Today, a quarter of Japan's population of 127 million is 65 or over. Some 4.6 million Japanese suffer from dementia; but it's estimated that in just seven years, the figure will soar to 7.3 million or one in five of those 65 and older.
The shift is forcing health and welfare costs skyward. Spiralling costs, together with a corresponding shortage of professional caregivers, is forcing the country to adapt a communal approach to combat the condition's widespread effects.
In 2015, the Japanese government issued its "Orange Plan," a series of adaptive steps including increased support for family caregivers and more frequent home visits by specialized doctors.
The past two decades have given rise to the 'lonely death' phenomenon, in which childless old people die alone in their homes without anyone knowing.
Thousands of dementia sufferers go missing each year — 15,432 in 2016. Of these, hundreds are later found dead.
The crisis has prompted unique community responses. One city gives its citizens iron-on stickers sporting QR codes (a machine-readable optical barcode) — identification tags to help police return dementia patients who have wandered away from their families. Many members of the dementia-supporter, citizen brigades run cafes designated for sufferers and their families.
The dementia surge presents a particularly acute strain on families. Many with the condition have only one child, who must bear the weight of home care alone.
Childless Japanese face the possibility of an even graver end.
The past two decades have given rise to the "lonely death" phenomenon, in which childless old people die alone in their homes without anyone knowing. Typically, their bodies are discovered after their neighbors notice the smell, but some aren't found until years later, once their bank accounts run dry.
With 4,000 lonely deaths occurring each week, there are now thousands of companies across Japan specializing in lonely death cleanup — scrubbing empty houses of body seepage and other traces of decomposition, while gathering the possessions of the dead together for recycling or sale.
These phenomena stem directly from the country's demographic crisis.
With an average life expectancy of almost 84 years, Japan leads the world in longevity. But at 1.41, the nation's fertility rate is among the world's lowest.
Japanese resorted to abortion widely, snuffing out a brief post-World War II population boom.
Since then, the share of the population 15 and under has slumped from 35 percent to just 13 percent.
By the early 1970s, Japan's fertility rate slipped beneath the replacement level, where it has remained since.
Population peaked in 2010 and is now in decline.
Last year, Japan registered 981,000 births — the lowest number since the government conducted its first census in 1899 and the largest net decrease in almost a decade of continuous population decline. Analysts project that by 2050, the population will fall from 127 million today to 107 million.
By that time, 40 percent of the country's remaining population will be over age 65, suggesting dementia patrols and lonely deaths will remain fixtures of Japanese society for generations to come.