TOKYO (AFP) - The number of centenarians in Japan has topped 40,000 for the first time, a government survey showed Friday, amid fears of a looming demographic crisis in the worlds number two economy. There are expected to be 40,399 people aged 100 and older in Japan by mid-September, up 11 percent from a year earlier, the health ministry said. Nearly 35,000, or 87 percent, of the group are women, the survey showed. The oldest person in Japan is a 114-year-old woman living in southern Okinawa, famous for having Japans highest concentration of centenarians. That longevity has been attributed to the islands warm climate and a vegetable-based diet. Okinawa counts roughly 67 centenarians for every 100,000 people, while Japans urban areas have the lowest concentration of 100-year-olds and over. A 112-year-old hailing from the western prefecture of Kyoto is the countrys oldest man. With more than 36 descendants, he has previously said his secrets to longevity are spending hours reading the newspaper and not being a fussy eater. Japan has one of the worlds oldest populations, with many young people putting off starting a family because of the burden on their lifestyles and careers. The government is struggling to find ways to boost Japans birthrate trend to avert a future crisis as a shrinking number of workers is asked to support a growing mass of pensioners. The fertility rate edged up to 1.37 children per woman in 2008, but the population is on an overall downward trend because the number of women has steadily fallen and fewer people are marrying, the government has said.