A record number of Japanese people with dementia went missing last year, according to figures released on Thursday, underlining the country’s battle to care for the rapidly increasing number of people who have the condition.

The national police agency said 12,208 people with dementia were reported missing in 2015 – an increase of 1,452 from the previous year. Most had wandered off and were found within a day to a week, but 479 were found dead and 150 have yet to be located, according to Kyodo News.

With the over-64s already comprising just over a quarter of its 128 million population, Japan is at the forefront of devising ways to tackle the challenges posed by a super-ageing society, including the stigma attached to people with Alzheimer’s disease and other forms of dementia.

The disorder affects 4.6 million people in Japan, with the number forecast to rise to 7 million – or one in five people aged 65 or over – by 2025.

Under its “orange plan” announced last year, the government is to spend 22.5bn yen (£152.3m) this year to train more specialists, improve early diagnosis and expand community-based care to relieve the pressure on family members who have to give up work to become carers.

In a recent survey 40% of families looking after relatives said they could not continue to provide home-based care, while 70% said their responsibilities had become a burden.

An estimated 100,000 people leave their jobs every year to look after elderly relatives, including those who suffer from dementia – a figure the prime minister, Shinzo Abe, has vowed to cut to zero by 2025, when Japan’s baby boomers will be aged 75 or older.

The potential dangers of people with dementia straying from home were highlighted earlier this year in a landmark case that campaigners hailed as a breakthrough in the law’s attitude towards sufferers.

In March, the supreme court overturned an earlier ruling that had ordered the family of a 91-year-old man with dementia to pay 3.6m yen in compensation to a railway operator after he wandered from home and was killed by a train, causing widespread disruption to rail services.

The supreme court sided with the man’s family, who had spoken of the difficulty of monitoring him around the clock.

Warnings of a looming dementia crisis in Japan have spawned a range of new goods and services that claim to improve cognitive function, from fitness programmes for the over-60s and specially compiled crossword and puzzle books to supplements that claim to improve memory.

