Is high levels of physical activity in early adulthood a risk factor for developing neurodegenerative disorders?

Physical Activity in Early Adulthood and Risk of Neurodegenerative Disorders

High levels of physical activity in early adulthood are not a risk factor for developing neurodegenerative disorders; on the contrary, physical activity appears to be protective against most neurodegenerative conditions, with the possible exception of amyotrophic lateral sclerosis (ALS).

Evidence on Physical Activity and Neurodegenerative Disorders

Protective Effects for Most Neurodegenerative Conditions

Physical activity has been consistently associated with reduced risk for several neurodegenerative disorders:

• A systematic review of 16 prospective studies including over 163,000 participants found that high levels of physical activity were associated with:

  • 28% reduced risk of dementia (RR 0.72,95% CI 0.60-0.86)
  • 45% reduced risk of Alzheimer's disease (RR 0.55,95% CI 0.36-0.84) 1

• Physical activity is recommended as part of prevention strategies for neurodegenerative conditions, with evidence suggesting it can:

  • Improve cognitive functions
  • Reduce the risk of developing dementia
  • Delay progression of existing neurodegenerative diseases 2

Potential Exception: ALS Risk

One important caveat exists regarding amyotrophic lateral sclerosis (ALS):

• A Mendelian randomization study found that genetically predicted increases in moderate-to-vigorous physical activity might increase the risk of ALS in individuals of European ancestry (OR: 2.507,95% CI: 1.218-5.160) 3

• This suggests a potential causal relationship between high-intensity physical activity and ALS risk, though this finding requires further investigation

Mechanisms of Neuroprotection

Physical activity appears to protect brain health through multiple pathways:

1. Vascular health improvements:

   • Regular physical activity slows and may reverse adverse vascular remodeling associated with aging 4
   • Improves vascular homeostasis through increased laminar shear stress

2. Risk factor modification:

   • Reduces traditional cardiovascular risk factors that contribute to neurodegenerative disease
   • Improves insulin sensitivity, reduces blood pressure, and improves lipid profiles 4

3. Direct neurological benefits:

   • May improve brain reserve and cognitive reserve
   • Potentially enhances neuroplasticity and resilience to pathological changes 4

Clinical Recommendations for Physical Activity

The German recommendations for physical activity for adults, which also apply to those with noncommunicable diseases, suggest:

• Moderate-intensity aerobic physical activity for at least 150 min/week OR
• At least 75 min/week of vigorous-intensity aerobic physical activity OR
• A corresponding combination of both intensities
• Additionally, muscle-strengthening activities at least twice a week 4

Special Considerations for Neurodegenerative Conditions

For those already diagnosed with neurodegenerative conditions:

• In Parkinson's disease: Both endurance and resistance exercises may slow disease progression and improve quality of life 4

• In ALS: Limited evidence suggests that endurance and resistance exercises may slow disease progression and improve functionality and quality of life, though caution is warranted 4, 5

Key Takeaways

1. Physical activity in early adulthood is generally associated with reduced risk of most neurodegenerative disorders, particularly dementia and Alzheimer's disease.

2. The potential exception is ALS, where high-intensity physical activity may be associated with increased risk, though this requires further study.

3. Regular physical activity throughout life should be encouraged as part of a comprehensive strategy to reduce the risk of neurodegenerative disorders.

4. For those already diagnosed with neurodegenerative conditions, appropriate physical activity tailored to their condition may help slow progression and improve quality of life.