Can Ambient Fine Particulate Matter (PM2.5) Increase the Risk of Moyamoya Disease?

What is moyamoya disease?

Moyamoya disease is a chronic cerebrovascular disorder.

It is characterized by progressive narrowing and even occlusion of major arteries at the base of the brain. To maintain cerebral blood flow, the body develops numerous small collateral vessels. On cerebral angiography, these vessels resemble a puff of smoke, which gave the disease its name.

As the disease progresses, patients may experience:

• Transient ischemic attack (TIA)
• Ischemic stroke
• Intracranial hemorrhage
• Limb weakness
• Speech impairment
• Headache
• Seizures
• Cognitive decline

Moyamoya disease is relatively more common in East Asia, including China, Japan, and Korea.

What is PM2.5, and why is it receiving so much attention?

PM2.5 refers to fine particulate matter in the air with an aerodynamic diameter of 2.5 micrometers or less.

Because these particles are extremely small, they can:

• Enter the lungs through breathing
• Pass through the alveoli into the bloodstream
• Affect multiple organs throughout the body

Major sources of PM2.5 include:

• Motor vehicle exhaust
• Industrial emissions
• Coal combustion
• Construction dust
• Crop-residue burning
• Forest fires and other sources

Over the past decade, a large body of medical evidence has associated long-term PM2.5 exposure with increased risks of cardiovascular and cerebrovascular conditions such as coronary heart disease, stroke, and hypertension. PM2.5 is therefore considered an important environmental health factor.

Why might PM2.5 affect moyamoya disease?

Current evidence suggests that PM2.5 may not be the sole direct cause of moyamoya disease. During long-term exposure, however, it may exert persistent effects on the cerebral vasculature.

Chronic inflammation

Long-term inhalation of PM2.5 may keep the body in a state of low-grade inflammation. This can irritate the inner lining of blood vessels and interfere with normal vascular function.

Impaired endothelial function

The vascular endothelium is the innermost layer of cells in a blood vessel. It helps regulate blood flow and maintain vascular health. PM2.5 may impair endothelial cell function, making blood vessels more susceptible to abnormal changes.

Increased oxidative stress

Air pollution can increase free-radical levels in the body and cause oxidative cellular injury. Over time, this may promote vascular disease.

Effects on cerebrovascular remodeling

Moyamoya disease itself involves ongoing abnormal remodeling of the cerebral vasculature. Long-term environmental exposures may participate in this process, although the specific mechanisms require further study.

What effects might long-term PM2.5 exposure have?

An analysis of medical data from China reported that:

• The overall incidence of moyamoya disease tended to rise as PM2.5 concentrations increased.
• The relationship was nonlinear rather than a simple straight-line association.
• The increase in disease risk became more apparent once PM2.5 reached higher levels.

These findings suggest that:

People who live for long periods in areas with heavier air pollution may have a higher risk of developing moyamoya disease.

However, the findings do not mean that:

• PM2.5 will inevitably cause moyamoya disease.
• Every person will develop the disease as air pollution levels rise.

The development of moyamoya disease is still influenced by multiple factors, including genetics, age, and an individual's overall health.

Who should pay closer attention to air pollution?

Based on current evidence, groups who should be particularly mindful of the effects of long-term air pollution include:

• People who have lived for a long time in areas with high PM2.5 levels
• People with a family history of moyamoya disease
• People who already have cerebrovascular disease
• People with cardiovascular or cerebrovascular risk factors such as hypertension or diabetes
• People with long-term occupational or environmental exposure to industrial pollution

For patients already diagnosed with moyamoya disease, maintaining good air quality may also form part of routine health management, but it cannot replace standard medical treatment.

How can PM2.5 exposure be reduced in daily life?

Individuals cannot completely avoid air pollution, but they can take steps to reduce exposure.

For example:

• Reduce strenuous outdoor exercise when air quality is poor.
• Monitor the local Air Quality Index (AQI).
• Close doors and windows during severe pollution and use suitable air-cleaning equipment appropriately.
• Wear a standards-compliant particulate respirator when going outdoors.
• Maintain good indoor ventilation and open windows when outdoor air quality is favorable.

These measures are intended to reduce long-term exposure and cannot eliminate risk completely.

How should patients and families interpret these findings?

Members of the general public do not need to become excessively anxious simply because an association has been reported between air pollution and moyamoya disease.

A more appropriate interpretation is:

• Long-term air pollution may be one environmental risk factor for moyamoya disease.
• It may increase disease risk in some people, but it is not the only determining factor.
• Genetics, individual susceptibility, and other environmental factors are also important.

Anyone who develops recurrent brief episodes of limb weakness, language difficulty, transient blurred vision, or other symptoms of cerebral ischemia should seek prompt assessment by a neurologist or neurosurgeon. A clinician should evaluate the symptoms together with imaging findings; air-pollution exposure alone cannot determine whether someone has moyamoya disease.

Frequently asked questions (FAQ)

Does PM2.5 inevitably cause moyamoya disease?

No. Current medical evidence only suggests that long-term exposure to high PM2.5 levels may increase the risk of developing moyamoya disease; it does not establish a direct causal relationship.

Will everyone in a heavily polluted area develop moyamoya disease?

No. Moyamoya disease is multifactorial. Genetic factors, individual differences, and other environmental factors all contribute to disease development.

If I already have moyamoya disease, should I still monitor air quality?

Yes, this is advisable. Although it cannot replace standard treatment, reducing long-term exposure to air pollution may support overall cerebrovascular health.

Can an air purifier prevent moyamoya disease?

There is currently no evidence that air purifiers can prevent moyamoya disease. Their main role is to lower indoor PM2.5 concentrations and reduce exposure to pollution.

How can I tell whether local PM2.5 levels are high?

Check the locally published Air Quality Index (AQI) and PM2.5 monitoring data, and reduce outdoor activity as appropriate during periods of heavy pollution.

Reference

Ning, S., Li, J., & Duan, L. (2026). Correlation analysis between long-term exposure to ambient fine particulate matter and the incidence of moyamoya disease. Chinese Journal of Neurosurgery, 42(6), 555–559. https://doi.org/10.3760/cma.j.cn112050-20260107-00008