The number of living people with dementia worldwide is set to triple by 2050, research suggests.
Dementia is an umbrella term for a loss of brain function, with Alzheimer's being the most common form of the disease.
In the UK alone, 850,000 people live with dementia, which is expected to increase to 1.6 million by 2040.
On a global scale, scientists from the University of Washington predict cases will rise from the 57 million in 2019 to 152 million by 2050. This is based on an anticipated increase in risk factors like smoking, obesity and diabetes.
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Why dementia occurs is often unclear. Experts generally agree that what is good for the heart is good for the brain. They therefore encourage people to eat a nutritious diet, exercise regularly and quit smoking.
"Improvements in lifestyle in adults in developed countries and other places – including increasing access to education and greater attention to heart health issues – have reduced incidence in recent years, but total numbers with dementia are still going up because of the ageing of the population," said Dr Maria Carrillo, chief scientific officer of the Alzheimer's Association, which partly funded the study.
"In addition, obesity, diabetes and sedentary lifestyles in younger people are rising quickly – and these are risk factors for dementia."
The Washington scientists analysed data from the Global Burden of Disease study, a set of estimates on global health trends based on information collected between 1999 and 2019.
Results – presented at the Alzheimer's Association International Conference – suggest 152 million people will have dementia in 2050, a 166% increase from the estimated 57 million cases in 2019.
Patient numbers are expected to particularly rise in eastern sub-Saharan Africa, North Africa and the Middle East.
This is largely down to population growth and a rising life expectancy. People aged over 65 are set to make up 16% of the world's population by 2050, up from 8% in 2010.
Conversely, the Washington scientists found improvements in education will prevent 6.2 million dementia cases up to 2050.
Nevertheless, a rise in smoking, blood sugar levels and obesity specifically are expected to trigger 6.8 million incidences.
"These estimates will allow policymakers and decision makers to better understand the expected increases in the number of individuals with dementia, as well as the drivers of these increases in a given geographical setting," said study author Emma Nichols.
"The large anticipated increase in the number of individuals with dementia emphasises the vital need for research focused on the discovery of disease-modifying treatments and effective low-cost interventions for the prevention or delay of dementia onset."
Dementia has no single diagnostic test. Medics often carry out mental ability assessments and study brain scans for signs of the disease. There is also no cure for dementia, with treatments only easing its symptoms.
Writing in Alzheimer's & Dementia: The Journal of the Alzheimer's Association, the Washington scientists recently reported Alzheimer's-related deaths rose by more than a third (38%) between 1990 and 2019.
"Without effective treatments to stop, slow or prevent Alzheimer's and all dementia, this number will grow beyond 2050 and continue to impact individuals, caregivers, health systems and governments globally," said Dr Carrillo.
"In addition to therapeutics, it's critical to uncover culturally-tailored interventions that reduce dementia risk through lifestyle factors like education, diet and exercise."
A two-year study aims to uncover whether lifestyle interventions that target many risk factors may protect cognitive function in at-risk older people.
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Also presented at the Alzheimer's conference, a study suggests 10 in every 100,000 people (0.01%) who develop dementia are diagnosed before 65 – equating to 350,000 early-onset cases globally every year.
"People living with younger-onset Alzheimer's face unique challenges when it comes to diagnosis, family, work, finances, future care and possible treatment options, but support and information is available," said Kristen Clifford, chief programme officer at the Alzheimer's Association.
"You have the power to make a new plan and determine how you choose to live your best life with the disease."
Scientists have also revealed the number of people who died from Alzheimer's rose from 16 to 30 per 100,000 fatalities – an 87% increase – in the US alone from 1999 to 2019, with rural regions being the worst affected.
"Our work shows there is an increasing discrepancy in Alzheimer's mortality between urban and rural areas," said Dr Ambar Kulshreshtha, from Emory University in Atlanta.
"This discrepancy could be related to – or might be the result of – other urban-rural health disparities, including access to primary care and other health services, socio-economic level, time to diagnosis and the rising proportion of older Americans living in these areas."
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