The number of people developing dementia worldwide each year could more than double from 11.4 million in 2023 to 24.7 million by 2050, according to a major international study.
The research, published Monday in JAMA Neurology, analyzed individual data from 38,418 participants across 22 population-based studies in 18 countries and territories on six continents.
Across more than 287,000 person-years of monitoring, 3,001 participants developed dementia. The researchers calculated a global age- and sex-standardized incidence rate of 9.7 new cases per 1,000 person-years.
Incidence measures how frequently new cases develop, rather than prevalence, which refers to the total number of people already living with a condition.
After researchers accounted for differences in age, the incidence rate among women was 10.6 cases per 1,000 person-years, compared with 8.6 among men.
The difference between countries at different income levels was greater. Low- and middle-income countries recorded 13.6 cases per 1,000 person-years, compared with 8.3 in high-income countries.
"For the first time, we can compare dementia incidence across a geographically diverse group of populations using the same statistical approach, giving us a clearer picture of where and among whom new cases are occurring,” said lead author Ashleigh Vella of the University of New South Wales’ Centre for Healthy Brain Ageing.
"What stands out is that dementia incidence is not evenly distributed. We see higher rates among women and in low- and middle-income countries,” she added.
The projection of 24.7 million annual cases in 2050 was calculated by applying the study’s age- and sex-specific incidence rates to expected population figures. It assumes that incidence rates remain constant, meaning the projected rise is driven largely by population growth and aging.
Researchers said the findings could help governments anticipate future demand for diagnosis, treatment, long-term care and support services, particularly in lower-resource countries that have historically been underrepresented in dementia studies.
Dementia currently affects more than 57 million people worldwide, while previous research has projected that the number living with the condition could approach 150 million by 2050.
Study co-author Henry Brodaty said 24 million new cases each year would place "enormous pressure on individuals, families, health systems and economies around the world.”
"Population aging means we cannot simply wait for people to develop dementia and then respond,” he said, calling for action to reduce modifiable risk factors, identify people at risk earlier and improve diagnosis, treatment and care.