A new analysis involving more than half a million adults shows that a reduction in low-density lipoprotein (LDL) cholesterol (the “bad” kind) is linked to a substantial decrease in dementia risk, including Alzheimer’s disease.
What’s more, taking statins when you already have optimal LDL cholesterol levels may also protect against dementia, the study found.
“The results support the use of statin therapy within specific LDL ranges for both cardiovascular and cognitive health benefits,” wrote the study author Yerim Kim, MD, a neurologist at Hallym University College of Medicine in Seoul, South Korea, and her colleagues.
Reducing LDL Cholesterol Lowers Dementia Risk — to a Point
The study, published this week in the Journal of Neurology, Neurosurgery & Psychiatry, backs up previous research hinting at brain-protective properties of statins.
Drawing on health data from 11 university hospitals on adults with no previous diagnosis of dementia, scientists identified nearly 200,000 people with LDL levels lower than 70 milligrams per deciliter (mg/dL), and more than 370,000 patients with LDL levels above 130 mg/dL.
- Below 100 mg/dL: optimal
- 100–129 mg/dL: near optimal
- 130–159 mg/dL: borderline high
- 160 mg/dL and above: high or very high
The researchers found that people with LDL levels below 70 mg/dL had a 26 percent lower risk of all-cause dementia and a 28 percent lower risk of Alzheimer’s disease-related dementia than those with LDL levels above 130 mg/dL.
People who already had low levels of cholesterol and were taking statins had an additional 13 percent reduction in all-cause dementia risk and a 12 percent decrease in their risk of Alzheimer’s disease-related dementia compared with people who weren’t taking these drugs.
The researchers noted that the dementia risk benefit faded at very low levels:
- The reduction in dementia and Alzheimer’s risk dropped to 18 percent when LDL fell below 55 mg/dL.
- When LDL levels dropped below 30 mg/dL, the risk reduction disappeared entirely.
The study authors are unsure why this effect wanes at very low LDL levels, indicating that further research is needed.
Study Results Are Enlightening, but Limited
For Christine Cliatt Brown, MD, a behavioral neurologist at the University of Utah’s cognitive disorders clinic in Salt Lake City, the study provides a clearer picture of the association between LDL, statin use, and dementia risk.
She adds, however, that the results are limited in that they are based on observations of preexisting electronic health data and not observational trials.
“Despite the researchers’ efforts, it is also impossible to eliminate confounding variables,” says Dr. Brown, who was not involved in the study. “For example, many people who exercise regularly and follow a healthy diet have lower cholesterol. A healthy diet and exercising regularly reduce the risk of dementia, so this link could potentially exaggerate results.”
Why Statins May Protect the Brain
While this investigation does not explore why statins may protect the brain, Daniel Lackland, DrPH, a neurologist with the Medical University of South Carolina in Charleston and a member of the American Heart Association Stroke Council, points to several mechanisms that may be involved.
- Less inflammation: Statins can lower inflammation, an issue implicated in Alzheimer’s disease and other forms of dementia.
- Improved blood flow in the brain: Statins may enhance blood flow to the brain, potentially improving the delivery of oxygen and nutrients to cells and reducing the chance of damage.
- Slower growth of proteins that harm the brain: Statins may interfere with the growth of amyloid-beta and tau, proteins linked to dementia and Alzheimer’s.
- Reduced heart-disease risk factors: By lowering LDL levels, statins reduce the risk of vascular dementia, a type of dementia linked to cardiovascular disease that leads to impaired blood flow to the brain.
The findings highlight the importance of managing LDL cholesterol as part of an overall dementia prevention strategy, says Dr. Lackland, who was not involved in the study.
He adds, though, that it’s still too soon to recommend statins for people with healthy LDL cholesterol levels.