High Cholesterol May Increase Dementia Risk, Says New Study

A new study suggests that having too high or too low levels of “good cholesterol” may slightly increase the risk of dementia in older adults.

High-density lipoprotein (HDL) cholesterol, also called “good” cholesterol, absorbs cholesterol in the blood and carries it back to the liver, which then flushes it from the body. Having healthy levels of good cholesterol may help to prevent heart disease and stroke.

However, a new study published in the journal Neurology suggests that abnormal HDL cholesterol levels may increase the risk of dementia, a broad term referring to loss of memory, language, problem-solving, and other thinking abilities.

Researchers analyzed data from 184,367 people with an average age of 70 who did not have dementia at the beginning of the study. The participants filled out a survey on their health behaviors and had their cholesterol levels measured.

The average HDL cholesterol level was 53.7 milligrams per deciliter (mg/dL), while healthy levels are considered to be above 40 mg/dL for men and above 50 mg/dL for women. Based on their HDL cholesterol levels, the participants were divided into five groups.

Over a nine-year follow-up period, 25,214 people developed dementia. Those with the highest HDL cholesterol levels had a 15% higher rate of dementia compared to those in the middle group.

Meanwhile, the lowest levels of good cholesterol were associated with a 7% higher risk of developing dementia, even after adjusting for other risk factors, such as alcohol use, high blood pressure, cardiovascular disease, and diabetes.

“The elevation in dementia risk with both high and low levels of HDL cholesterol was unexpected, but these increases are small, and their clinical significance is uncertain,” said study author Maria Glymour, ScD, of Boston University, in a statement.

The study found no link between LDL cholesterol, sometimes called “bad cholesterol,” and higher dementia risk.

"Our results add to evidence that HDL cholesterol has similarly complex associations with dementia as with heart disease and cancer."

Maria Glymour, ScD

However, the findings may not apply to the general population because the participants were volunteers. Moreover, the study shows an association but not a causal relationship.

Anurag Mehta, director of preventive cardiology at VCU Health Pauley Heart Center, who was not involved in the study, says the findings are not robust enough to recommend managing HDL cholesterol levels for dementia prevention.

“This is an observational study, and randomized clinical trials are needed to answer this question. Moreover, the medicines used to manage HDL cholesterol levels called CETP inhibitors have been studied extensively in the past 2 decades and are seldom used in clinical practice,” he told Healthnews.

High cholesterol and dementia

The link between dementia and cholesterol — both good and bad — is not well understood.

Mehta says that too low or too high HDL cholesterol levels are associated with poor outcomes, especially for coronary artery disease.

“We have known about this relationship with regard to low HDL cholesterol for about six decades, but the relationship of too high HDL cholesterol with cardiovascular risk is something that we have started to appreciate recently,” he says.

A 2023 study published in JAMA Network associated genes related to high HDL cholesterol levels with a higher risk of Alzheimer’s disease, the most common form of dementia.

Another study from 2021 looked at the relationship between bile acids, which are made when the body breaks down cholesterol and dementia. It found that men with reduced bile acid levels are likelier to have higher levels of amyloid proteins in the brain. In Alzheimer’s disease, amyloid sticks together and forms different-sized plaques. The study also linked low bile acid levels to faster brain shrinkage and more damage to the brain’s white matter.

A 2010 study from Sweden with a 32-year follow-up suggests that having higher LDL cholesterol levels in midlife does not increase the risk of Alzheimer’s disease. However, the authors concluded that declining cholesterol levels from midlife to late life could predict Alzheimer’s disease risk.

Managing cholesterol levels

While having high levels of bad cholesterol may not increase the risk of dementia, it can cause peripheral artery disease, high blood pressure, and stroke.

It is important to discuss maintaining healthy cholesterol levels with your healthcare provider. Meanwhile, consider the following lifestyle choices:

• Follow a healthy diet low in saturated and trans fat, salt, and added sugars. Choose foods naturally high in fiber.
• Maintain a healthy weight, as excess body fat affects the body’s ability to remove LDL cholesterol from the blood.
• Exercise regularly. Every week, aim for 2 hours and 30 minutes of moderate-intensity exercise, such as brisk walking or bicycling.
• Quit smoking and limit alcohol intake.

The study suggests that too low or too high cholesterol levels may play a role in developing dementia. However, for now, the recommendations for dementia prevention remain unchanged.