Does Air Pollution Cause Alzheimer’s Disease?

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Written by Consensus
6 min read

Does air pollution cause Alzheimer’s disease?

Check out this answer from Consensus:

The collective evidence from multiple studies strongly suggests that exposure to air pollution, particularly fine particulate matter (PM2.5), nitrogen dioxide (NO2), and ozone (O3), is associated with an increased risk of Alzheimer’s disease and other forms of dementia. The mechanisms likely involve oxidative stress, inflammation, and epigenetic changes. These findings underscore the importance of addressing air quality as a public health measure to potentially reduce the incidence of neurodegenerative diseases.

The relationship between air pollution and Alzheimer’s disease (AD) has garnered significant attention in recent years. Various studies have explored how exposure to different air pollutants may contribute to the onset and progression of AD, as well as other forms of dementia.

Key Insights

  • General Association Between Air Pollution and AD:
    • Multiple studies indicate a positive association between exposure to air pollution and an increased risk of Alzheimer’s disease and dementia        .
  • Specific Pollutants and AD Risk:
    • Particulate Matter (PM2.5 and PM10): Higher levels of PM2.5 and PM10 are consistently associated with an increased risk of AD and cognitive decline       .
    • Nitrogen Dioxide (NO2) and Nitrous Oxides (NOx): Greater exposure to NO2 and NOx is linked to a higher risk of dementia and AD   .
    • Ozone (O3): Long-term exposure to elevated levels of ozone is associated with an increased risk of developing AD .
  • Mechanisms of Neurotoxicity:
    • Studies suggest that air pollutants may mediate neurotoxicity through mechanisms such as amyloid-beta processing, oxidative stress, and inflammation .
    • Epigenetic changes, including reduced repressive histone modifications and increased DNA damage, have been observed in individuals exposed to high levels of particulate air pollution.
  • Biomarkers and Cognitive Decline:
    • Higher exposure to air pollutants is associated with increased levels of AD biomarkers, such as amyloid-beta deposition and neurofilament light (NfL) in cerebrospinal fluid.
  • Geographical and Population Variability:
    • The risk of AD due to air pollution is notably higher in heavily polluted regions compared to lightly polluted areas.
    • Studies from various countries, including the USA, Canada, Taiwan, Sweden, and the UK, show consistent findings despite differences in methodology and population selection  .

 

 

Does air pollution cause Alzheimer’s disease?

Ying Zhang has answered Likely

An expert from University of Sydney in Epidemiology, Environmental Science

Severe air pollution can cause many health problems. It may not be a direct cause of Alzheimer’s disease but a epidemiological risk factor that could contribute to the development of the disease.

 

Does air pollution cause Alzheimer’s disease?

Eirini Dimakakou has answered Near Certain

An expert from Heriot Watt University in Epidemiology, Biostatistics

Exposure to air pollution is a particular concern to the public. In Britain, the 1952 ‘London Smog’ heightened public awareness of the problem because of the increased mortality and morbidity reported soon after the event. It is now widely accepted that exposure to air pollution may cause or exacerbate allergic respiratory diseases (e.g., asthma), chronic obstructive pulmonary disease, pneumonia, lung cancer and cardiovascular disease. More recently, evidence has emerged from epidemiological and experimental laboratory studies that long-term exposure to particulate air pollution may be associated with dementia.

Particulate matter (PM), also known as particulate air pollution, is a complex mixture of extremely small particles and liquid droplets that are in the air of our cities. Once these particles are inhaled, they can cause serious health effects. Particles that are very small in diameter cause the greatest problems, because they can get very deep into the lungs, and they may even get into the bloodstream or the brain. Particulate matter comes from both human and natural sources. Soot from diesel vehicles, smoke from fires and wind-blown dust are all sources of airborne particulate matter.

Both environmental and genetic factors play a crucial role in the causation of dementia and the underlying neurodegenerative diseases, such as Alzheimer’s disease. As the world’s population is ageing, dementia has become a major public health concern. Most cases of neurodegenerative diseases are sporadic, and so identification of air pollution as an important environmental risk factor may help us better understand the aetiology of these diseases.

Human epidemiological evidence suggests that long-term exposure to fine particulate air pollution may be a risk factor for neurodegenerative diseases. The mechanisms underlying this are currently unknown, but it may involve the particles moving from the inhaled air to the brain or the release of inflammatory chemicals from the lung, which may indirectly cause damage in the brain. It is already known that particles in air pollution stimulate inflammatory and other harmful responses in the lung. Inflammation and oxidative stress are also implicated in the pathogenesis of dementia and thus the capacity of air pollution to stimulate such responses may contribute to the pathogenesis of dementia. 

It is not absolutely clear whether particulate air pollution causes dementia, although exposure to air pollution may contribute to the initiation of disease or accelerate disease development. Is particulate air pollution an important cause or just another cause?  It’s known that small air pollution particles can enter the brain and the research shows a fairly consistent evidence of a link between air pollution and neurodegenerative diseases, but just not quite sufficient to provide unequivocal scientific proof. There are so many questions still unanswered, which definitely suggests a need for further research in this field.

 

Does air pollution cause Alzheimer’s disease?

Tim Wilkinson has answered Likely

An expert from Edinburgh University in Neurology, Alzheimer’s Disease, Cognitive Science, Epidemiology

There is an increasing body of evidence that links air pollution with dementia.

A review of the area has recently been published: Russ et al. Curr Opin Psychiatry 2019 Mar;32(2):97-104 2019 (https://www.ncbi.nlm.nih.gov/pubmed/30543549)

The authors provide a helpful overview of the field, by reviewing recent studies on this topic. They conclude that:

  • There is now ample evidence that links air pollution to poor brain health
  • We don’t understand when in the life course air pollution has the most impact (i.e. is it worse if exposed to air pollution in childhood, midlife etc)
  • We don’t understand whether it affects one particular subtype of dementia (e.g. Alzheimer’s disease, vascular dementia) compared to others.

 

Does air pollution cause Alzheimer’s disease?

Tia Louise Cummins has answered Extremely Unlikely

An expert from Florey Institute of Neuroscience and Mental Health in Neuroscience, Psychology

Scientists are still unsure of the exact cause(s) of alzheimer’s, however it is likely that a number of factors are involved. Air pollution may be associated with alzheimer’s, but it is unlikely that it is the “cause”. Many lifestyle and medical variables are associated with alzheimers, but we can not deduce the finite cause just yet.

 

Does air pollution cause Alzheimer’s disease?

Paul Ernsberger has answered Likely

An expert from Case Western Reserve University in Pharmacology, Nutrition, Cardiology, Nephrology, Endocrinology, Obesity

Very small particles can enter the blood stream within the aveloi of the lung. From there they can reach the brain and other organs. Rates of lung, heart and neurological diseases can be linked to exposure to fine particulates smaller than 2.5 microns in diameter.

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