A new study shows that high cholesterol levels are associated with changes in the brain that are characteristic of Alzheimer’s disease. This was done when tissue samples from the brains were examined on autopsy.
Those who had total cholesterol levels over 224 mg/dL before they had any symptoms of Alzheimer’s, were at least seven times more likely to have beta-amyloid plaques in their brains by the time they died. This was compared to people whose cholesterol was under 173 mg/dL.
The American Heart Association considers total cholesterol levels below 200 mg/dL to be desirable.
The "bad" cholesterol" LDL, over 155 mg/dL was also strongly associated with the likelihood of developing beta-amyloid plaques. Compared to those whose LDL was lower than 106 mg/dL. People with high LDL levels were at least eight times more likely to display pathologic features of Alzheimer’s disease.
According to the AHA the ideal LDL levels are felt to fall below 100 mg/dL.
Beta-amyloid is a sticky protein that clogs the brains of people who have Alzheimer’s disease. Although researchers aren’t sure how beta-amyloid is related to the memory loss and other changes that occur with Alzheimer’s. One theory is that plaques that form between nerve cells may jam the brain’s communication network. The study suggests that serum cholesterol in excess of a certain threshold level would trigger the plaque formation. And people who keep their cholesterol down as they age might be able to reduce their risk of plaque formation.
In Alzheimer’s, plaques are usually found in conjunction with another problem called tangles.
Tangles are twisted fibers of tau protein that build up inside nerve cells. It is believed that a buildup of beta-amyloid might cause tangles. That growing numbers of tangles in the brain might lead to Alzheimer’s symptoms. Although, the study found that while cholesterol seemed to be associated with the development of plaques, it did not seem to influence tangles.
Important Questions Remain
Experts who reviewed the study say its findings are valuable, since few studies have been able to connect blood cholesterol levels to physical changes that happen years later in the brain. There’s actually little data on the relationship between cholesterol and Alzheimer’s disease pathology in humans. And there’s little known about the relationship of cholesterol in earlier life to the development of Alzheimer’s disease in later life.
However, there’s a lot of missing pieces in the chain of evidence in this study.
Although scientists have long suspected that cholesterol plays a role in Alzheimer’s disease. It is still not clear what that may be.Studies that tried to treat or prevent Alzheimer’s disease by lowering cholesterol using statin medications have not produced convincing evidence. There’s not even enough evidence to show that plaques in the brain cause Alzheimer’s symptoms.
What is Alzheimer's disease?
It could be that the disease is somehow causing both higher cholesterol levels and plaques in the brain, rather than the other way around. More study needed to be done because no one can really conclude from this study that cholesterol causes Alzheimer’s or that lowering your cholesterol would prevent it!