A new study published today in the journal Lancet Public Health claims that the number of adults (aged 40 and older) living with dementia is anticipated to nearly triple from 57 million in 2019 to 153 million in 2050.

According to the Global Burden of Disease study, it is the first to provide forecasting projections for 204 countries throughout the world.

The study also examines four risk factors for dementia—smoking, obesity, high blood sugar, and a poor education well as the impact these factors will have on the future trends in the disease.

For example, advances in global education availability are anticipated to reduce dementia prevalence by 61.2 million cases by 2050, a reduction of 61.2 million cases from the current level. Although forecasted rises in obesity, high blood sugar, and smoking may result in an additional 6-8 million dementia cases, this will be offset by the anticipated trends in diabetes and obesity.

The authors emphasize the urgent need to implement locally tailored interventions that reduce risk factor exposure, as well as research to discover effective disease-modifying treatments and new modifiable risk factors, in order to reduce the future burden of disease in the United States and worldwide.

“Our study offers improved forecasts for dementia on a global scale as well as the country-level, giving policy makers and public health experts new insights to understand the drivers of these increases, based on the best available data,” says Emma Nichols, lead author.

“These estimates can be used by national governments to make sure resources and support are available for individuals, caregivers, and health systems globally.”

She continues, “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.”

As of 2019, global dementia care costs are estimated to be more than $1 trillion. Dementia is the seventh most common cause of death in the world. It is also the leading cause of disability and dependency in older people around the world.

Despite the fact that dementia primarily affects the elderly, it is not inevitable in the aging process. An article published in the Lancet Commission on Dementia in 2020 suggested that if 12 known risk factors were eliminated, up to 40 percent of dementia cases could be prevented or delayed. These risk factors included low educational attainment, high blood pressure, hearing impairment (from smoking), midlife obesity (from physical inactivity), diabetes (from diabetes), social isolation (from other people), excessive alcohol consumption (from drinking), head injury (from falling), and air pollution.

The greatest increase in dementia prevalence, according to the study, will occur in eastern Sub-Saharan Africa, where the number of people living with dementia is expected to rise by 357 percent, from nearly 660,000 in 2019 to more than 3 million in 2050, owing to population growth—with Djibouti (473 percent), Ethiopia (443 percent), and south Sudan (396 percent) seeing the largest increases. Similarly, cases in North Africa and the Middle East are expected to climb by 367 percent, from nearly 3 million to nearly 14 million, with particularly substantial increases in Qatar (1926 percent), the United Arab Emirates (1795 percent), and Bahrain (1084 percent ).

The smallest growth in dementia cases is forecast in high-income Asia Pacific, where the number of cases is expected to rise by 53 percent from 48 percent in 2019 to 74 percent in 2050, with a particularly small increase in Japan (27 percent ). The risk of dementia for each age group is predicted to decrease in this region, implying that preventive measures such as improved education and healthy lifestyles are having an effect.

Dementia cases are also anticipated to increase by 74 percent in Western Europe, from nearly 8 million in 2019 to almost 14 million in 2050.  Greece (45 percent), Italy (56 percent), Finland (58 percent), Sweden (62 percent), and Germany (45 percent) are all projected to see slight rises in instances (65 percent ). Dementia cases are expected to rise by 75 percent in the United Kingdom, from just over 907,000 in 2019 to almost 16 million in 2050.

Women are affected by dementia at a higher rate than men around the world. Women with dementia outnumbered males with dementia by a ratio of 100 to 69 in 2019. And it is projected that this tendency will continue till the year 2050.

“It’s not just because women tend to live longer,” adds co-author Dr Jaimie Steinmetz. “There is evidence of sex differences in the biological mechanisms that underlie dementia. It’s been suggested that Alzheimer’s disease may spread differently in the brains of women than in men, and several genetic risk factors seem related to the disease risk by sex.”

According to co-author Professor Theo Vos from IHME, Co-author Professor Theo Vos from the Institute of Health and Medical Education at the University of Washington in the United States says that “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.”

The authors confirm that their study was constrained by a lack of high-quality data in several parts of the world, including Sub-Saharan Africa, Eastern Europe, and Central America, as well as studies that used different dementia methodology and definitions. Moreover, they point out that they were unable to take into account all 12 risk variables identified in the 2020 Lancet Commission report since they were restricted to risk factors identified in the GBD study and only included risk factors with strong evidence of linkage.

Including additional risk variables, on the other hand, would not have resulted in a change in the predicted prevalence unless changes in exposure to a specific risk factor were also foreseen.

Finally, they point out that the study looked at the total prevalence of dementia; clinical subcategories, such as vascular dementia, may have different risk factor associations, which could influence the findings.

Source: 10.1016/S2468-2667(21)00249-8

Image Credit: Getty

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