Alzheimer's Risk, Prevention, and Heart Health

Overview

This lecture discusses personal risk for Alzheimer’s and neurodegenerative diseases, key preventive strategies, and major contributors to heart disease and longevity.

Assessing Personal Risk for Alzheimer’s and Dementia

• Ask about detailed family history before genetic testing; family patterns often more informative than single gene tests.
• Identify if dementia is present in family; clarify suspected type and diagnosis details.
• Note age of onset in relatives; early onset (40s–50s) suggests different genetic causes from late onset.

Types of Dementia and Related Neurodegenerative Diseases

• Common forms to ask about in family history:

  • Alzheimer’s dementia
  • Vascular dementia
  • Frontotemporal lobe dementia
  • Lewy body dementia
  • Parkinson’s disease

• Relationship among three major neurodegenerative conditions:

  • Alzheimer’s disease: most cognitively destructive; major impact on memory and thinking.
  • Parkinson’s disease: most movement destructive; primary impact on motor function.
  • Lewy body dementia: combines features of both; impairs movement and cognition.

Genetics of Alzheimer’s Disease

• APOE is the most commonly tested gene; APOE4 is the risk variant.
• Commercial genetic tests mainly capture APOE and a few others; many risk genes not widely tested.
• Family history may reveal unknown or untested genetic contributions.

Early-Onset vs Late-Onset Alzheimer’s Genetics

• Early-onset Alzheimer’s:

  • Onset typically in 40s–50s.
  • Associated with APP, PSEN1, PSEN2 genes.
  • Rare but serious; usually obvious in family history.
  • Less clear how much lifestyle can prevent or delay it.

• Late-onset Alzheimer’s:

  • APOE4 is the most common genetic risk factor.
  • Having two copies of APOE4 (e.g., Chris Hemsworth) greatly increases risk, but is late-onset.
  • About 25% of population has one copy of APOE4.
  • This form is highly amenable to prevention via lifestyle and medical interventions.

Why Knowing Genotype Matters

• Provides motivation to act early (e.g., in 30s) when people feel “indestructible.”
• Guides medical decisions:
  • Choice and intensity of cholesterol-lowering medications.
  • Dosing of omega-3 fatty acids (EPA and DHA).
  • Specific nutrition strategies.
  • Prioritization and prescription of exercise when time-limited.

Major Prophylactic Factors Against Cognitive Decline

• Strongest, least ambiguous protective factors (large “signal” in data):

  • Exercise
  • Lipid (cholesterol) management
  • Avoiding type 2 diabetes
  • Adequate sleep

• These are considered “no regret” moves; benefits are large and well-supported.

Relative Importance

• Among lifestyle levers, exercise likely has the largest impact on long-term health and cognition.
• Dietary impact remains important but may not be as powerful as exercise when comparing effect sizes.

Understanding Hazard Ratios and Relative Risk

• Hazard ratio (HR): statistical measure of relative risk or benefit of an exposure or intervention.
  • HR = 1.0: no difference in risk compared to baseline.
  • HR > 1.0: increased risk (e.g., 1.5 = 50% higher risk).
  • HR < 1.0: decreased risk (e.g., 0.75 = 25% lower risk).

Example Hazard Ratios for Risks and Fitness

• Cardiorespiratory fitness (VO₂ max) and strength drastically outweigh single risk factors like smoking or diabetes when comparing hazard ratios.

• Health is not zero-sum: aim to optimize many factors simultaneously:

  • Normal weight, no diabetes, good sleep, no smoking.
  • High strength and high VO₂ max.

• There is still random bad luck, but goal is to maximize controllable advantages.

Heart Disease: Nature of the Heart and Its Vulnerabilities

• Heart is an efficient, autonomously beating muscle responsive to autonomic nervous system.
• Reacts instantaneously to stressors (startle, altitude, etc.) without conscious control.

Structural Vulnerabilities

• Coronary arteries have:

  • Narrow blood supply channels.
  • Limited ability to revascularize (form new vessels) compared to other muscles.

• Other muscles (e.g., legs) can form collateral blood vessels more easily after small vessel blockages.

• A small dead region in a leg muscle may be unnoticed; the same in the heart (left ventricle) is dangerous.

Atherosclerosis and Evolution

• Atherosclerosis: buildup of plaque in artery walls leading to heart attacks.
• Evolution did not prioritize preventing atherosclerosis because:
  • It mainly affects post-reproductive ages.
  • It did not significantly affect reproductive fitness historically.

Main Drivers of Atherosclerosis

• Smoking

• High blood pressure

• High APOB (apolipoprotein B) levels

• APOB:

  • Protein that wraps around LDL and VLDL particles.
  • Historically may have been beneficial for nutrient transport in scarce environments.
  • Now contributes to cholesterol deposition in artery walls.

• Immune system reaction:

  • Treats cholesterol within artery walls as foreign.
  • Mounts an immune response that contributes to plaque formation and heart attacks.

Preventing Atherosclerosis: Risk Removal and Capacity Building

Removing Main Risks

• Three key modifiable factors:

  • Do not smoke.
  • Maintain blood pressure ≤120/80 mmHg.
  • Maintain APOB at low, physiologic levels (similar to children).

• With these three controlled, progression of atherosclerosis becomes very unlikely.

APOB Testing and Treatment

• APOB measurement:

  • Simple blood test.
  • Relatively low cost (about $12).

• Testing frequency:

  • Example: checked about three times per year in practice.

• If APOB is high:

  • Investigate causes:
    • How much can be changed by diet?
    • How much requires pharmacologic treatment?
  • In most people, reaching truly protective levels requires medications.

• Anti-lipid pharmacotherapy:

  • Considered one of the major victories of modern medicine.
  • Possibly second only to antibiotics as a medical breakthrough.

Improving Heart Health: Protective Strategies

Exercise

• Exercise is a major positive lever for heart health.
• Cardio (aerobic) training:
  • Likely has the greatest direct benefit for the heart.
• Strength training:
  • Still essential for overall health, function, and cognition.
• Approach:
  • Not “cardio or strength”; always “cardio and strength.”
  • Cardio is somewhat more potent for heart-specific outcomes.

Sleep and Stress

• Poor sleep:
  • Harmful to heart health.
  • Likely acts via increased sympathetic activity and cortisol.
• High cortisol:
  • Damaging to coronary arteries.
  • Associated with chronic stress states.

Nutrition and Lipids

• Nutrition can lower lipids, but extreme approaches may cause other issues.

• Example of extreme measure:

  • 10% fat diet:
    • Likely lowers lipids dramatically.
    • Potential downsides: hormonal disruption, reduced muscle mass, other health compromises.

• Trade-off principle:

  • Prefer pharmacology that solves a specific problem without creating new ones.
  • Avoid dietary extremes that fix lipids but introduce multiple new health problems.
  • Use nutrition as part of a balanced, sustainable strategy.

Key Terms & Definitions

• Dementia: Group of conditions with significant cognitive decline affecting daily life.
• Alzheimer’s disease: Neurodegenerative disease causing progressive cognitive impairment; most common dementia.
• Vascular dementia: Cognitive decline due to reduced blood flow to the brain.
• Frontotemporal dementia: Dementia primarily affecting frontal and temporal brain lobes, changing behavior and language.
• Lewy body dementia: Dementia with abnormal protein deposits; causes cognitive and movement symptoms.
• Parkinson’s disease: Neurodegenerative movement disorder; can later involve cognition.
• APOE (Apolipoprotein E): Gene affecting Alzheimer’s risk; APOE4 allele increases late-onset Alzheimer’s risk.
• APP, PSEN1, PSEN2: Genes associated with early-onset familial Alzheimer’s disease.
• APOB (Apolipoprotein B): Structural protein of LDL/VLDL particles; major driver of atherosclerosis when elevated.
• VO₂ max: Maximum oxygen consumption during intense exercise; measure of cardiorespiratory fitness.
• Hazard ratio: Statistical measure of relative risk between two groups over time.
• Atherosclerosis: Plaque buildup in arteries, narrowing vessels and leading to heart attacks and strokes.
• Angiogenesis: Formation of new blood vessels.
• End-stage kidney disease: Severe kidney failure requiring dialysis.
• Sympathetic overtone: Excess activity of sympathetic nervous system; linked to stress responses.
• Hypercortisonemia: Chronically elevated cortisol levels.

Action Items / Next Steps

• Collect detailed family history of dementia and neurodegenerative diseases, including type and age of onset.
• Consider APOE testing when family history suggests elevated risk and patient is ready to act on results.
• Prioritize regular exercise program:
  • Build both cardiorespiratory fitness (VO₂ max) and muscular strength.
• Measure and manage key cardiovascular risks:
  • Check blood pressure regularly and maintain ≤120/80 mmHg.
  • Order APOB blood test and track trends; consider pharmacologic treatment if high.
• Maintain foundational lifestyle habits:
  • Avoid smoking.
  • Prevent or manage type 2 diabetes.
  • Maintain regular, adequate sleep and address chronic stress.
• Use nutrition to support overall health and lipid control, avoiding extreme diets that create new health problems.