An analysis of studies that incorporate data from almost 30 million people has highlighted the role that air pollution, including that comes from car escape emissions, plays in a higher risk of dementia.
It is estimated that dementias such as Alzheimer’s disease affects more than 57.4 million people worldwide, a number that is expected to almost triple 152.8 million cases by 2050. The impacts on people, families and caregivers and society in general are immense.
While there are some indications that the prevalence of dementia is decreasing in Europe and North America, which suggests that it may be possible to reduce the risk of the disease at the population level, in other places, the image is less promising.
Air pollution has recently been identified as a risk factor for dementia, and several studies point to a series of pollutants. However, the force of evidence and the ability to determine a causal effect has been varied.
In an article published on July 24 in Lancet planetary healthA team led by researchers from the Epidemiology Unit of the Medical Research Council (MRC), University of Cambridge, carried out a systematic review and a meta -analysis of existing scientific literature to examine this link. This approach allowed them to gather studies that on their own may not provide sufficient evidence, and that sometimes they do not agree with each other, to provide more general solid conclusions.
In total, the researchers included 51 studies, including data from more than 29 million participants, mainly from high -income countries. Of these, 34 documents were included in the meta -analysis: 15 originated in North America, 10 in Europe, seven in Asia and two in Australia.
The researchers found a positive and statistically significant association between three types of air and dementia pollutants. These were:
- Particles with a diameter of 2.5 microns or less (P.M2.5)A pollutant composed of small particles small enough so that they can be deeply inhaled in the lungs. These particles come from several sources, including vehicle emissions, power plants, industrial processes, firewood stoves and chimneys, and construction dust. They are also formed in the atmosphere due to complex chemical reactions that involve other pollutants such as sulfur dioxide and nitrogen oxides. The particles can remain in the air for a long time and travel very far from where they occurred.
- Nitrogen dioxide (no2)One of the key pollutants that arise from burning fossil fuels. It is found in the escape of the vehicle, especially diesel escape and industrial emissions, as well as those of gas stoves and heater. Exposure to high concentrations of nitrogen dioxide can irritate the respiratory system, worsen and induce conditions such as asthma and reduce lung function.
- Sootof sources such as exhaust emissions of the vehicle and wood on fire. It can catch heat and affect the weather. When inhaled, it can deeply penetrate the lungs, aggravate respiratory diseases and increase the risk of heart problems.
According to the researchers, for every 10 micrograms per cubic meter (μg/m³) of PM2.5The relative risk of an individual would increase by 17%. The average road measurement for PM2.5 In center of London in 2023 it was 10 μg/m³.
For every 10 μg/m3 of no2The relative risk increased by 3%. The average measurement of the road so2 In center of London in 2023 it was 33 µg/m³.
For every 1 μg/m³ soot as is in PM2.5The relative risk increased by 13%. Throughout the United Kingdom, the annual hollin concentrations mediated in selected locations on the road in 2023 were 0.93 μg/m³ in London, 1.51 μg/m³ in Birmingham and 0.65 μg/m³ of Glasgow.
The main author, Dr. Haneen Khreis, of the MRC Epidemiology Unit, said: “Epidemiological evidence plays a crucial role in allowing us to determine whether or not air pollution increases or not the risk of dementia and how much. Our work provides more evidence to support the observation that long -term exposure to external air pollution is a risk factor for the beginning of the dementia in adults previously.
“To address air pollution can deliver long -term health, social, climate and economic benefits. It can reduce the immense load for patients, families and caregivers, while facilitating pressure on overloaded medical care systems.”
Several mechanisms have been proposed to explain how air pollution can cause dementia, mainly that implies inflammation in the brain and oxidative stress (a chemical process in the body that can cause damage to cells, proteins and DNA). Both oxidative stress and inflammation play a well -established role in the beginning and progression of dementia. It is believed that air pollution triggers these processes through direct entry to the brain or through the same mechanisms underlying pulmonary and cardiovascular diseases. Air pollution can also enter the circulation of the lungs and travel to solid organs, starting local and wide inflammation.
The researchers point out that most of the people included in the published studies were white and lived in high -income countries, although marginalized groups tend to have greater exposure to air pollution. Since studies have suggested that reducing exposure to air pollution seems to be more beneficial to reduce the risk of early death for marginalized groups, they ask that future work guarantee a better and more adequate representation in ethnic groups and countries and communities of low and medium income.
The first joint author Clare Rogowski, also from the MRC epidemiology unit, said: “It is likely that efforts to reduce exposure to these key pollutants help reduce the load of dementia over society. It is likely that the strictest limits for several pollutants are necessary for important taxpayers, such as transport sectors and industry. Equitatively.”
A subsequent analysis revealed that although exposure to these pollutants increased the risk of Alzheimer’s disease, the effect seemed stronger for vascular dementia, a type of dementia caused by a blood flow reduced to the brain. It is believed that around 180,000 people in the United Kingdom are affected by this type of dementia. However, since there was only a small number of studies that examined this difference, the researchers did not classify it as statistically significant.
The first joint author Dr. Christiaan Bredell at the University of Cambridge and North West Anglia NHS Foundation Trust said: “These findings underline the need for an interdisciplinary approach for the prevention of dementia. Dementia prevention is not just the responsibility of medical care: this study strengthens the case that urban planning, transport policy and environmental regulation have an environmental regulation important role to play. “
The investigation was financed by the European Research Council of the Horizon 2020 Research and Innovation Program and the Marco Horizon Europe of the European Union.
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