MY HIGH HDL CHOLESTEROL IS GOOD. MAYBE NOT. A new study shows that high and low levels of high-density lipoprotein cholesterol (HDL-C) — but not levels of low-density lipoprotein cholesterol (LDL-C) are associated with increased dementia risk. Today, we explore the relationship between HDL cholesterol and dementia.
The World Health Organization reports that more than 55 million people have dementia worldwide, with over 60 percent living in low-and middle-income countries. Every year, there are nearly 10 million new cases.
As the population ages, epidemiologists believe the prevalence of dementia will rise, making it essential to understand better the risk factors associated with this condition.
One factor that has gained attention in recent years is high-density lipoprotein (HDL) cholesterol. Many consider HDL cholesterol the “good” cholesterol because it helps remove excess cholesterol from the bloodstream.
I will explore the new study suggesting a relationship between high and low HDL cholesterol levels and the risk of developing dementia.
The Role of HDL Cholesterol
HDL cholesterol is one of the two main types of cholesterol found in the body, with the other being low-density lipoprotein (LDL) cholesterol.
Cholesterol is a waxy, fat-like substance essential for various bodily functions, such as building cell membranes and producing hormones. However, an imbalance in cholesterol levels can lead to health problems.
Many refer to HDL cholesterol as “good” cholesterol because it removes excess cholesterol from the bloodstream.
It acts like a scavenger, picking up excess cholesterol from the arteries and transporting it to the liver, where it is broken down and removed from the body.
This process is known as reverse cholesterol transport and helps to protect against the buildup of cholesterol in the arteries, a major risk factor for heart disease.
The Role of LDL Cholesterol
On the other hand, many refer to LDL cholesterol as “bad” cholesterol because high levels of LDL can lead to the accumulation of cholesterol in the arteries, causing atherosclerosis (the hardening and narrowing of the arteries).
Atherosclerosis is a critical risk factor for heart disease, stroke, and other cardiovascular problems.
Now, let’s explore the links between HDL cholesterol and dementia risk.
New Study Findings: Cholesterol and Dementia Risk
My HDL cholesterol is relatively high. I may have a lower risk of cardiovascular diseases such as heart attack and stroke.
However, a new study adds to growing evidence that low and high HDL cholesterol levels are associated with an increased risk of dementia.
The findings suggest a U-shaped relationship between HDL cholesterol levels and cognitive decline.
Those with the highest HDL cholesterol levels had a 1.15 times higher rate of dementia. Individuals with the lowest levels had a 1.07 times increase in risk compared to older adults in the middle range of cholesterol levels.
In other words, it’s not just low HDL cholesterol that may pose a risk; high levels can be problematic, too.
Study Details
Researchers at the University of California San Francisco and Kaiser Permanente (USA) analyzed survey data from over 184,000 individuals enrolled in the Kaiser health plan.
Subjects had an average age of 70 and did not have dementia at study entry. All answered questions on their health behaviors and had their cholesterol levels checked (during routine healthcare visits) an average of 2.5 times in the following two years.
Investigators followed the study participants for an average of nine years. During that time, 25,214 people developed dementia.
Subjects had an average HDL cholesterol level of 54 milligrams per deciliter (mg/dL). Experts consider health levels over 40 for males and over 50 for females.
The researchers considered other factors affecting dementia risk, including high blood pressure, alcohol use, diabetes, and cardiovascular disease.
Explaining Low HDL Cholesterol and Dementia Risk
Several studies have found that individuals with low HDL cholesterol levels are at a higher risk of developing dementia.
One of the potential mechanisms behind this link is that low HDL cholesterol may be associated with increased inflammation and oxidative stress in the brain, both of which can contribute to the development of neurodegenerative diseases like Alzheimer’s.
Low HDL cholesterol is associated with lower gray matter volume in cognitively healthy adults. Could this change theoretically put them at a higher risk of cognitive decline?
Low HDL cholesterol may also impair the brain’s ability to repair and maintain itself, making it more vulnerable to damage.
Explaining High HDL Cholesterol and Dementia Risk
Surprisingly, high HDL cholesterol levels are also associated with an increased risk of dementia.
While HDL cholesterol is generally considered beneficial for heart health, excessively high levels may adversely affect the brain.
One possible explanation is that very high HDL cholesterol levels indicate an underlying health condition or an imbalance in cholesterol metabolism that affects the brain negatively.
Alternatively, excessive HDL may promote brain inflammation. It may cause neuroinflammation by directly shuttling an endotoxin to the brain.
Endotoxins are toxic substances bound to a bacterial cell wall and released when the bacterium ruptures or disintegrates. Endotoxins consist of lipopolysaccharide and lipoprotein complexes.
The U-shaped Relationship
The U-shaped association between HDL cholesterol and dementia reminds me that maintaining a healthy balance of HDL cholesterol may be important for brain health.
Extremely low or high levels can be detrimental, and the sweet spot lies in between. This balance may help protect against the cognitive decline associated with dementia.
Listen to study lead author Erin Ferguson, an epidemiology doctoral student at the University of California San Francisco:
“The relationship between HDL cholesterol and dementia is more complex than we previously thought. While the magnitude of this relationship is relatively small, it’s important.”
The results show a correlation between HDL cholesterol and dementia but do not prove low or high lipid levels directly cause dementia.
Implications for Brain Health
Maintaining healthy HDL cholesterol levels is essential for reducing the risk of dementia. To do so, here are the things I do:
- A balanced diet. A diet rich in fruits, vegetables, whole grains, and healthy fats can help maintain my cholesterol balance. Omega-3 fatty acids in fish and monounsaturated fats in olive oil can positively impact my HDL cholesterol levels.
- Regular Physical Activity. Exercise is associated with higher HDL cholesterol levels and can help reduce my dementia risk by improving cardiovascular health.
- Smoking Cessation. I don’t smoke. Smoking lowers HDL cholesterol levels and poses numerous other health risks. Quitting smoking can have a positive impact on cholesterol balance and overall health.
- Limiting Alcohol Consumption. Excessive alcohol intake can lead to elevated HDL cholesterol levels, possibly associated with an increased risk of dementia. I know that moderation is key.
- Managing Chronic Conditions. Diabetes and obesity can influence cholesterol levels. If I had either, I would focus on effectively managing these conditions; doing so can be crucial to maintaining overall health and reducing dementia risk.
Conclusions: Cholesterol and Dementia
The link between HDL cholesterol and dementia risk is a complex one.
While many celebrate HDL cholesterol as the “good” cholesterol due to its role in cardiovascular health, the relationship with cognitive function is not as straightforward.
Low HDL cholesterol levels are associated with an increased risk of dementia, possibly due to inflammation, oxidative stress, and impaired brain repair mechanisms.
Surprisingly, very high HDL cholesterol levels may also linked to cognitive decline, possibly indicating underlying health issues.
Final Thoughts on Cholesterol and Dementia
Maintaining a healthy balance of HDL cholesterol is essential for brain health.
A balanced diet, regular physical activity, and lifestyle modifications like quitting smoking and moderating alcohol intake can help achieve this balance.
Effective management of chronic conditions is also critical in reducing dementia risk. What’s good for the heart may also be good for the brain regarding HDL cholesterol.
Finally, I have some questions about the study: Were the upper and lower limits for low and high HDL cholesterol defined before data collection? Or were they refined to give the most statistically significant results?
And this:
The effect size is relatively small. I would conclude that there may be a small association between abnormal HDL cholesterol and dementia, but there is no evidence for this being a therapeutic target.
The clinical significance of the research findings is uncertain. The new study suggests that HDL could be a modifiable risk factor, but I am not worried about my slightly high HDL yet.
Thank you for reading “Cholesterol and Dementia.”
