Japanese 89-year-old Tomiji Suzuki started coding in retirement and is now making apps for the fast-growing elderly demographic, using ChatGPT to fine-tune his skills.

So far Suzuki has developed 11 free iPhone apps to help Japan's ageing population, including his latest: a slideshow of items to remember when leaving the house, from a wallet and hearing aids to patient registration cards.

He was inspired to create the app, which features his granddaughter's voice, after he realised he had forgotten his dentures as he was about to board a bullet train.

"These kinds of things happen to the elderly," he laughed, telling AFP that his age has been an advantage when coming up with ideas for the programmes.

"No matter how hard they try, I don't think younger people understand the elderly's needs and expectations," he said.

Nearly a third of Japan's population is aged 65 and above, making it the world's oldest country after tiny Monaco, and one in 10 people are octogenarians.

As in other developed economies, the plummeting birth rate has raised fears of a looming demographic crisis with not enough workers to support the growing ranks of retired.