Sunday, December 6, 2009

Linking High Cholesterol to Alzheimer's Disease

Even modestly elevated cholesterol in midlife portends greater Alzheimer's disease risk in old age, researchers found.

Above average cholesterol of 220 mg/dl or higher at age 40 to 45 raised the risk 31% to 58% for Alzheimer's diagnosis in the next three decades, compared with low cholesterol, Alina Solomon, MD, of the University of Kuopio, Finland, and colleagues reported in the August issue of Dementia & Geriatric Cognitive Disorders.

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These results suggested a lower threshold for risk than some prior studies, the researchers noted.

Cholesterol over 250 mg/dl in middle age elevated Alzheimer's disease risk in the CAIDE study and Finnish cohort of the Seven Countries Study, although it has not been linked over a broader time course in other studies, including the Framingham study.

Rather than waiting to address dementia symptoms as they arise with age, the results support a shift toward earlier attention, the researchers wrote. That means "addressing risk factors as early as midlife, before the underlying disease(s) or the symptoms appear."

Effective management requires a cross-disciplinary approach to lifestyle changes, added co-author Rachel Whitmer, PhD, of Kaiser Permanente in Oakland, Calif.

The researchers analyzed the longitudinal electronic medical record databases of Kaiser Permanente of Northern California. Adults in their mid 40s with even slightly elevated cholesterol (as well as those with high cholesterol) appear to have a greater risk for Alzheimer's disease or related conditions like vascular dementia years later.

Researchers followed over 9,800 northern California residents who were part of the same health insurance plan during the study. The researchers didn't have information on HDL (good) and LDL (bad) cholesterol because these weren't widely understood when the study began in the early 1960s.

Still, if total cholesterol is high, it's logical to assume that levels of the bad cholesterol must also be high since two thirds of the total comes from the LDL (bad) type. The team looked at the total cholesterol levels of participants between 1964 and 1973 when the subjects were between 40-45 years old.

By the end of the research, almost 600 of the subjects had developed either Alzheimer's disease (469 subjects) or a related condition (vascular dementia in 127 subjects) when they were in their 60s, 70s and 80s.

Subjects with total cholesterol in the high range (240 or higher) at the start of the study had a 66% increase in Alzheimer's risk. Borderline high cholesterol (levels between 200-239) brought a 52% increased risk of vascular dementia but no statistically significant risk of Alzheimer's.

This work adds to the growing evidence that controlling your risk factors for heart disease as well as keeping a handle on your weight in midlife can protect the brain as you age. "Keeping your weight down, eating right, and getting regular exercise can keep your heart healthy as you age, and it may also keep your brain sharp," adds lead author Alina Solomon of the University of Kuopio.

Recent estimates have 2.4 to 4.5 million Americans living with the terribly destructive symptoms of Alzheimer's disease, an irreversible and progressive disease that destroys thinking and memory, leaving patients without the ability to do everyday things like cooking, dressing, driving a car, making decisions.

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As yet, science doesn't know what sets off the Alzheimer's process, though experts think the damage starts 10 to 20 years before any mental symptoms appear, and this latest works seems to support the silent progression of this disease. The connection between Alzheimer's disease and cholesterol quite complex. Scientists have learned much of the damage of Alzheimer's comes from deposits of a sticky protein, called beta-amyloid, in vital areas of the brain. As per the latest studies, high cholesterol levels appear to accelerate the formation of beta-amyloid plaques. People with the genetic trait that increases the level of a particular cholesterol transport protein have a greatly increased risk of late-onset Alzheimer's.

While, as stated already, high cholesterol to alzheimer’s link is not scientifically established in all details, there is another indirect proof of the strong connection existence.

It just so happens that we have a perfect example of the problems that can be caused when there is too much cholesterol in the cell. It is Niemann-Pick disease type C, a disease very much like Alzheimer's disease. The cause of Niemann-Pick type C is well understood. It is caused by a genetic defect in one of two proteins, named NPC1 and NPC2. When these proteins are mutated, they lose their ability to transport cholesterol from one point to another inside the cell. Cholesterol then accumulates in the cell. The result is a form of dementia that shares many of the same pathological characteristics of Alzheimer's disease, including tau-containing neurofibrillary tangles and beta-amyloid plaques. Not only that, but mutations in apolipoprotein E, which are a risk factor for Alzheimer's disease, also predispose patients for Niemann-Pick type C. Of course, there are differences between the two diseases as well. But the remarkable similarities of these two diseases illustrate that cholesterol by itself can produce symptoms very similar to those seen in Alzheimer's disease.

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If you have high cholesterol, start by talking to your doctor to get updated cholesterol numbers and learn what you can do to take control of your diet, be more active. Also, if necessary medication can help bring your numbers under control.

Being aware that potentially high cholesterol causes Alzheimer's Disease, as well as following the above actions might not just help your health today, but it may also contribute to your future brain health as well.

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