact relationship between cholesterol and dementia remains a partial mystery, with the limited research that has been done resulting in mixed findings. One finding has been consistent across numerous studies, though: having high total cholesterol in midlife has been found to be significantly associated with a higher risk of dementia. Furthermore, the relationship between cholesterol levels and dementia risk does not appear to remain constant over time; it changes with age. The evidence so far suggests that late-life cholesterol levels are not linked with increased dementia risk and total cholesterol levels decrease as dementia develops.
How to Maintain Healthy Cholesterol Levels
You do not usually experience symptoms when your cholesterol levels are unhealthy, so the only way to know if your blood cholesterol levels are normal is to have regular blood tests. The Heart & Stroke Foundation says that the Canadian guidelines recommend having your cholesterol tested if you:
Since there isn’t a universally “ideal” level for any type of cholesterol, your doctor will consider the various measures obtained in your cholesterol test, as well as your risk factors, medical history and present health when interpreting the results.
If your cholesterol levels are considered unhealthy, your doctor will provide treatment advice that might include lifestyle changes such as: reducing your intake of saturated and trans fats, engaging in regular physical activity, maintaining a healthy body weight, refraining from smoking and limiting alcohol consumption. In some cases, when lifestyle changes prove to be insufficient to keep your cholesterol levels in check, your doctor might prescribe medication.
LATEST RESEARCH FINDINGS ON CHOLESTEROL & BRAIN HEALTH
Research on the relationship between cholesterol and the brain is heading in many interesting directions. Here’s a summary of some of the latest findings:
Unhealthy cholesterol levels may be causing formation of
amyloid plaque in the brain. Research conducted by the University of California Davis Alzheimer’s Disease Center, published in December 2013 in JAMA Neurology, found that unhealthy patterns of cholesterol (i.e., high levels of LDL and low levels of HDL) could be directly causing higher levels of amyloid plaque in the brain, a known hallmark of Alzheimer’s disease. More research is needed to determine exactly how cholesterol is affecting the amyloid deposits in the brain.
Raising HDL cholesterol may lower risk of developing Alzheimer’s disease. A study published in the December 2010 issue of Archives of Neurology by investigators at Columbia University College of Physicians and Surgeons, looked at the link between HDL cholesterol and Alzheimer’s disease among 1,130 elderly Manhattan residents.
They discovered that having low levels of HDL cholesterol (the “good” one) raised participants’ risk of developing Alzheimer’s disease. Previous studies into the relationship between HDL cholesterol and Alzheimer’s disease had inconsistent results, with some finding an association but others finding none. The researchers believe this study may provide a more accurate account of the relationship because it followed subjects for a longer period of time, an average of four years. Though the findings need to be confirmed through further study, this research points to the possibility that increasing your HDL cholesterol level can lower your risk of developing Alzheimer’s disease.
Cholesterol causes cells to divide incorrectly. Researchers at the Linda Crnic Institute for Down Syndrome and the University of Colorado School of Medicine, in a study published in the April 2013 online journal PLOS ONE, found that cholesterol, particularly in the LDL form, caused cells to divide incorrectly and distribute their already duplicated chromosomes unequally to the next generation.
The result was an accumulation of defective cells with the wrong number of chromosomes. Of particular interest was the discovery of cells that carried three copies of chromosome 21, the chromosome that encodes the amyloid peptide that is the key component of amyloid plaque associated with Alzheimer’s disease. Previous studies had shown that up to 10 percent of cells in an Alzheimer’s patient, including neurons in the brain, have three copies of chromosome 21 instead of the usual two. Other research, at Leipzig University, Germany, found that during autopsy 90 percent of the cell death in brains of Alzheimer’s patients was due to the creation and selective loss of neurons with the wrong number of chromosomes. Future research to identify the specific role cholesterol plays in this irregular cell division could lead to completely new therapies for the many human diseases that show signs of defective cell division, including Alzheimer’s disease.
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