How we’re polluting our minds

In Australia, we are blessed in many ways, including the quality of the air we breathe every day.

Although we are a fully industrialised country, our air quality ranks among the highest in the world.

The importance of air quality is in some ways obvious. High levels of pollution are known to increase the risk  of respiratory diseases and cancer, for instance, along with heart disease  and strokes.

What is becoming increasingly clear, however, is that air pollution increases the risk of dementia. Such is the strength of the association that the recent Lancet Commission report into modifiable risk factors for dementia placed pollution among its list of 14.

Though it is a complicated topic, one of the types of pollution that seems to be of most concern is fine particulate matter.

This is also known as PM 2.5, denoting its size of 2.5 microns in diameter. To give you an indication of how small this is, the diameter of a strand of human hair is 50 to 70 microns.

So, we’re dealing with tiny particles – ones that are invisible to the naked eye.

The Global Burden of Disease Study goes so far as to say that outdoor PM 2.5 is the most important environmental risk factor for disease in Australia.

These pollutants are small enough to enter the bloodstream through the lungs and ultimately may end up in the brain, causing a cascade of inflammation and oxidative stress which damages and kills off nerve cells. The negative effects of these chemicals on our blood vessels may also explain the increased dementia risk.

Some research has also shown that certain chemicals in the fine particulate matter are found within amyloid plaques in the brain.

Amyloid is thought to have an initial protective effect on the brain and perhaps forms to contain these chemicals in some way. But ultimately, too much amyloid can lead to other processes which further damage the brain and lead to Alzheimer’s dementia.

There are many sources of air pollution, including agriculture, road and other traffic and the burning of coals. Perhaps of specific relevance to Australia, though, and especially as another scorching summer beckons, are wildfires.

If you are doubtful of the link between wildfire smoke and the disorder, a study recently reported at a leading dementia conference might convince you otherwise.

This study evaluated more than a million people in southern California (another area of the world frequently beset by wildfires) over a decade and concluded that the risk of dementia from wildfire smoke was greater than the risk conferred by other sources of fine particulate matter.

Another study that supports the link between pollution and dementia is one from 2016. In this case, 6.6 million people living in Ontario, Canada, were examined and it was found that those living within 50m of a major road were seven per cent more likely to develop dementia than those living more than 300m away.

Now, of course, it is impossible to avoid all pollution (and it’s not easy for those who live next to major highways to simply relocate) but there is some evidence that wearing certain face masks can reduce the exposure to PM 2.5.

Air-conditioning with a high-efficiency particulate air filter can also be helpful when there is air pollution outside of the home. Staying indoors when there is a risk of bushfire smoke inhalation also seems prudent if practical and safe.

It seems that impacts from the modern world (traffic and industrialisation) and time immemorial (bushfires have been around a long time!) can be detrimental and create another factor to consider when trying to optimise brain health.

 Kailas Roberts is a psychogeriatrician and author of Mind Your Brain: The Essential Australian Guide to Dementia, available at bookstores and online. Visit yourbraininmind.com or uqp.com.au