How ‘Good’ Cholesterol May Increase Dementia Risk

How ‘Good’ Cholesterol May Increase Dementia Risk

When doctors talk to older adults about their health, one topic may center around the importance of having “good” cholesterol.” A recent study, however, has added another layer to the discussion after finding that having either high or low levels of “good” cholesterol slightly increases the risk of dementia in older adults.

Health experts say the study, published in October in the journal, Neurology, further supports evidence that maintaining “good” cholesterol levels within a certain range is important for cardiovascular and brain health. 

Cholesterol is a waxy, fat-like substance made by the liver and is essential to good health. The body needs cholesterol to build cells and make hormones, vitamins, and substances that help food to digest. High-density lipoprotein (HDL) is known as “good” cholesterol because it carries cholesterol from other parts of the body back to the liver, and the liver removes the cholesterol from the body.

“The relationship between HDL cholesterol and dementia is more complex than we previously thought,” Erin Ferguson, the study’s lead author and a doctoral student studying epidemiology at the University of California, San Francisco (UC San Francisco) told NBC News. “While the magnitude of this relationship is relatively small, it’s important.”

Although the study results tied HDL cholesterol to dementia, the study does not prove that low or high HDL levels directly cause dementia. 

For the study, the research team from UC San Francisco and Kaiser Permanente analyzed survey data of more than 180,000 people enrolled in the Kaiser Permanente Northern California health plan. The average age of participants was 70. The adults did not have dementia at the start of the study, which was supported by the National Institute on Aging and the National Institutes of Health.

The participants were asked questions about their health behaviors and had their cholesterol levels checked during routine healthcare visits an average of 2.5 times in the following two years. They were then followed within the Kaiser healthcare system for an average of nine years. During that time, 25,214 people developed dementia. 
The research team divided participants into groups based on their HDL cholesterol levels and took into account other dementia risk factors, such as alcohol use, high blood pressure, heart disease, and diabetes. 

The average HDL cholesterol level in the study was 53.7 milligrams per deciliter (mg/dL). Healthy levels are considered to be above 40 mg/dL for men and about 50 mg/dL for women.

Participants whose levels were at least 65 mg/dL were 15 percent more likely to develop dementia, according to the study. The group with the lowest levels—11 to 41 mg/dL—had a seven percent increased risk of dementia, compared to older adults in the middle range of cholesterol levels.

“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,” Maria Glymour, the study’s corresponding author and a professor in the Department of Epidemiology and Biostatistics at UC San Francisco, said in press release.

In contrast, Glymour said no association was found between lipoprotein cholesterol (LDL) and dementia risk among the overall study participants.
LDL is known as “bad” cholesterol because a high level of LDL leads to the buildup of plaque in the arteries.

High Cholesterol Levels Impact the Body

A number of factors, including genetics and diet, play a role in causing high cholesterol levels, which can lead to serious health conditions. For example, high HDL cholesterol levels can cause veins and arteries to stiffen, which can impact the cardiovascular system and increase the risk of stroke. Studies have found that strokes can damage the brain and cause a certain type of dementia known as “vascular dementia.”

Just as high cholesterol levels can affect the cardiovascular system, they can also affect the brain. According to Dr. Yassine, an endocrinologist at the Keck School of Medicine of the University of Southern California, too much HDL cholesterol in the brain can cause inflammation that prompts the brain to produce amyloids, which are abnormal deposits that damage organs and tissues. The accumulation of abnormal deposits of the amyloid protein can lead to Alzheimer’s disease. Dr. Yassine specializes in how changes in lipid metabolism impacts a person’s risk of developing Alzheimer’s.

How to Improve HDL Cholesterol

Health experts recommend that people who are concerned about their HDL cholesterol levels speak with their primary care providers. One way that researchers have found effective is eating healthy foods that can help with improving cholesterol levels. For example, a healthy diet that includes lots of vegetables and fruits, routine exercise, drinking alcohol in moderation, and keeping a healthy weight can lower cholesterol levels.

In contrast, foods with high saturated fats, such as deep-fried foods, baked goods, sweets, and red meats, can raise bad cholesterol levels. Also, lack of physical activity and smoking can cause high levels of cholesterol.

Healthy lifestyle habits help HDL cholesterol transform into HDL particles. This makes it possible for HDL to carry out some of the vital functions for which it is well-known, such as clearing the arteries of LDL cholesterol and transporting it to the liver, where the body eliminates it, Dr. Hussein said.

“The function is really in the particles, not the cholesterol itself,” Dr. Yassine told NBC News. “Simply increasing HDL levels does not increase its function.”

Researchers say HDL cholesterol, as a whole, is a complicated topic that requires further investigation. For example, one study, published in May in JAMA Network, involved genetics and HDL cholesterol. Researchers found that high HDL-cholesterol levels and high systolic blood pressure are associated with a greater risk of Alzheimer’s disease, the most common type of dementia.

Dr. Howard Weintraub, clinical director of the Center for the Prevention of Cardiovascular Disease at NYU Langone Heart in New York, are among those who believe more research is needed in this area. Dr. Weintraub told NBC News that there is not enough evidence saying HDL cholesterol plays a significant role in dementia risk.

Ferguson said their study “might suggest that HDL could be a modifiable risk factor even in late life. But I wouldn’t say that people have to be worried about this just yet.”

Source Links:

https://www.nbcnews.com/health/heart-health/good-hdl-cholesterol-dementia-risk-rcna118772
https://www.bu.edu/sph/news/articles/2023/both-high-and-low-hdl-cholesterol-tied-to-increased-risk-of-dementia/
https://www.medicalnewstoday.com/articles/dementia-after-stroke
https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2805006

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