The number of people living with dementia globally more than doubled between 1990 and 2016 from 20.2 million to 43.8 million, report researchers.

The researchers also found that 22.3 percent of healthy years lost due to dementia in 2016 were due to modifiable risk factors. Their study looks at the global, regional, and national burden of Alzheimer’s disease and other dementias from 1990-2016.

The systematic analysis of the Global Burden of Disease Study 2016 found dementia was more common at older ages, with the prevalence doubling every five years over age 50. There was also significant potential for prevention.

“In our study, 22.3 percent (11.8-35.1 percent) of the total global disability-adjusted life years lost due to dementia in 2016 could be attributed to the four modifiable risk factors—being overweight, high blood sugar, consuming a lot of sugar-sweetened beverages, and smoking,” the authors say.

Lead author Cassandra Szoeke, a professor at the University of Melbourne and director of the Women’s Healthy Ageing Project, says even more risk factors would be explored in the new data collection.

By 2050, the number of people living with dementia could be around 100 million

“But already the importance of these risks in allowing us to prevent or delay dementia is clear,” she says. “The paper noted that changes in risk factor exposure over time as we become healthier might account for several cohort studies documenting a reduction in age-specific incidence rates in their study populations.”

Because dementia develops over at least 20 to 30 years before patients get a diagnosis, Szoeke says studies needed to investigate cognition over 20 to 30 years to determine when and for how long intervention is necessary to prevent disease.

She says most randomized controlled trials lasted one to five years and the necessary 30-year longitudinal studies were rare.

“In addition, when you look over decades there are so many exposures that impact on our health, you need to account for all these things or you could miss a factor that is crucial in the development of disease,” she says.

 Global age-standardised prevalence of Alzheimer's disease and other dementias by sex, 2016
Global age-standardised prevalence of Alzheimer's disease and other dementias by sex, 2016
Image: Lancet Neurology

Szoeke says by 2050 the number of people living with dementia could be around 100 million.

“The paper states that to support our community, we will need a larger workforce of trained health professionals as well as planning and building facilities and community-based services which support improved quality of life and function,” she says.

“We need to enhance the quality of life and function of people living with cognitive impairment and focus on preventing further cognitive decline. This will need a codeveloped community wide approach with well-developed services and an even greater network of trained health professionals.

“Chronic diseases are becoming the leading causes of death and disability worldwide, and whilst we continue to work daily on new therapies to target disease, at home we really need to focus more on the health choices that we know extend both disease-free and disability-free survival.”

The research appears in the Lancet Neurology. Researchers from the University of Washington also led the research.