Saturday, November 12, 2011

Weird Connections Between Dementia & Cholesterol

Several prescription medications may help reduce the risk of dementia despite being approved by the FDA as treatments for other conditions. It has been recognized for a number of years that the class of drugs known as statins, which are used to lower cholesterol in the blood, may also decrease the risk of dementia. Because high LDL cholesterol increases the risk of cardiovascular disease, which in turn increases the risk of dementia, these findings were not terribly surprising. About 25 percent of the cholesterol in the body can be found in the brain. Cholesterol is so important to the brain that it does not depend on cholesterol in the blood for its supply. The brain makes its own. There is evidence that increasing the cholesterol burden inside the brain can increase the rate of production of amyloid protein, which in turn exacerbates the deposition of amyloid into the destructive plaques. Studies have shown that statins can reduce the synthesis of cholesterol inside the brain as well as deposition of beta amyloid protein in brain tissue. Thus, beneficial effects of statins could be due in part to decreasing the production of cholesterol in the brain.

Curiously, a study published in one of the most highly regarded medical journals in the world. The Lancet, revealed that statins offered protection from dementia to people regardless of whether they had high or normal cholesterol. Moreover, not all medications that reduce serum cholesterol also reduce the risk of developing dementia. Thus it seems likely that the statins also help prevent dementia through mechanisms that have little or nothing to do with cholesterol. Several different statin drugs have been found to decrease inflammatory responses and oxidative stress in brain. They may also increase brain concentrations of BDNF, which is involved in stimulating nerve growth and neurogenesis. I am obliged to note that, overall, studies using statins to prevent dementia have been rather disappointing. However, this may reflect the complexity of dementia and the fact that many factors play a role in its initiation and progression.