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Avoiding air pollution from fireplaces and vehicle emissions is among a suite of new dementia prevention recommendations from the World Health Organisation (WHO), which have not endorsed supplements or menopausal hormone therapy to cut the risk of cognitive decline.
Up to 45 per cent of dementia risk could be prevented or delayed by eliminating modifiable risk factors including tobacco, alcohol, not exercising, diabetes and high blood pressure, according to the first update to the WHO’s dementia prevention guidelines in seven years.
But the WHO’s expert dementia panel, drawing on the latest evidence of dementia risk and effective treatments, stressed that individuals alone won’t make a dent in the prevalence of dementia without government action.
“We know more today than ever before about what drives dementia risk, and these guidelines translate that knowledge into action,” said WHO director-general Dr Tedros Adhanom Ghebreyesus.
“Countries now have clear, evidence-based recommendations they can put into practice immediately to protect people’s cognitive health.”
A healthy diet rich in leafy greens, berries, nuts and olive oil, and low in processed and ultra-processed foods, along with physical activity and daily cognitive stimulation, were among the most crucial dementia prevention strategies.
The latter could be taking a course, learning a language, attending public lectures, reading and playing games: “things that actually challenge your brain. It’s not just doing the same crossword every day,” said Scientia Professor Kaarin Anstey, director of the UNSW Ageing Futures Institute and the only Australian on the WHO’s dementia panel.
Anstey also stressed that reducing exposure to household and ambient air pollution, such as PM2.5 particulates from vehicle emissions, was important and warranted new conditional recommendations.
“What a lot of people don’t realise is that the risk isn’t just for those living next door to a polluting factory. A lot of us are exposed to air pollution living in cities,” she said. “The smoke produced from burning a fire in your fireplace can have negative health effects.”
Conversely, the guidelines strongly recommended against vitamin and mineral supplements to reduce the risk of cognitive decline and dementia, specifically vitamins B and E, omega-3 polyunsaturated fatty acids and multivitamins and minerals.
A potentially controversial update to the guidelines, Anstey said, was a conditional recommendation against menopausal hormone therapy (MHT) specifically for reducing the risk of cognitive decline or dementia in post menopausal women aged 65 years and older.
There was also insufficient evidence for or against MHT for women experiencing premature ovarian insufficiency, early menopause or perimenopause for the specific purpose of reducing cognitive decline or dementia risk.
The International Menopause Society does not recommend initiation of MHT for primary prevention of [Alzheimer’s Dementia] in naturally menopausal women, but it noted estrogen therapy was associated with a reduced risk of Alzheimer’s disease in women with premature ovarian insufficiency.
“The evidence base for this is very messy,” Anstey said. “We’re basing these guidelines on the evidence through a very rigorous process. We look at the whole of the literature, its methodologies, and synthesise it all.”
The new guidelines also found insufficient evidence to recommend interventions for depression, sleep, stroke, traumatic brain injury, vision impairment and HIV for the specific purpose of reducing dementia risk.
Other key updates backed interventions to combat midlife obesity and overweight, hearing aids for people with hearing loss, and social engagement interventions to guard against loneliness and isolation.
More than 57 million people live with dementia worldwide, and nearly 10 million people get newly diagnosed every year. Alzheimer’s disease is the most common form of dementia and is estimated to account for 60 to 70 per cent of cases.
Dementia, including Alzheimer’s disease, is Australia’s biggest killer, outstripping cardiovascular disease. An estimated 446,500 Australians will have dementia in 2026, according to the Australian Institute of Health and Welfare.
“In order to achieve the reduction [of 45 per cent] we would have to eliminate the risk factors [obesity, insufficient activity], which is not going to happen,” Anstey said.
“I think we can get some significant mitigation, but there needs to be whole-of-population interventions to really pull it down,” she said. “It has to be a whole-of-government response”.
“We have to look at solutions at a societal level. This is not all down to the individual because there are social and commercial determinants of health, like access to and affordability of healthy food and exercise.”
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