One in five elderly people in Japan will have dementia in 2025, according to the government's new estimate released Wednesday.

The number of dementia patients in Japan will reach between 6.75 million and 7.3 million in 2025 when postwar baby boomers turn 75 or older, the health ministry said in a projection.

A research team at the Ministry of Health, Labor and Welfare put the estimated number of dementia patients at 65 or older in 2012 at around 4.62 million.

The new projection was included in the ministry's draft national strategy for enhancing dementia measures that was disclosed at a meeting of the Liberal Democratic Party. The government will shortly finalize the strategy, made up of seven major policies including measures focusing on the needs of the patients and their families.

At an international conference on dementia in Tokyo last November, Prime Minister Shinzo Abe vowed to devise a national strategy for tackling the age-linked illness in the rapidly graying country.

From fiscal 2016, the government plans to launch a long-term study of 10,000 patients across the country to investigate the mechanism through which the illness develops.

The degenerative disease often starts as memory lapses, then progresses to more severe impediments such as losing track of time and place, and loss of mobility.

According to the 2013 health ministry study, Alzheimer's is the most prevalent type of dementia, affecting two thirds of the patients. Nearly 20 percent have vascular dementia, caused by strokes. The third most common type is Lewy body dementia, which plagues 4.3 percent of all patients, and is closely associated with Parkinson's disease.

The study also found women were more susceptible, particularly those aged 85 and above.