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Decomposition of the percentage change in the number of people with dementia between 2019 and 2050 globally and by world region. GBD = Global Burden of Diseases, Injuries and Risk Factors Study.
The number of adults (age 40 and older) living with dementia worldwide is expected to nearly triple, from an estimated 57 million in 2019 to 153 million in 2050, primarily due to population growth and aging. of the population. The Global Burden of Disease study is the first to provide prognosis estimates for 204 countries worldwide and is published in The Lancet Public Health .
The study also looks at four risk factors for dementia – smoking, obesity, high blood sugar and low educational attainment – and highlights the impact they will have on future trends. For example, improvements in global education access are projected to reduce the prevalence of dementia by 6.2 million cases worldwide by 2050. But this will be offset by anticipated trends in obesity, high blood sugar, in blood and smoking, which are expected to result in an additional 6·8 million cases of dementia.
The authors highlight the urgent need to implement locally tailored interventions that reduce exposure to risk factors, along with research to discover effective disease-modifying treatments and new modifiable risk factors to reduce the future burden of disease.
"Our study offers improved forecasts for dementia on a global scale, as well as at the country level, providing policymakers and public health experts with new insights to understand the drivers of these increases, based on the best available data," says lead author Emma Nichols from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, US. “National governments can use these estimates to ensure that resources and support are available to people.” , caregivers and health systems worldwide.”
She continues: “At the same time, we need to focus more on preventing and controlling risk factors before they lead to dementia. Even modest advances in preventing dementia or slowing its progression would pay notable dividends. To have the greatest impact, we need to reduce exposure to the main risk factors in each country. For most, this means expanding locally appropriate, low-cost programs that support healthier diets, more exercise, smoking cessation, and better access to education. And it also means continuing to invest in research to identify effective treatments to stop, delay or prevent dementia."
Dementia is currently the seventh leading cause of death worldwide and a leading cause of disability and dependency among older people globally, with global costs in 2019 estimated at more than US$1 trillion [2]. Although dementia primarily affects older people, it is not an inevitable consequence of aging. A Lancet Commission published in 2020 suggested that up to 40% of dementia cases could be prevented or delayed if exposure to 12 known risk factors were eliminated: low education, high blood pressure, hearing impairment, smoking, midlife obesity , depression, physical inactivity, diabetes, social isolation, excessive alcohol consumption, head trauma and air pollution.
The study predicts that the largest increase in prevalence will occur in eastern sub-Saharan Africa, where the number of people living with dementia is expected to increase by 357%, from almost 660,000 in 2019 to more than 3 million in 2050. mainly driven by population growth: Djibouti (473%), Ethiopia (443%) and South Sudan (396%) recorded the largest increases. Similarly, in North Africa and the Middle East, cases are projected to grow by 367%, from nearly 3 million to nearly 14 million, with particularly large increases in Qatar (1,926%), the United Arab Emirates ( 1795%) and Bahrain.
By contrast, the smallest increase in the number of dementia cases is projected in high-income Asia Pacific, where the number of cases is expected to grow by 53%, from 4·8 million in 2019 to 7·4 million in 2050 — with a particularly small increase in Japan (27%). In this region, the risk of dementia for each age group is expected to decrease, suggesting that preventive measures, including improvements in education and healthy lifestyles, are having an impact.
Similarly, in Western Europe, the number of dementia cases is expected to increase by 74%, from almost 8 million in 2019 to almost 14 million in 2050 (table 1). Relatively small increases in cases are expected in Greece (45%), Italy (56%), Finland (58%), Sweden (62%) and Germany (65%). In the UK, the number of dementia cases is expected to increase by 75%, from just over 907,000 in 2019 to almost 1·6 million in 2050.
Globally, dementia affects women more than men. men. In 2019, women with dementia outnumbered men with dementia by 100 to 69. And this pattern is expected to continue in 2050. “It’s not just because women tend to live longer,” says co-author Dr. Jaimie Steinmetz of IHME, University of Washington, USA. “There is evidence of sex differences in the biological mechanisms underlying dementia. "It has been suggested that Alzheimer’s disease may spread differently in the brains of women than in men, and several genetic risk factors appear to be related to disease risk by sex."
According to the co-author, the Professor Theo Vos of IHME, University of Washington, USA, “Low- and middle-income countries in particular should implement national policies now that can mitigate dementia risk factors for the future, such as prioritizing education and lifestyles.” Ensuring that structural inequalities in access to health and social care services can be addressed and that services can be further tailored to the unprecedented needs of a growing older population with complex care needs will require considerable planning at both the local and national levels."
The authors acknowledge that their analysis was limited by a lack of high-quality data in several parts of the world, including sub-Saharan Africa, Eastern Europe, and Central America, and by studies using different methodologies and definitions of dementia. They also note that they were unable to consider the 12 risk factors in the 2020 Lancet Commission report because they were limited to the risk factors included in the GBD study and only included risk factors with strong evidence of association. However, the inclusion of additional risk factors would not necessarily have led to a change in predicted prevalence, unless changes in exposure to a given risk factor were also expected. Finally, they note that the study examined the overall prevalence of dementia and possibly clinical subtypes, such as vascular dementia.
In a linked comment, Dr. Michaël Schwarzinger and Dr. Carole Dufouil of Bordeaux University Hospital in France (who were not involved in the study) say: “In our opinion, the authors’ efforts to take advantage of GBD 2019 still They are oversimplifying the underlying mechanisms that cause dementia...[they] provide apocalyptic projections that do not take into account advisable lifestyle changes throughout the lifespan. "There is a considerable and urgent need to strengthen a public health approach to dementia to better inform people and decision-makers about appropriate means to delay or avoid these dire projections."
Added value of this study
This study leveraged country-specific dementia prevalence estimates from the GBD study to project dementia prevalence globally, by world region, and at the country level. Additionally, we incorporated information on projected trends in exposure to known dementia risk factors to understand how trends in risk factors could affect the projected number of people with dementia, and we did a decomposition analysis to understand the drivers of the predicted changes.
Our age-standardized prevalence estimates remained stable between 2019 and 2050 (percentage change of 0 1% [95% uncertainty interval: −7 5 to 10 8]), while the number of people Estimates of having dementia increased considerably, from 57·4 (50·4–65·1) million cases in 2019 to 152·8 (130·8–175·9) million cases in 2050.
Implications of all available evidence
Due to increasing population growth and aging of the population, huge increases in the number of people affected by dementia can be expected by 2050. Since there are currently no disease-modifying therapies available, appropriate emphasis should be placed on in efforts to address known modifiable risk factors.
Multimodal interventions have shown some success in slowing the rate of cognitive decline and present a promising approach to dementia risk reduction and prevention. At the same time, it will be necessary to plan for expected increases in the use of health and social care services and expand resources to support carers of people with dementia. Finally, continued resources should be directed toward better understanding and characterization of disease mechanisms, with the goal of developing effective therapeutic agents.
