Bronte Wells
Air pollution is a major environmental problem and a leading cause of morbidity and mortality. It has been linked to various adverse health effects, particularly on the cardiovascular system. There is growing evidence and increasing recognition that air pollution is an emerging risk factor for stroke. Short-term and long-term exposure to air pollution has been associated with an increased risk of stroke, with evidence suggesting that it may trigger cerebrovascular events and increase the likelihood of future occurrences. This link between air pollution and stroke is of significant concern, especially in low- and middle-income countries where air pollution is projected to rise due to rapid industrialization.
| Characteristics | Values |
|---|---|
| Risk factors | High blood pressure, diet low in fruit, obesity, high salt diet, smoking, lack of exercise, air pollution |
| Risk in low- and middle-income countries | Higher risk due to dependence on biomass fuel, firewood, and charcoal for cooking and heating |
| Effect of air pollution on stroke risk | Short-term exposure increases risk of intracerebral haemorrhage, a subtype of haemorrhagic stroke; long-term exposure increases risk of ischaemic stroke |
| Effect of air pollution on the body | Ultrafine particles enter systemic circulation and impact remote sites, promoting atherosclerosis and neuroinflammation |
| Mitigation strategies | Use of public transport, walking, cycling; limiting time outdoors during high pollution; improved domestic ventilation systems |
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What You'll Learn
- Short-term exposure to air pollution increases the risk of intracerebral haemorrhage, a subtype of haemorrhagic stroke
- Long-term exposure to air pollution is linked to ischaemic stroke
- Household air pollution is a risk factor for stroke in low and middle-income countries
- Air pollution is the sixth leading cause of stroke death
- Air pollution increases the risk of stroke by hardening arteries in the brain, making blood thicker and raising blood pressure
Short-term exposure to air pollution increases the risk of intracerebral haemorrhage, a subtype of haemorrhagic stroke
Stroke is a leading cause of disability and the second most common cause of death worldwide. While conventional risk factors for strokes include hypertension, diabetes, sedentary behaviour, and smoking, these do not account for all variations in stroke risk. As such, there is a critical need to identify novel modifiable risk factors for stroke, including environmental agents.
Air pollution is one such environmental agent that has been identified as a risk factor for stroke. Over the past few decades, air pollution levels have continuously increased and are now estimated to be responsible for 14% of all stroke-associated deaths. Evidence from epidemiological studies has demonstrated a strong association between air pollution and cardiovascular diseases, including stroke.
While previous literature has not always distinguished between ischaemic and haemorrhagic strokes, recent studies have found that short-term exposure to air pollution increases the risk of intracerebral haemorrhage, a subtype of haemorrhagic stroke. For example, a Portuguese case-crossover study based on 308 patients with spontaneous intracerebral haemorrhage showed a causative relationship with increased PM2.5 concentration. Similarly, a single-day lag model showed that NO2, NO, NOx, and CO exposure was associated with an increased risk of intracerebral haemorrhage.
The mechanisms by which air pollutants increase the risk of intracerebral haemorrhage are still being investigated. However, it is known that ultrafine particles and nanoparticles can directly translocate across the epithelial border, enter the systemic circulation, and impact remote sites. In the systemic circulation, gaseous pollutants and small particles react with nitric oxide, resulting in reactive oxygen species, which can lead to endothelial dysfunction. Additionally, short-term PM2.5 exposure has been shown to increase markers of plaque vulnerability and systemic inflammation, which are important in the occurrence of acute cerebrovascular disease.
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Long-term exposure to air pollution is linked to ischaemic stroke
Stroke is the second most common cause of death and a leading cause of disability worldwide. It is characterized by acute cerebral blood circulation disorder, caused by artery stenosis, occlusion, or rupture. While conventional risk factors for stroke include hypertension, diabetes, sedentary behavior, and smoking, these do not account for all variations in stroke risk.
There is substantial evidence linking air pollution to cardiovascular diseases, including stroke. Epidemiological studies have demonstrated that both short- and long-term exposure to air pollution increases the risk of stroke. Long-term exposure to air pollution is thought to increase the risk of stroke by hardening arteries in the brain, making blood thicker, and raising blood pressure, thus increasing the risk of clots in the brain. However, the underlying biological mechanisms through which air pollutants exert their effects on the vasculature are still an area of active investigation.
The adverse health effects of air pollution have long been recognized, but the impact of air pollution on the cardiovascular system is less well understood. Air pollution has been identified as a major environmental problem and a risk factor for cardiovascular diseases, with ambient particulate matter (PM) air pollution being a leading cause. Ultrafine particles and nanoparticles in air pollution can directly enter the systemic circulation and impact remote sites. These particles have been shown to upregulate adhesion molecules on endothelial cells, promoting the perivascular migration of monocytes, which is the initiating step of atherosclerosis. There is also growing evidence that some ultrafine particles can directly reach the central nervous system by altering the blood-brain barrier permeability or passing through the olfactory epithelium and olfactory bulb. Once in the brain, these particles may accumulate in areas of vascular inflammation and have direct neurotoxic effects.
The link between stroke risk and whether particles themselves reach the brain remains uncertain. However, evidence suggests that pollutant-related neuroinflammation can combine with vascular insults to increase the risk of ischemic stroke. In most studies, the strongest effects of long-term exposure to pollution were seen on incident ischemic stroke. For example, in the Danish Nurses Cohort, a nationwide sample of over 23,000 nurses, PM2.5 was more strongly associated with incident ischemic stroke than with hemorrhagic stroke. Similar results were seen in pooled samples from Norway and the UK. While the results of studies comparing hemorrhagic and ischemic stroke are not entirely consistent, the effects of long-term exposure to air pollution on ischemic stroke risk are clear.
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Household air pollution is a risk factor for stroke in low and middle-income countries
Stroke is a leading cause of disability and the second most common cause of death worldwide. There is a critical need to identify novel modifiable risk factors for the disease, including environmental agents.
Air pollution has been identified as an emerging risk factor for stroke. Over the past few decades, air pollution levels have continuously increased and are now estimated to be responsible for 14% of all stroke-associated deaths. This figure is even higher in low- and middle-income countries (LMICs), where 99% of deaths attributed to household air pollution occur.
In LMICs, biomass fuel, agriculture-related burning, open fires, and forest burning are more prevalent. In rural communities and deprived populations in urban regions, exposure to household air pollution is intimately linked with poverty due to the dependence on biomass fuel, firewood, and charcoal for cooking and heating with traditional stoves. The increased use of biomass fuel for domestic heating or cooking and poor domestic ventilation systems further contribute to household air pollution in LMICs.
The adverse health effects of air pollution on the cardiovascular system are well-recognized, and there is substantial evidence linking air pollution to cardiovascular diseases, including stroke. Epidemiological studies have demonstrated that both short- and long-term exposure to air pollution increases the risk of stroke. The risk for ischaemic stroke, in particular, increases after short-term (days) and long-term (years) exposure to air pollution. Ultrafine particles and nanoparticles in air pollution can directly enter the systemic circulation and impact remote sites, including the brain, where they may accumulate in areas of vascular inflammation and have direct neurotoxicity.
The association between air pollution and stroke may also be partially ascribed to hypertension and altered vascular resistance, a common risk factor for most cerebrovascular subtypes. Air pollution has been shown to cause short-term elevations in blood pressure, even in young and healthy individuals, and repeated exposure may result in chronic hypertension.
Given the strong association between household air pollution and stroke in LMICs, implementing measures to reduce exposure to air pollutants is essential. This includes promoting the use of clean energy sources, separating living areas from industrial areas, improving domestic ventilation systems, and making public transportation more accessible to reduce polluting road traffic.
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Air pollution is the sixth leading cause of stroke death
Air pollution is a major contributor to strokes, with nearly one-third of the years of healthy life lost to the condition worldwide attributed to it. According to the Global Burden of Disease Study (GBD) in 2016, there were approximately 80.1 million stroke patients and 5.5 million deaths attributed to stroke globally. Stroke is the second most common cause of death worldwide and a leading cause of disability. It is also the second leading cause of death and the third leading cause of serious long-term disability combined.
Air pollution has been linked to an increased risk of stroke, with evidence suggesting that elevated levels of ambient air pollutants can trigger cerebrovascular events in susceptible individuals and increase the risk of future events. Short-term exposure to air pollution can increase the risk of intracerebral haemorrhage, a subtype of haemorrhagic stroke, while the effects of long-term exposure are less clear. However, long-term exposure to air pollution is thought to increase the risk of stroke by hardening arteries in the brain, making the blood thicker, and raising blood pressure, thus increasing the risk of clots in the brain.
The association between air pollution and stroke is particularly strong in low- and middle-income countries (LMICs), where air pollution is projected to rise due to rapid industrialization, urbanization, and the continued use of biomass fuel for cooking and heating. In these countries, household air pollution from burning solid fuels is also a significant contributor to stroke risk. Overall, air pollution is estimated to be responsible for 14% of all stroke-associated deaths, making it the sixth leading cause of stroke death globally during 1990-2017, according to the GBD 2019.
To reduce exposure to air pollutants, individuals can take measures such as commuting by public transportation, cycling, or walking instead of using personal motor vehicles, limiting time spent outdoors during periods of high pollution, and avoiding rush-hour traffic. Individuals with pre-existing cardiorespiratory diseases should be particularly vigilant about reducing their exposure to air pollution due to the increased risk of adverse cardiovascular effects.
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Air pollution increases the risk of stroke by hardening arteries in the brain, making blood thicker and raising blood pressure
Air pollution has been linked to strokes in numerous studies. Over 99% of the world's population lives in areas where pollution levels exceed the World Health Organization's Global Air Quality Guidelines. Ambient air pollution is a leading cause of global stroke incidence, with an annual global incidence of over 15 million patients.
Short-term and long-term exposure to air pollution increases the risk of stroke. Ultrafine particles in the air can enter the bloodstream and promote atherosclerosis, which is the buildup of plaque in the arteries. These particles can also enter the brain and accumulate in areas of vascular inflammation, causing neurotoxicity. This can lead to a higher risk of clots in the brain and stroke.
The risk of stroke due to air pollution is particularly high in low- and middle-income countries (LMICs), where biomass fuel, agricultural burning, open fires, and forest burning are more prevalent. In these countries, the fast-growing economies, urbanization, and industrialization contribute to higher pollution levels and a higher incidence of stroke.
Additionally, traditional risk factors for stroke, such as hypertension, diabetes, sedentary behavior, and smoking, do not account for all variations in stroke risk. Air pollution, especially in the form of fine particulate matter, has emerged as a significant risk factor.
To reduce exposure to air pollutants, individuals can commute by public transportation, cycle, or walk instead of using personal motor vehicles. Limiting time outdoors during highly polluted periods, avoiding rush-hour traffic, and improving domestic ventilation systems can also help mitigate the adverse effects of air pollution on cardiovascular health.
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Frequently asked questions
Yes, there is substantial evidence that air pollution is linked to strokes. It is now considered a major contributor to strokes, with unclean air being blamed for about one-third of the years of healthy life lost to the condition globally.
Sources of air pollution include traffic, factories, power generation, wildfires, and cooking with a wood stove.
Over time, air pollution can harden arteries in the brain, thicken the blood, and raise blood pressure, increasing the risk of blood clots in the brain. It may also have acute effects, such as rupturing plaques that build up in arteries, causing blockages.
Short-term exposure to air pollution can increase the risk of heart attack, stroke, arrhythmias, and heart failure in susceptible people, such as the elderly or those with pre-existing medical conditions.
People can reduce their exposure to air pollution by using public transportation, cycling, or walking instead of driving personal motor vehicles, avoiding busy roads and spending less time outdoors during highly polluted periods.
