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Alzheimer’s disease is a progressive and debilitating form of dementia that causes cognitive decline by destroying neurons and neural connections in the brain. 

As life expectancies increase globally, the prevalence of Alzheimer’s is rising rapidly and it represents a serious public health challenge. 

Understanding the modifiable risk factors for this disease is therefore imperative for developing preventative strategies.

One factor that has long been speculated as potentially contributing to Alzheimer’s risk is high cholesterol levels in the blood. 

The relationship between cholesterol and Alzheimer’s is complex, as cholesterol also has protective functions in the brain and is a building block of neural cell membranes. 

In this article, we examine the latest evidence from clinical trials and studies to determine if high cholesterol should truly be considered a causal risk factor.

But first, let’s understand what Alzheimer’s disease is.

What is Alzheimer’s Disease?

Alzheimer’s disease, a neurodegenerative disorder, is the most common cause of dementia among older adults. 

It gradually erodes cognitive function, impacting memory, thinking, and behavior. 

The disease involves an accumulation of abnormal deposits of beta-amyloid protein forming plaques and twisted strands of tau protein forming tangles inside brain cells. 

Over time, these deposits damage surrounding neurons and synapses in areas involved with learning, memory, and cognition, leading to the death of brain cells and the loss of brain tissue.

Loss of brain volume and neuronal death eventually lead to an inability to communicate and complete basic activities of daily living.

As Alzheimer’s progresses, symptoms will significantly worsen. 

In the final stages, individuals may be unaware of family/friends and need round-the-clock assistance with basic tasks.

While Alzheimer’s is widely believed to stem from a complex interplay of genetic, lifestyle, and environmental factors, the exact mechanisms through which it develops are still under research.

Common signs and symptoms of Alzheimer’s disease include:

  • Memory loss that affects daily life
  • Challenges in planning or solving problems
  • Difficulty completing familiar tasks
  • Confusion with time or place
  • Trouble understanding visual images and spatial relationships
  • New problems with words in speaking or writing
  • Misplacing things and losing the ability to retrace steps
  • Withdrawal from work or social activities
  • Changes in personality and mood, such as depression

While Alzheimer’s is widely believed to stem from a complex interplay of genetic, lifestyle, and environmental factors, the exact mechanisms are still under research. 

Some scientists theorize that certain modifiable risk factors, like high cholesterol levels, may influence the disease process over time.

Understanding Cholesterol

Understanding Cholesterol
Image Credit: medicalnewstoday.com

Cholesterol is a waxy, fat-like substance that is vital for normal cell function in our bodies. 

It helps produce hormones, digest fats, and build cell membranes. 

There are two main types of cholesterol – LDL (low-density lipoprotein) and HDL (high-density lipoprotein). 

LDL, commonly called “bad cholesterol“, carries cholesterol through our bloodstream in a way that builds up plaque in arteries. 

Higher LDL levels increase the risk of heart disease and stroke.

HDL, called “good cholesterol”, acts oppositely by transporting cholesterol from arteries back to the liver for disposal. 

Higher HDL levels help remove excess cholesterol from blood vessels, lowering disease risk.

Our liver produces cholesterol, yet we also obtain it through our diets. 

In addition to dietary intake, genetics influence how much cholesterol our liver produces and how our bodies process it. 

Factors like obesity, lack of exercise, smoking, and diabetes can cause unhealthy imbalances that raise LDL levels.

Other than its crucial roles throughout the body, cholesterol may also play important neuronal functions in the brain. 

It is a structural component of all cell membranes and is essential for repair and maintenance of neural pathways. 

However, excess cholesterol in the brain or problems with transport mechanisms have been hypothesized to potentially contribute to neurodegeneration over time.

Dangers of High Cholesterol

While cholesterol is essential for various bodily functions, an imbalance marked by elevated levels, especially of low-density lipoprotein (LDL) cholesterol, poses significant dangers to health. 

Here are the potential risks associated with high cholesterol:

1. Atherosclerosis: 

Excess LDL cholesterol can accumulate in the arteries, forming plaques that narrow and harden the blood vessels. 

This condition, known as atherosclerosis, restricts blood flow and increases the risk of heart disease and stroke.

2. Coronary Artery Disease (CAD): 

High cholesterol is a major contributor to the development of coronary artery disease, a condition where the blood vessels supplying the heart become narrowed or blocked. 

This can lead to chest pain (angina) and, in severe cases, heart attacks.

3. Peripheral Artery Disease (PAD): 

Elevated cholesterol levels can affect arteries outside the heart, leading to peripheral artery disease. 

This condition reduces blood flow to the limbs, causing pain, and numbness, and potentially leading to tissue damage.

4. Increased Risk of Stroke: 

Atherosclerosis caused by high cholesterol can also impact blood vessels in the brain, increasing the risk of stroke. 

Blockages or ruptures of blood vessels in the brain can result in impaired cognitive function and other neurological complications.

5. Cognitive Implications: 

Some researchers suggest a potential link between cholesterol and an increased risk of Alzheimer’s disease and other forms of dementia. 

Let’s see what recent studies say about this.

Does High Cholesterol Cause Alzheimer’s Disease?

Some evidence suggests there may be a relationship between high cholesterol levels and an increased risk of developing Alzheimer’s disease later in life. 

Cellular and animal studies indicate that hypercholesterolemia contributes to the pathology of Alzheimer’s disease. 

However, research in human populations presents a more nuanced picture where the relationship between these two variables varies across ages.

A recent 17-year study of over 100,000 individuals found that both low and high levels of HDL (“good”) cholesterol were associated with elevated dementia risk compared to mid-range levels. 

However, the association between LDL (“bad”) cholesterol and dementia risk was found to be more modest.

However, not all research supports a direct causal link. 

For example, a large Johns Hopkins-led study found that high cholesterol in mid-life did not increase Alzheimer’s risk for women later on. 

Intriguingly, it did find those whose cholesterol declined from mid-life to old age faced 2.5 times greater dementia risk than those with stable or high levels.

Another study reported that fluctuating total cholesterol within five years, rather than stable high levels, maybe more problematic by raising Alzheimer’s risk by 19%. 

In that study, among nearly 11,700 adults, the greatest variability in cholesterol levels correlated with higher dementia risk.

Interpreting these results is complex, as many with high cholesterol also have comorbid conditions like hypertension, diabetes, or obesity – themselves risk factors for cognitive decline. 

Overall, the evidence suggests fluctuating rather than consistently high cholesterol may confer greater risk. 

More research is still needed to fully understand this relationship across the lifespan.

Old Men
Image Credit: hindustantimes.com

Statins and Alzheimer’s Risk

Statins are commonly prescribed medications that lower LDL cholesterol levels and reduce the risk of cardiovascular events like heart attack and stroke. 

However, some patients hesitantly refuse or stop taking statins due to safety concerns raised in the media about potential adverse cognitive effects, especially in older adults.

While early reports associated statin use with reduced cognition, more rigorous modern studies find no such risk. Research now suggests statins may even decrease Alzheimer’s risk. 

A 2021 meta-analysis of over 20 studies found statin use was linked to a lower risk of both overall dementia and Alzheimer’s disease specifically.

Similarly, a 2023 study found statin users experienced slower cognitive decline over time compared to non-users

Almost all reviewed research recommends statin use for eligible patients.

Statins’ protective effects appear to outweigh their hypothetical risks which are often cited in mass media. 

Therefore, statins should be taken as prescribed to manage cholesterol and potentially support brain health in older age.

Other Ways to Manage Cholesterol

Here are some other ways than statin to manage cholesterol levels:

1. Heart-Healthy Diet

Adopting a Mediterranean-style diet low in saturated and trans fats can help lower LDL cholesterol. 

Focus on whole grains, fruits/veggies, fish, nuts/seeds, and healthy oils, and limit red meat and full-fat dairy.

2. Weight Management and Exercise

Shedding even modest amounts of weight, around 10 lbs for those overweight or obese, can positively impact cholesterol values. 

Aim for at least 150 minutes of moderate activity like walking or swimming per week. 

Exercise helps the liver clear cholesterol from the bloodstream more efficiently.

3. Cholesterol-Lowering Supplements

Natural supplements like plant sterols/stanols, artichoke extract, red yeast rice, and omega-3s may provide modest reductions when added to lifestyle changes. 

4. Quit Smoking

Smoking not only increases cholesterol levels but also doubles the risk of heart disease. 

Quitting smoking promotes swift improvements in cholesterol levels. 

Reducing the Risk of Alzheimer’s

While age and genetics are uncontrollable risk factors for Alzheimer’s, lifestyle choices make a meaningful difference. 

Here are proactive steps to reduce the risk of Alzheimer’s:

1. Regular Exercise:

Exercise not only enhances cardiovascular health but also lowers the risk of conditions linked to dementia. 

Engage in regular physical activity to boost blood flow, improving oxygen and nutrient delivery, including to the brain.

2. Moderate Alcohol Consumption:

Limit alcohol intake to moderate levels. Excessive consumption and binge drinking are associated with cognitive decline over time, making moderation crucial. 

3. Quit Smoking or Avoid Starting:

Smoking accelerates cognitive decline by depleting antioxidants and promoting inflammation and plaque buildup in blood vessels, including those serving the brain. 

Quitting smoking or avoiding it altogether supports brain health.

4. Limit Toxic Exposures:

Minimize exposure to harmful chemicals like asbestos and heavy metals that are implicated in some degenerative brain studies. 

When possible, adopt practices to reduce contact with such substances.

5. Social and Mental Engagement:

Combat loneliness by staying socially engaged. 

Stimulate the mind with puzzles, continuous learning, and socialization, contributing to cognitive reserve against dementia in later life.

6. Manage Chronic Diseases:

Seek medical care for chronic diseases and risk factors, such as diabetes and hypertension. 

Controlling underlying conditions indirectly supports brain health and reduces the risk of cognitive decline.

Conclusion

In conclusion, while the research has produced mixed results, studies tend to suggest that fluctuating cholesterol levels may be more closely correlated with Alzheimer’s risk than stable high levels. 

However, definitive evidence of cholesterol directly causing Alzheimer’s is still lacking due to the complex factors involved. 

Regardless of the exact relationship, maintaining healthy cholesterol is important for overall well-being since high levels are a known risk for cardiovascular and metabolic issues. 

Even if cholesterol does not independently cause Alzheimer’s, controlling it through lifestyle practices remains a prudent approach consistent with brain and body health recommendations. 

FAQ’s:

1. Does the type of fat I eat (saturated, unsaturated, trans) affect my risk differently?

Diets high in saturated and trans fats tend to increase LDL more than unsaturated (like olive oil) fats.
Limiting saturated/trans fats and emphasizing unsaturated fats supports heart and brain health.

2. If high cholesterol doesn’t cause Alzheimer’s, is it still important to manage cholesterol levels?

Absolutely. Regardless of its direct correlation with Alzheimer’s, high cholesterol poses significant risks to overall health, including cardiovascular complications. 

3. Are statins a recommended treatment to prevent Alzheimer’s in individuals with high cholesterol?

Yes, statins are recommended for individuals with high cholesterol, as studies suggest they are associated with a lower risk of dementia and Alzheimer’s.

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