The Global Burden of Disease study has forecasted the number of dementia diagnosis cases in 195 countries and territories and examined the impact of exposure to important risk factors.
By 2050, 153 million people are expected to have a dementia diagnosis worldwide, up from 57 million in 2019 due to population growth and ageing. Dementia cases will rise in every county, with the smallest estimated increases in high income Asia Pacific (53%) and western Europe (74%), and the largest growth in north Africa and the Middle East (367%) and eastern sub-Saharan Africa (357%).
Experts project that improved access to education could lead to 6 million fewer cases of dementia worldwide by 2050. However, they caution that this decrease would be offset by a projected 7 million additional dementia cases linked to projected rates of obesity, high blood sugar, and smoking.
The Global Burden of Disease study is the first to provide forecasting estimates for 195 countries worldwide.
Living with a dementia diagnosis
The number of adults aged 40 years and older living with a dementia diagnosis worldwide is expected to nearly triple, from an estimated 57 million cases in 2019 to 153 million cases in 2050.
The study focused on four risk factors that can lead to a dementia diagnosis – smoking, obesity, high blood sugar and low education and the impact on future trends. For example, improvements in global education access are projected to reduce dementia prevalence by 6.2 million cases worldwide by 2050. But this will be countered by anticipated trends in obesity, high blood sugar, and smoking, which are expected to result in an additional 6.8 million dementia cases.
The authors highlighted an urgent need to roll out locally tailored interventions that reduce risk factor exposure, alongside increased research into effective disease-modifying treatments and new modifiable risk factors to reduce the future burden of the disease.
“Our study offers improved forecasts for dementia on a global scale as well as the country-level, giving policymakers and public health experts new insights to understand the drivers of these increases, based on the best available data”, said lead author Emma Nichols from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, USA. “These estimates can be used by national governments to make sure resources and support are available for individuals, caregivers, and health systems globally.”
She continued, “At the same time, we need to focus more on prevention and control of risk factors before they result in dementia. Even modest advances in preventing dementia or delaying its progression would pay remarkable dividends. To have the greatest impact, we need to reduce exposure to the leading risk factors in each country. For most, this means scaling up locally appropriate, low-cost programmes that support healthier diets, more exercise, quitting smoking, and better access to education. And it also means continuing to invest in research to identify effective treatments to stop, slow, or prevent dementia.”
Dementia: the seventh leading cause of death globally
Dementia is currently the seventh leading cause of death worldwide and one of the major causes of disability and dependency amongst older people globally—with global costs in 2019 estimated at more than US$1 trillion. However, 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.
Those risk factors included:
- low education,
- high blood pressure,
- hearing impairment,
- smoking,
- midlife obesity,
- depression,
- physical inactivity,
- diabetes,
- social isolation,
- excessive alcohol consumption,
- head injury,
- air pollution.
The study predicted that the greatest increases in dementia diagnosis cases would occur in eastern sub-Saharan Africa. It is expected to grow by 357%, from almost 660,000 in 2019 to more than 3 million cases in 2050.
Further findings indicated that the Asia Pacific will have the smallest increase of 53%, from 4·8 million in 2019 to 7.4 million in 2050. This figure could be attributed to a healthier lifestyle. Similarly, in western Europe, the number of dementia cases is expected to rise by 74%, from almost 8 million in 2019 to nearly 14 million in 2050. Relatively small increases in cases are expected in Greece (45%), Italy (56%), Finland (58%), Sweden (62%), and Germany (65%). The UK will see the number of dementia cases increasing by 75%, from just over 907,000 in 2019 to almost 1.6 million in 2050.
According to co-author Professor Theo Vos from 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 prioritising education and healthy lifestyles. Ensuring that structural inequalities in access to health and social care services can be addressed and that services can additionally be adapted to the unprecedented needs of an increasing older population with complex care needs will require considerable planning at both local and national levels.”
However, the authors acknowledged 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 noted that they could not consider all 12 risk factors from the 2020 Lancet Commission report because they were limited to risk factors included in the GBD study and only included the risk factors with strong evidence of association.
Additionally, the authors noted that although including additional risk factors, it would not have necessarily led to a change in the forecasted prevalence unless there were changes in exposure to a given risk factor. Finally, they stated that the study examined the overall prevalence of dementia; it is possible that clinical subtypes, such as vascular dementia, may have different relationships with risk factors, which could affect the results.
