Tokyo (AFP) - A Japanese city has introduced a novel way to keep track of senior citizens with dementia who are prone to getting lost -- tagging their fingers and toes with scan-able barcodes.

A company in Iruma, north of Tokyo, developed tiny nail stickers, each of which carries a unique identity number to help concerned families find missing loved ones, according to the city's social welfare office.

The adhesive QR-coded seals for nails -- part of a free service launched this month and a first in Japan -- measure just one centimetre (0.4 inches) in size.

"Being able to attach the seals on nails is a great advantage," a city worker told AFP.

"There are already ID stickers for clothes or shoes but dementia patients are not always wearing those items."

If an elderly person becomes disorientated, police will find the local city hall, its telephone number and the wearer's ID all embedded in the QR code.

The chips remain attached for an average of two weeks -- even if they get wet -- the official said, citing recent trials.

Japan is grappling with a rapidly ageing population with senior citizens expected to make up a whopping 40 percent of the population around 2060.

Last month, Japanese police started offering noodle discounts at local restaurants to elderly citizens who agreed to hand in their driving licences.

The offer followed a series of deadly accidents involving elderly drivers -- a growing problem in a country where 4.8 million people aged 75 or older hold a licence.