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Anthea Rowan

This is the 49th instalment in a series on dementia, including the research into its causes and treatment, advice for carers, and stories of hope.
Clean air is fundamental to health.
Yet the World Health Organization estimates that 99 per cent of the global population live in areas where the pollution exceeds its air quality guidelines.
Pollutants include carbon monoxide, dioxides such as nitrogen dioxide and sulphur dioxide – common by-products of burning fossil fuels – and ozone, caused by a reaction between gases and sunlight.

What is more, it estimates that air pollution is responsible for 7 million deaths annually around the world, and countless lost years of good health.
Pollution causes more than asthma and respiratory diseases. It may also have a contributing role in stroke, heart disease, lung cancer – even our mental health.
It is increasingly clear that air pollution is bad for our brains, too. So bad, in fact, that it is included among 14 modifiable risk factors identified in the 2024 update of the Lancet Commission on Dementia, which estimates that air pollution accounts for one in 43 dementia cases.
The suspicion that air pollution is bad for cognition is not new – there have been lots of studies – but one of the earliest was in dogs.
In the 1990s, residents of Mexico City – then among the most polluted cities in the world – began to worry when their dogs started to behave oddly. Some dogs stopped responding to their owners.
This spurred toxicologist and neuropathologist Lilian Calderón-Garcidueñas to undertake a study that examined brain tissue from 40 dogs that had lived in the city, and 40 dogs from rural areas.
It found that the nasal passages of the city dogs showed signs of damage – and their brains showed signs of neurodegeneration. The dogs from the countryside did not have these signs.

Dogs’ noses are much more sophisticated than human ones. A dog’s sense of smell is thought to be up to 100,000 times sharper than a human’s because they have many more scent receptors than us – for every one of ours, a dog has 50.
Subsequently, Calderón-Garcidueñas examined the brains of humans from the same polluted city and found they also showed signs of damage.
Now a team at the UK’s Francis Crick Institute, a biomedical research centre in London, aims to advance current understanding of how neurodegeneration begins, and the environmental exposures that contribute to it, with its study called “Role of Air Pollution in Dementia” (Rapid).
The researchers behind it, Charles Swanton and Sonia Gandhi, are exploring how air pollution affects our brains by focusing on whether it causes inflammation that leads to neurodegeneration, and whether it affects the build-up of insoluble proteins – amyloid plaques and tau tangles – that are thought to be linked to dementia.
A paper published in April in the Alzheimer’s and Dementia Journal by researchers from Emory University in Atlanta, Georgia, concluded that air pollution may trigger DNA modifications tied to Alzheimer’s disease.

A 2023 Harvard University study that tracked global data found that exposure to high levels of nitrogen dioxide and PM2.5 particles was associated with higher rates of dementia.
PM2.5 particles are very fine, about 3 per cent the width of a human hair. Because they are so fine, and light, they remain airborne for a time, and are easy to breathe in.
They can get into the lungs and bloodstream and once there, they can cross the blood-brain barrier.
These tiny particles are found in vehicle exhausts, factory fumes, wood-burning stoves and many other sources. People in cities, on busy roads, even near airports, are at greater risk because of these particles.
On the flip side, there is evidence that people living in areas with less air pollution are less likely to develop the symptoms of cognitive decline and dementia.
According to Alzheimer’s Research UK, this has been shown in countries such as China, where a clean air act to reduce air pollution was linked to a reduction in older adults struggling with cognitive impairment.
A study that examined this, published in Lancet Healthy Longevity in 2022, concluded that implementing stringent clean-air policies might mitigate the risk of cognitive ageing associated with air pollution.

Busy cities are taking note. In Beijing, the Green Traveller Platform has been introduced which connects devices to track users’ emission-reducing behaviours and reward them with credits that can be exchanged for cash.
London has established Ultra Low Emission Zones. The most polluting vehicles must pay a daily charge to drive in these areas.
Barcelona, in Spain, has introduced “super blocks” (car-free streets); and Bogota, in Colombia, is upgrading its bicycle network.
How to reduce your exposure to air pollution

If you smoke, quit.


Avoid smoke of all kinds – including from smokers, unventilated wood fires and wildfires.


If you are in an area that monitors air pollution, minimise outdoor exposure on days when pollution is high. Close car windows in traffic, and do not let your engine idle if you can turn it off.


When cooking indoors, ventilate however you can, using the oven hood fan and opening windows.


Consider installing a HEPA filter air purifier for your home.


Minimise the use of indoor incense – a hidden source of PM 2.5 – and scented candles.

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How air pollution increases dementia risk and ways to limit your exposure

Wellness

Visibility is reduced as haze affects Hong Kong today, Central.  
30DEC23 SCMP/ Dickson Lee

Air pollution has been linked to dementia, so taking measures such as installing a home air filter may help safeguard your mental and physical health. Photo: Shutterstock

Air pollution over Beijing in 2015. China has introduced a number of laws to clean up its air, which have been linked to a reduction in cognitive impairment in older adults. Photo: Shutterstock

A study of brain tissue of dogs in heavily polluted Mexico City revealed signs of neurodegeneration that were not evident in brain tissue from dogs from rural areas. Photo: Shutterstock

To minimise vehicle use – and emissions – London has established Ultra Low Emission Zones. The most polluting vehicles must pay a daily charge to drive in these areas. Photo: Shutterstock

Avoid burning incense indoors, because it is a source of PM2.5 air pollution. Photo: SCMP

Early signs of dementia, from falls to personality changes and driving difficulties

A driver with cognitive impairment such as Alzheimer’s disease can get lost, react too quickly or too slowly, or - worst case - have an accident. Photo: Shutterstock

Falls can be another early warning sign of the onset of dementia. Photo: Shutterstock

Dr Antonio Terracciano is a professor in the department of geriatrics at Florida State University in the United States. Photo: Florida State University

Dr Alexander Ordoobadi of Harvard Medical School’s Brigham and Women’s Hospital. Photo: Brigham and Women’s Hospital 

“Detrimental personality change” can be noticeable before a diagnosis of cognitive impairment. Photo: Shutterstock

How eating a plant-based diet benefits the environment, the planet and your health

Katia Demekhina, a Hong Kong-based nutritional therapist, says that as well as being good for the environment, plant-based diets can also aid in weight management because they are typically lower in calorie density yet rich in nutrients. Photo: Katia Demekhina

Animal farming practices cause almost double the greenhouse gas emissions compared to plant-based farming, says Tami Best, a functional and integrative dietitian. Photo: Tami Best

Animal farming practices are a primary contributor to greenhouse gas emissions. Photo: Shutterstock

Diets rich in fruits, vegetables, legumes and whole grains can lower the risk of chronic diseases, including heart disease, diabetes and certain cancers. Photo: Shutterstock

Healthy fats are essential for nutrient absorption and overall health. Good plant-based sources include avocados, nuts, seeds and olive oil. Photo: Shutterstock 

Plant-based diets often aid in weight management because they are typically lower in calorie density, yet rich in nutrients, says Katia Demekhina, a Hong Kong-based nutritional therapist. Photo: Katia Demekhina

Why Hong Kong is ideal for open water swimming, a sport which does the mind and body good

Edie Hu, left, on an early morning outing with fellow swimmer Janis Mok. 
Photo: Instagram/edieswimshongkong/

Edie Hu is an open water swimming sensation. She describes how group open water swimming is great for health and why Hong Kong is the perfect place for it. Photo: Amy Miao

Open water swimmer Edie Hu says discovering the sport changed her life. Photo: Edie Hu

Members of Southside Swimming Hong Kong at Repulse Bay. The group has about 3,100 members on Facebook. Photo: Edie Hu

Hu, left, on an early morning outing with fellow swimmer Janis Mok. Photo:Instagram/@edieswimshongkong

Hong Kong-based psychologist and triathlete Olivier Courret can attest to the many benefits of open water swimming for mental health. Photo: Olivier Courret 

Courret poses with the Open Water Swimmers of Hong Kong members in Repulse Bay. Photo: Olivier Courret

Hu is turning 50 in 2025 and hopes to mark the occasion with a 50km swim.

Lifestyle

Health & Wellness

Health

Lists

Decoding dementia

How caring for a parent with dementia taught me about symptoms, prevention and why seeking out the latest research is so important

Author Anthea Rowan (right) with her mother.

Author Anthea Rowan (right) with her mother, who has Alzheimer’s disease, the most common type of dementia. Photo: Anthea Rowan

Anthea with her mother. Photo: Anthea Rowan

Studies suggest that regular exercise lowers the risk of cognitive decline by 35 per cent. Photo: Getty Images

Staying active can help prevent or delay the onset of dementia, studies suggest. Photo: Shutterstock

Why should you have a brain scan to test for dementia when there’s no cure? Knowing can help you delay its onset, neurologist says

It can be daunting to get a brain scan to test for signs of dementia, but a neurologist behind new research reveals the advantages of knowing early. Photo: Shutterstock

New research has found that dementia can be detected as early as nine years before symptoms manifest, and this could have significant implications for treatment. Photo: Shutterstock

Timothy Rittman, the neurologist who led the dementia research at Cambridge University. Photo: Cambridge University

A brain scan showing signs of dementia. Photo: Getty Images

Lizzie Perry, founder of This is Dementia, with her father, who was diagnosed with the disease at 58. Photo: This is Dementia

The approval in the US of a new drug that slows the onset of Alzheimer’s makes Rittman hopeful about the future of dementia treatment. Photo: Cambridge University

Why women are more likely to have dementia than men as they age, and how exercise and engagement can help lower your risk

Women may be at a greater risk of developing Alzheimer’s than men for a number of reasons: biological, societal or cultural. Experts suggest exercise and social engagement can help offset the risk. Photo: Getty Images

The spread of tau – the protein that clumps into the telltale tangles of dementia – may contribute to Alzheimer’s disease. Photo: Shutterstock

Female twins with a male co-twin were less likely to be diagnosed with dementia than female twins with a female co-twin. Photo: Shutterstock

Prenatal care and monitoring pregnant women’s health is key, as it may impact cognition and dementia risk in later life. Photo: Shutterstock

Taking regular exercise is key for women – and men – to reduce the risk of dementia. Photo: Shutterstock

How high or low blood pressure increases the risk of dementia, and why it’s never too late, or early, to adopt a healthy lifestyle to manage it

Having blood pressure that is too high or too low has been linked to a higher risk of dementia, but it’s never too late to start living a healthy lifestyle that will help maintain optimal blood pressure. Photo: Shutterstock


An optimal blood pressure reading, easily measured with a home device, is around 120/80. Photo: Shutterstock

Dr Ruth Peters was lead author of a study looking at the links between blood pressure and dementia. Photo: Dr Ruth Peters

It’s never too late, or too early, to start thinking about brain health and living a healthy lifestyle. Photo: Shutterstock

Problems with reasoning, planning, judgment, memory and other thought processes may result from damage caused by impaired blood flow to the brain – which may be brought on by high blood pressure. Photo: Shutterstock

6 dementia fighting tips from Dr Sanjay Gupta and Marc Milstein, experts on brain health – walk, talk, read, learn, relax, and eat and drink properly

We can protect ourselves against the risk of dementia with some simple lifestyle practices. Exercising (above), eating a good diet, drinking less alcohol, socialising, reading more and trying new things all help keep the brain sharp, say brain experts including Dr Sanjay Gupta. Photo: Shutterstock 

The cover of one of Dr Sanjay Gupta’s book. Photo: Simon & Schuster

The cover of Marc Milstein’s book. Photo: Marc Milstein

Drink alcohol mindfully and ask yourself why you are having that drink. Photo: Shutterstock

Learning new things creates new brain cell connections and helps keep your mind sharp. Photo: Shutterstock

Reading is good for brain health. Try to read a wide range of book styles, and join a book club to discuss with others what you are reading. Photo: Shutterstock

During sleep, our brains are restored and repaired, so relaxing is important if we’re going to get those seven hours of quality sleep. Photo: Shutterstock

Relationships keep us engaged, interested and interesting, and may help prevent dementia. Photo: Shutterstock

‘Like a light switch’: how sundowning syndrome affects dementia sufferers – and their carers; what it is and tips for how to cope

A person with dementia may experience “sundowning” syndrome - towards the end of the day they become more agitated, confused, panicked, resistant to instruction and restless. This affects their carers, too. Photo: Shutterstock

A person in bed, unable to sleep. Conservative estimates suggest about 20 per cent of dementia patients experience sundowning at some point.

Trey Todd is a neuroscientist at the University of Wyoming. Photo: Trey Todd

Sundowning was coined in 1987 by Lois Evans of Penn Nursing at Pennsylvania University. Photo: University of Pennsylvania

The pineal gland in our brain produces melatonin, which is what helps prompt us to sleep and awaken. In a broken system it is disrupted. Melatonin supplements might help fight sundowning. Photo: Shutterstock

Taking a patient with sundowning syndrome for a walk at a consistent time each day, morning or evening, may alleviate symptoms. Photo: Shutterstock

Getting out into the daylight early in the day is good for our sleep patterns, whether we have dementia or not. Photo: Shutterstock

Healthy marriage, healthy mind? Dementia risk lower for people married a long time, studies show; expert suggests why

Research suggests that people who have stayed married for a long time have a lower risk for dementia because they feel less lonely, are more likely to eat well and exercise more, and are more cognitively engaged. Photo: Shutterstock

Vegard Skirbekk is a researcher at the Norwegian Institute of Public Health. Photo: Norwegian Institute of Public Health

Anthea Rowan’s parents on their wedding day. Photo: courtesy of Anthea Rowan

A long-time married partner represents a security that provides a buffer against stressors. Photo: Shutterstock

Anthea Rowan and her husband on their wedding day. Photo: courtesy of Anthea Rowan

If you live with a partner long term, you are more likely to develop healthy daily patterns, to eat well and exercise more. Photo: Shutterstock

‘Dementia village’ that’s the first of its kind helps residents live normal lives, has a restaurant, theatre and supermarket – and no one wears a white coat

Residents are free to live their lives as they like at the world’s first “dementia village”, The Hogeweyk in The Netherlands. Photo: The Hogeweyk

The Hogeweyk, a “dementia villlage” in the Netherlands, provides care and a familiar and safe environment in which people with dementia live while retaining their own identity and autonomy as much as possible. Photo: The Hogeweyk

Jannette Spiering is the senior managing adviser and co-founder at The Hogeweyk in the Netherlands, which offers “humanising care for people with dementia”. Photo: The Hogeweyk

Residents relax around the fountain in the theatre square at The Hogeweyk. Photo: The Hogeweyk 

Residents of The Hogeweyk respond positively to their increased autonomy. Photo: The Hogeweyk

Residents at the healthcare facility take part in a painting class. Photo: The Hogeweyk

Hearing loss dramatically raises the risk of dementia, so why are so many people in midlife doing nothing to prevent it? A test is easy to arrange

Hearing loss has been linked to a higher risk of dementia and cognitive decline,  say experts, who recommend testing for preventable hearing problems (above).  Photo: Getty Images

Alison Huang, a senior research associate at the Cochlear Centre at Johns Hopkins, in the US, says hearing loss makes the brain work harder to process sounds. Photo: Johns Hopkins

Jiang Fan from the School of Public Health at China’s Shandong University. Photo: Shandong University

Checking your hearing in midlife is crucial, and can help you stave off cognitive deterioration. Photo: Shutterstock

Can HRT reduce dementia risk? New hormone replacement therapy studies say yes, upending 2002 reports

HRT use has been linked to better cognition, blood flow and brain size and a reduction in all neurodegenerative disease in recent studies. Photo: Shutterstock

HRT (hormone replacement therapy) use has been linked to better cognition, blood flow and brain size and a reduction in dementia and other neurodegenerative disease in recent studies. Photo: Shutterstock

If HRT is started after the age of 65, brain cells will have already been deprived of oestrogen for many years. This could mean there is a decline in neuronal connections – the brain’s messaging system. Photo: Shutterstock

HRT was found to be most effective when introduced early in menopause, says Anne Marie Minihane, director of the UK’s Norwich Institute of Healthy Ageing at the University of East Anglia. Photo: University of East Anglia

Dr Andrea Kwakowsky from at the University of Galway in Ireland believes the “critical period” for starting HRT is within five years of menopause. Photo: University of Galway

How can you prevent dementia? Free brain health online tool teaches the risks and gives essential tips on avoiding it

The new free “Think Brain Health Check-in” online tool from Alzheimer’s Research UK doesn’t test your memory but checks how well you’re looking after your brain and gives tips to help prevent dementia. Photo: Shutterstock

Dr Susan Mitchell is head of policy at Alzheimer’s Research UK. Photo: Dr Susan Mitchell

The Think Brain Health Check-in asks how often you challenge your brain - and then highlights why challenging your brain is key to staving off dementia. Photo: Shutterstock

Getting a good night’s sleep every night is one way to lower the risk of developing dementia. Photo: Shutterstock

Up to 40 per cent of dementia cases could be prevented if people were mindful of the risk factors for the illness and made lifestyle changes to prevent them. Photo: Shutterstock

Can lack of sleep raise dementia risk? Yes, studies say – but with one exception

Having only five hours of sleep a night can increase dementia risk by 30 per cent for adults over 50, one study says. Photo: Shutterstock

One tip to overcome insomnia is to avoid clock-watching. Photo: Shutterstock

Taking a warm shower or bath in the hour or so before bed may help you fall asleep – and stay asleep. Photo: Shutterstock

Professor Roger Wong of the department of public health and preventive medicine at the State University of New York’s Upstate Medical University. Photo: Roger Wong

Sleep aids can heighten dementia risk, Wong says. Photo: Shutterstock

Can’t sleep? Try getting up and engaging in cognitively stimulating activities, like reading or making jam. Photo: Shutterstock

Dementia and ACB scores: how common prescription and over-the-counter drugs raise the risk of memory loss and cognitive decline

Certain common drugs, including antihistamines, antacids, antidepressants and anti-anxiety medicines, can disrupt the neurotransmitter acetylcholine, dubbed the “memory molecule” increasing the risk of dementia. Photo: Shutterstock

The writer, Anthea Rowan, with her mother. Photo: Anthea Rowan

Taking medications that block the action of acetylcholine can lead to memory loss, problems with spatial awareness, and cognitive decline. Photo: Shutterstock

Studies have found that anticholinergic drugs carried “significant’ dementia risk” for the over-65s. Photo: Shutterstock

Doctors need to be mindful of the risks posed by anticholinergic drugs, especially to an already at-risk population: the over 65s. Photo: Shutterstock

How to safeguard your ageing brain: build ‘cognitive reserve’ with mental and physical exercise, and stay active and socially engaged

The phrase ‘use it or lose it’ is not just a hypothesis, it’s a basic biological fact that holds as true for our brains as our muscles or bones. Photo:
Shutterstock

Our brains, like our muscles need regular use to stay healthy and flexible, say experts, and keeping our brains active builds our ‘cognitive reserve’, helping us to stave off dementia. Photo: Shutterstock

Geriatric psychiatrist Dr David Merrill recommends the active pursuit of activities that keep the brain sharp to stave off dementia. Photo: Dr David Merrill

Dorina Cadar says cultural and social engagement, reading, doing crossword puzzles, visiting art galleries, clubs and cinemas, and volunteering all increase our cognitive reserve. Photo: Dorina Cadar

Visiting an art gallery or doing something new and different are good ways to build up cognitive reserve. Photo: Shutterstock 

How yoga benefits dementia patients: new study uncovers brain-health boosts, supporting earlier research

Yoga has health benefits including better brain neuroplasticity, improved sleep quality, and more robust cardiorespiratory fitness, all of which help people experiencing cognitive decline or dementia. Photo: Shutterstock

Dr Diana Karamacoska is a research support programme fellow in healthy ageing and dementia at the NICM Health Research Institute at Western Sydney University. Photo: Courtesy of Diana Karamacoska

Yoga could be helpful in managing brain inflammation, particularly with its mindfulness component. Photo: Shutterstock

Wendy Du is the founder of Shan Studios in Hong Kong. Photo: Wendy Du/Shan Studios

Du has maintained a daily yoga practice for 10 years. Photo: Courtesy of Shan Studios

5 nutrients good for brain health that can delay dementia, or prevent it, and foods to eat with a high concentration of them

How air pollution increases dementia risk and ways to limit your exposure

People living in polluted areas are more likely to develop Alzheimer’s disease and other dementia types, studies show