People who regularly inhale smoke from wildfires are more likely to develop dementia, a study suggests.
Researchers at the University of Michigan warned that those who inhaled higher levels of particulate matter, or PM2.5, from wildfires and farms or agricultural production had an up to 13 percent higher risk of developing the disease for every unit increase in the concentrations of the particles. .
PM2.5 are tiny particles invisible to the human eye that are released during fires and the spraying of pesticides and herbicides. These are suspended in the air, where they are inhaled by humans and absorbed into the body, where they can cause inflammation.
Both Hawaii and New York were engulfed in smog from wildfires this year, as experts warn that rising temperatures will only make the fires more common.
The above maps show PM2.5 concentrations in the US for the year 2017 and the sources they came from
The above map shows Alzheimer’s rates by county in the US in the year 2020
The smoky yellow haze enveloped New York City in June (pictured above)
An orange fog covered the whole city
A display of flames as wildfires engulfed the historic town of Lahaina, Maui, Hawaii, on August 9, 2023
About six million Americans have dementia, a number that is expected to continue to rise in the coming years.
The researchers were unable to determine whether the measured pollution caused dementia, but previous studies have suggested that PM2.5 can be absorbed into the blood from the lungs and cause damage to vessels in the brain, increasing the risk of the disease.
Studies in mice have also suggested that pollution may lead to increased production of amyloid beta proteins, which are linked to dementia.
PM2.5 levels in the US have been on a downward trend since 2000 – amid growing awareness and use of cleaner fuel – but remain high in cities and some agricultural areas.
The authorities have set the safe limit for PM2.5 at 12ug/m3. However, this is regularly surpassed in several US cities, including San Francisco, New York and St. Louis. When smog from wildfires in Canada made its way to New York earlier this year, the city was one of the most polluted in the world.
For the study, published today in the journal JAMA Internal Medicineresearchers analyzed data from the Environmental Predictors of Cognitive Health and Aging study – which tracks the environmental exposure of tens of thousands of adults and the cognitive diseases they develop.
They recruited a nationally representative sample of 27,857 people from the study who joined between 1998 and 2016.
All participants were over 50 years old and did not have dementia when they entered the study.
During the decade they were followed, a total of 4,105 participants were diagnosed with dementia — or 14 percent of the participants.
Scientists then compared the spread of dementia cases to levels of PM2.5 in the air in 2017. They also noted the sources of the PM2.5.
In an analysis, controlling for factors such as gender, ethnicity, education and area of residence, they found that agriculture and vehicle exhaust led to the highest increase in the risk of developing dementia.
The largest association was seen for agriculture, where for every increase in PM2.5 levels, the risk of developing dementia increased by 13 percent.
This was followed by wildfire smoke, where it increased by five percent.
People exposed to traffic fumes had an up to six percent higher risk of dementia, while people exposed to smoke from coal-fired power plants had an up to three percent higher risk. But the researchers said this association was not robust.
There was little association between energy from non-coal sources – two percent higher risk – and windblown dust – no increased risk.
This study was observational and could not determine whether exposure to the fumes directly caused dementia.
However, the scientists thought this might be the case. They suggested the particulate matter from afarming can increase the risk of dementia because of the ‘neurotoxic’ pesticides or herbicides used.
They also said that burning natural and synthetic materials could lead to the release of “highly toxic” particles.
The chart above shows how PM2.5 levels across the country have gradually declined over the past two decades
SOUTH AND NORTHWEST: The charts above show PM2.5 levels for two regions of the US over the past two decades
In a secondary analysis, they estimate that pollution could cause up to 188,000 new cases of dementia each year.
Researchers said wildfire smoke was responsible for up to 25 percent of annual average PM2.5 concentrations in the US and up to 50 percent in some western regions.
Dr. Roy Harris, an environmental scientist from the University of Birmingham who was not involved in the study, said: ‘This paper provides useful support for the previous findings in a number of studies that exposure to fine particles (PM2.5) has adverse effects. on cognitive function and may accelerate the onset of dementia.
‘The apparent greater association with particulate matter from agriculture and forest fires is less convincing, with results barely reaching statistical significance.
‘There are important policy implications for identifying those sources or chemical components of particles most associated with the adverse effects.
“However, the scientific work to date does not paint a coherent picture, with many particle sources and components indicted by the various studies.”
Other experts also poured cold water on the findings, saying they showed “barely” a link between pollution sources and dementia.