5.84 Million Elderly in Japan Expected to Have Dementia in 2040; Morbidity Rate For 65 and Older Down From Earlier Prediction

Yomiuri Shimbun file photo
Kyushu University

The number of dementia patients aged 65 and older will soar to an estimated 5.84 million in 2040, around the same time the elderly population will peak in Japan, researchers have said.

This means approximately one in seven members of the elderly population will have dementia, according to a Wednesday announcement by a team of researchers from Kyushu University and elsewhere.

People with mild cognitive impairment (MCI), which is considered a precursor to dementia, are likewise expected to increase to 6.12 million in 2040. This is the first estimate on the number of elderly with MCI.

According to the team’s estimates, there were 4.43 million elderly people with dementia in 2022 and will be 4.71 million in 2025. The 2025 figure is significantly lower than about 7 million that has been projected by the Health, Labor, and Welfare Ministry in other estimates.

Dementia is a condition in which people experience a decline in memory, judgment and other brain functions, which makes it difficult to pursue their daily lives. There are various types of dementia, including Alzheimer’s disease and vascular dementia caused by brain infarction and other factors.

In contrast, MCI does not significantly hinder the lifestyle of the patient. While some MCI patients develop dementia, others return to normal cognitive function.

The research was conducted in four areas including Hisayama, Fukuoka Prefecture, and Ama, Shimane Prefecture, from fiscal 2022 to 2023. Residents aged 65 and older were examined by medical specialists to calculate the dementia morbidity rate in each age group.

Researchers found that the morbidity rate increased with age, and the rate among people aged 65 and older was 12.3% in 2022.

With the aging of the population, the number of elderly people with dementia was estimated to increase to 5.86 million in 2050 and to 6.45 million in 2060.

The MCI morbidity rate among the elderly was calculated to be about 15.5%, equivalent to 5.58 million people, in 2022. The figure was expected to increase to 5.64 million in 2025 and 6.32 million in 2060.

In 2013, another research team cited 15% as the dementia morbidity rate among people aged 65 and older. “It’s possible that cognitive decline has been thwarted by a decrease in the smoking rate and improved management of ailments such as high blood pressure and diabetes,” said Toshiharu Ninomiya, a professor of epidemiology at Kyushu University and leader of the research team.

The government plans to formulate a basic plan by this autumn to promote comprehensive measures related to dementia based on the basic law on the disease, which came into effect in January. Authorities seek to promote efforts to create communities where people with dementia can live independently.