Japan's health ministry estimates the number of elderly people with dementia will exceed 5.84 million in 2040, when children of postwar baby boomers will turn 65 or older. The figure accounts for about 15 percent of the total elderly population.
A health ministry research team selected four municipalities from across the country. Doctors conducted diagnoses for dementia on people aged 65 or older in the municipalities. The team calculated the prevalence of dementia among the elderly in each municipality and estimated the future nationwide figure.
The previous survey conducted nine years ago estimated 8.02 million people will suffer from dementia in 2040.
The team says the latest estimate is lower because the decline in cognitive function may have been suppressed by improvement in prevention measures for lifestyle-related diseases and a change in health consciousness.
The latest survey estimates for the first time that people who have mild cognitive impairment but are not diagnosed with dementia will be 6.128 million in 2040. Such people have memory loss but have no problem with daily life.
The team says people with mild cognitive impairment often develop dementia. But it says they may be able to slow down the progress of their symptoms by exercising and taking nutritious food.
Experts say the number of people with dementia living alone is expected to increase in the future due to change in family member composition and other factors. They say that local communities should urgently come up with support measures for them as their family support is limited.