In one senior day care center in Yokohama -- appropriately named after the aforementioned U.S. gambling mecca -- elderly people play mahjong and baccarat as the chimes and pings of slot machines and pachinko fill the room.
"We believe this casino stimulates the brain and helps to prevent or suppress the development of dementia," said Kaoru Mori, Chairman of Japan Elderly Care Service, which runs the "Las Vegas" center.
It's no secret that old people love to gamble. Grey hairs are a common sight everywhere from the casino floors of Vegas to the mahjong parlors of Hong Kong.
Some researchers have argued that gambling could be good for staving off brain disorders common in old age. A study
by the Suwa Tokyo University of Science found that elderly subjects demonstrated an uptick in frontal and parietal lobe activity, and improvements in recognition.
However, others warn that elderly gamers are especially at risk of addiction.
According to U.S. gaming industry data
, half of all adult visitors to casinos in 2013 were aged 50 or older. The AARP, a lobby group that represents retirees, warned that seniors are the fastest growing segment
of gambling addicts in the U.S.
Around 5% of Japanese, or 5.36 million people, are addicted to gambling, according to a 2014 government study
Residents of the Yokohama center say that gaming helps keep their brains sharp, and offers companionship they otherwise miss.
"I've lived alone for decades, many days I don't speak a word, I feel very depressed, but here we play games and talk," one customer told CNN.
Another said: "I use my brain playing mahjong and I use my fingers, I believe it helps stimulate my mind."
Strict rules against betting outside of strictly defined venues in Japan mean that no real money exchanges hands in the Yokohama center -- instead seniors use fake bills and compete for prizes.
This hasn't stopped some municipalities from banning the practice however.
In September, the Kobe Municipal Assembly passed an ordinance banning daycare centers from providing games that "stir up a passion for gambling" or use "pseudo currency" like casino chips.
Experts warn that when real money is involved, older gamblers can be especially vulnerable.
A 2005 study by the University of Pennsylvania found that 70% of seniors surveyed
had gambled in the last year and one in 10 over-65s were at risk of financial problems because of gambling.
Maureen O'Connor, a former mayor of San Diego, gambled more than a billion dollars over 10 years due to what she said was an addiction to gambling aggravated by a brain tumor.
O'Connor only stopped after she was caught embezzling $2 million from a charity set up by her late husband.