Women in their 70s and 80s exposed to high levels of air pollution suffer a greater decline in memory, a study suggests.
Scientists warned they are also at more risk of Alzheimer’s – the most common form of the memory-robbing disease dementia.
Scans of almost 1,000 women from the US showed those regularly exposed to toxic air over the course of three years lost more brain cells.
This process, called brain atrophy, destroys communication in the brain and is seen in patients with Alzheimer’s.
Although there are plenty of studies linking pollution to dementia, this is the first to demonstrate physical changes in the brain with scans.
Women in their 70s and 80s exposed to high levels of air pollution suffer a greater decline in memory and brain cell death, a US study shows
The number of people with dementia is expected to soar worldwide, increasing from 50million in 2018 to 152million in 2050, according to Alzheimer’s Research.
In the UK, some 850,000 people in the UK have dementia, which is likely to reach one million by 2025.
Cases have been growing over the past few decades, and scientists have taken an interest in pollution being a potential cause.
The University of Southern California study, published in Brain, looked at one of the main types of pollution – PM2.5 particles.
PM2.5 come from traffic exhaust, smoke and dust and their tiny size allows them to remain airborne for long periods.
They are about one 30th the width of a human hair, so small they can be inhaled into the lungs, enter the blood stream and travel to the brain.
DEMENTIA DEATH TOLL DOUBLES IN A DECADE
Dementia is contributing to the deaths of twice as many elderly people as it did a decade ago, data revealed in June.
Figures from Public Health England (PHE) showed the memory-robbing disorder was involved in one in four deaths among people aged 75 or over in England in 2017.
This is double the number of fatalities in 2007, when dementia killed just 12.8 per cent of pensioners.
Experts have called the condition, which causes the progressive death of brain tissue and is the UK’s biggest killer, the ‘health crisis of our time’.
PHE’s figures record how many people had dementia as a contributing or underlying cause of death, so they may also have had terminal cancer or heart disease.
The statistics came just days after it was announced the number of people over the age of 65 living with the condition has hit an all-time high.
A total of 453,881 over-65s were living with the brain-destroying illness in May, a rise of more than 17,000 from the same time last year.
Previous research has suggested fine particle pollution exposure increases the risk for Alzheimer’s and dementia as a whole. This is thought to be because tiny pollutants may cause inflammation – a problem which may trigger dementia.
A direct link has still not been found. And what scientists haven’t discovered is whether PM2.5 alters brain structure and accelerates memory decline.
Andrew Petkus, an assistant professor of clinical neurology at USC and a co-author of the study said: ‘This is the first study to really show, in a statistical model, that air pollution was associated with changes in people’s brains and that those changes were then connected with declines in memory performance.
‘This study provides another piece of the Alzheimer’s disease puzzle by identifying some of the brain changes linking air pollution and memory decline.
‘Each research study gets us one step closer to solving the Alzheimer’s disease epidemic.
‘Our hope is that by better understanding the underlying brain changes caused by air pollution, researchers will be able to develop interventions to help people with or at risk for cognitive decline.’
Dr Katy Stubbs, of Alzheimer’s Research UK, said there is a ‘pressing need’ to identify potential risk factors for dementia, considering one in people born today will develop it in their lifetime.
On the back of the findings she said: ‘The link between air pollution and dementia risk is a growing area of research.
‘This study links greater exposure to air pollution… but the study didn’t look at how many people actually went on to develop the disease.’
The research, led by Dr Diana Younan, used data from women aged 73 to 87 who had up to two brain scans five years apart as part of the Women’s Health Initiative, launched in 1993.
Those brain scans were compared with people who had Alzheimer’s, and scored on their similarity by a machine which had been ‘trained’ to learn Alzheimer’s patterns.
The researchers also gathered information about where the women lived to estimate their exposure to fine particle pollution.
The findings show a link between higher pollution exposure and progressive atrophy of grey matter in the brain, which processes information.
In Alzheimer’s, connections break down as neurons are injured and die throughout the brain. Many regions begin to shrink.
By the final stages of Alzheimer’s, this process – called brain atrophy – is widespread, causing significant loss of brain volume.
High pollution was also linked with memory problems, as women in the study also had annual memory test which measured their ability to recall information quickly and learn new things.
Alzheimer’s is thought to be largely caused by genetics, with smoking, obesity and lack of exercise increasing the risk.
But the findings took into account risk factors including lower income, education, race and cigarette smoking.
The findings are concerning considering the World Health Organisation (WHO) estimates 91 per cent of the world’s population lives in places where air quality exceeds WHO guideline limits.
Earlier this year, researchers at the University of New South Wales claimed cases of dementia are being propelled at a rate of more than 20 per cent a year due to toxic air.
Researchers from King’s College and St George’s, University of London last year found that people living in areas polluted by traffic and industry are 40 per cent more likely to develop dementia.
They calculated that air pollution could be responsible for 60,000 cases of dementia in the UK.
Fine particle pollution has already been blamed for cases of asthma, cardiovascular disease, lung disease and premature death.
More than 40,000 people in the UK are thought to die early every year because of air pollution.
There is currently no cure for Alzheimer’s, which is leading cause of death in the UK and sixth-leading cause in the US.
Dr Stubbs said: ‘The best evidence suggests that staying socially, mentally and physically active, eating a healthy balanced diet, not smoking, drinking only within the recommended limits and keeping weight, cholesterol and blood pressure in check are all good ways to support a healthy brain as we age.’
WHAT HAVE RECENT STUDIES SHOWN POLLUTION CAN DO TO OUR HEALTH AND BODIES?
CAUSE CHILDREN TO HAVE A LOW IQ: Researchers at the University of California, San Francisco, found in May 2019 that children born to mothers who live in polluted areas have an IQ that is up to seven points lower than those living in places with cleaner air.
CAUSE CHILDREN TO HAVE POORER MEMORY: Researchers at the Barcelona Institute for Global Health found boys exposed to greater levels of PM2.5 in the womb performed worse on memory tests by the time they are 10.
DELAY THE DEVELOPMENT OF CHILDREN: Youngsters who live less than one-third of a mile away from busy roads are twice as likely to score lower on tests of communication skills in infancy, found researchers at Eunice Kennedy Shriver National Institute of Child Health in April. They were also more likely to have poorer hand-eye coordination.
MAKE CHILDREN MORE ANXIOUS: University of Cincinnati scientists claimed pollution may alter the structure of children’s brains to make them more anxious. Their study of 14 youngsters found rates of anxiety was higher among those exposed to greater levels of pollution.
CUT YOUR CHILD’S LIFE SHORT: Children born today will lose nearly two years of their lives because of air pollution, according to a report by the US-based Health Effects Institute and the University of British Columbia in April 2019. UNICEF called for action on the back of the study.
RAISE A CHILD’S RISK OF AUTISM: Researchers at Monash University in Australia discovered youngsters living in highly polluted parts of Shanghai have a 86 per cent greater chance of developing ASD. Lead author Dr Yuming Guo said: ‘The developing brains of young children are more vulnerable to toxic exposures in the environment.’
CAUSE ASTHMA IN CHILDREN: Four million children around the world develop asthma each year because of road traffic pollution, a major study by academics at George Washington University estimated. Experts are divided as to what causes asthma – but exposure to pollution in childhood increases the risk by damaging the lungs.
MAKE CHILDREN FAT: University of Southern California experts found last November that 10 year olds who lived in polluted areas when they were babies are, on average, 2.2lbs (1kg), heavier than those who grew up around cleaner air. Nitrogen dioxide pollution could disrupt how well children burn fat, the scientists said.
LEAVE WOMEN INFERTILE EARLIER: Scientists at the University of Modena, Italy, claimed in May 2019 that they believe pollution speeds up ageing in women, just like smoking, meaning they run out of eggs faster. This was based on them finding almost two-thirds of women who have a low ‘reserve’ of eggs regularly inhaled toxic air.
RAISE THE RISK OF A MISCARRIAGE: University of Utah scientists found in January that pregnant women are 16 per cent more likely to suffer the heartbreak of a miscarriage if they live in areas of high pollution.
RAISE THE RISK OF BREAST CANCER: Scientists at the University of Stirling found six women working at the same bridge next to a busy road in the US got breast cancer within three years of each other. There was a one in 10,000 chance the cases were a coincidence, the study said. It suggested chemicals in the traffic fumes caused the cancer by shutting down the BRCA genes, which try to stop tumours growing.
DAMAGE A MAN’S SPERM: Brazilian scientists at the University of Sao Paulo found in March that mice exposed to toxic air had lower counts and worse quality sperm compared to those who had inhaled clean air since birth.
MAKE MEN LESS LIKELY TO GET SEXUALLY AROUSED: Scientists at Guangzhou Medical University in China found rats exposed to air pollution struggled to get sexually aroused. Scientists believe it may also affect men, as inhaling poisonous particles may trigger inflammation in blood vessels and starve the genitals of oxygen – affecting men’s ability to become sexually aroused.
MAKE MEN MORE LIKELY TO HAVE ERECTILE DYSFUNCTION: Men who live on main roads are more likely to have difficulty getting an erection due to exposure to pollution, a Guangzhou University in China study suggested in February. Toxic fumes reduced blood flow to the genitals, tests on rats showed, putting them at risk of developing erectile dysfunction.
RAISE THE RISK OF PSYCHOSIS: In March, King’s College London scientists linked toxic air to intense paranoia and hearing voices in young people for the first time. They said uncovering exactly how pollution may lead to psychosis should be an ‘urgent health priority’.
MAKE YOU DEPRESSED: Massachusetts Institute of Technology researchers found in January that that the more polluted the air, the sadder we are. Their study was based on analysing social media users in China alongside the average daily PM2.5 concentration and weather data where they lived.
CAUSE DEMENTIA: Air pollution could be responsible for 60,000 cases of dementia in the UK, researchers from King’s College London and St George’s, University of London, calculated last September. Tiny pollutants breathed deep into the lungs and enter the blood stream, where they may travel into the brain and cause inflammation – a problem which may trigger dementia.