Media playback is unsupported on your device Media caption How Japan is keeping people with dementia safe

Each year in Japan thousands of elderly people with dementia go missing, hundreds are never found alive again.

Japan has the world's oldest population but also some of the most advanced technology and they're using it to help keep people with dementia safe.

People like Mrs Itou who lives in the city of Matsudo.

The first time she went missing her son who cares for her went driving around looking for her in the places she normally goes.

That was no easy task as Mrs Itou loves to walk and can cover a hundred kilometres a month.

That time his mother came home, but since then she's gone missing four more times as her dementia has worsened.

'Constant vigil'

The stress of caring for someone with dementia is well known to Nobel prize-winning scientist Randy Schekman whose wife had Parkinson's disease and dementia before she died.

"You have to keep a constant vigil," he tells me at a meeting in Japan of Nobel laureates and other eminent people to discuss the future of ageing.

Media playback is unsupported on your device Media caption The Nobel prize-winner tackling Parkinson's Disease

"As my wife's dementia progressed I couldn't let her go to the restroom when we went out together. She would go in go into a stall, lock the door and then not be able to unlock the door - she was trapped inside a women's restroom."

Prof Schekman describes the projections of the rising number of people with dementia as a crisis akin to climate change because of the stress it will place on those caring for them and the economic consequences as people leave work to care for loved ones.

He is at the start of a 10-year project to tackle the basic science behind Parkinson's disease which will gather teams of scientists from around the world. The project's budget is being provided by Google co-founder Sergey Brin.

Dementia tech

Meanwhile in Japan, people like Mrs Itou are using new practical solutions to deal with memory loss and the need for a constant vigil.

Image caption The QR codes pattern are attached to badges and can be read by a smartphone

The local government provides people with dementia and their carers, with badges they can wear. They display a QR code - a square image similar to a barcode - which can be read by anyone with a smart-phone.

The badges have helped Mrs Itou get home the last two times she went missing.

One of the inventors of the badges, Haruo Hidaka had the idea after watching the grandmother who raised him suffer with dementia.

He believed in the idea so much that his team developed a prototype that he personally went to sell in 630 towns and cities across Japan.

The idea was a success and the company he worked for has been bought by the Japanese pharmaceutical company Toho Holdings.

Image caption Haruo Hidaka is one of the inventors of the QR codes which are being used to help keep people with dementia from getting lost

Talking to me at the company's Tokyo headquarters, Mr Hidaka says as well as his grandmother the idea was also sparked by the case of someone who died in their home and whose death went unnoticed for weeks.

Tackling lonely deaths

This is a common problem in Japan and it's another problem that the city of Matsudo and many others are tackling.

It's a rainy Friday afternoon and a group of 10 Matsudo residents are putting on orange vests and preparing to head out around the city.

The volunteers are just some of thousands across Japan who have been through a programme of dementia awareness.

Image caption Neighbourhood dementia awareness teams in Matsudo go door-to-door in the city checking that people are safe

Today they're going door to door with flyers for a pop-up cafe. While posting the adverts they're also keeping an eye out for houses where there are telltale signs of problems, like mail piling up. That could be the sign of someone inside in trouble or perhaps even dead.

"One shouldn't be pointing fingers, but I think you can tell straight away," says Manami Yoshii.

"By putting flyers into the postbox, we are able to check whether their postboxes are overflowing. And through that we would be able to tell if something might have happened to the resident."

The pop-up cafes they are advertising are a place where older people can come and get lunch and a chat.

Cafe connections

While developments like QR codes are useful, they're not the full solution, according to Akiko Saito who runs one of Matsudo's dementia cafes.

"These days our relationships with our immediate neighbours are fading," she says as about 20 local pensioners dig in to a typical multi-dish Japanese lunch.

Image caption Akiko Saito runs one of Matsudo's dementia cafes, she believes that we can't just on technological solutions for helping an older population

"We are connected through things like social networking sites, but in case there is a disaster or if something happens, I think it's going to be more and more important in future to have a space where you can build relationships between people so that neighbours would be able to help each other out."

With our life expectancy rising in most countries, the number of people with dementia is expected to increase dramatically in the coming decades.

The solutions they have found in super-ageing Japan are already being copied in other countries and are likely to spread even further.

Additional reporting by Tamasin Ford and Erica Symonds

This content was created as a co-production between Nobel Media AB and the BBC