They would enter the bank and ask for their cash. Yuriko Asahara, behind the counter, would check where they would stash it — in the side pocket of a handbag or perhaps deep down in a shoulder bag.

Asahara wasn't spying. She knew she'd have to remind them within an hour or two. Many of her clients suffered from dementia, and over the course of two decades the bank manager became a self-taught expert on the disease.

Globally, an estimated 44.4 million people suffer from dementia and the figure is projected to triple to 135.5 million in 2050 as the population ages, Alzheimer's Disease International estimates. Nowhere is the problem more acute than in Japan, where an estimated 8 million people have dementia or show signs of developing it. By 2060, 40 percent of Japanese will be over 65, up from 24 percent today, according to the National Institute of Population and Social Security Research.