The population's graying is accelerating, with centenarians in Japan expected to reach 40,399 in midmonth, breaking the 40,000 threshold for the first time, a government survey showed Friday.

The annual survey, conducted ahead of Respect-for-the-Aged Day on Sept. 21, also showed that the numbers of both male and female centenarians are increasing to record highs.

The estimated total is up by 4,123 over last year, and is the 39th consecutive year the number has risen. Women make up 86.5 percent of the total, at 34,952, which is 3,739 more than last year, and also the 39th straight year the number has risen. At 5,447, there are 384 more male centenarians than last year, marking the 29th straight year the number has risen, the Ministry of Health, Labor and Welfare said.

The oldest woman, 114, lives in Okinawa. Her name has been withheld at her family's request, while the oldest man is Jiroemon Kimura, 112, who lives in Kyotango, Kyoto Prefecture.

The pace of the increase has accelerated since the survey began in 1963. The number will exceed 40,000 only two years after topping the 30,000 mark in 2007, which was four years after it reached 20,000 in 2003, and five years from seeing 10,000 in 1998.

In a recent interview, Kimura, who was born in April 1897 and lives with two family members, said the secret to his longevity is "to eat a modest amount without likes and dislikes."

He fathered seven children and now has more than 20 great-grandchildren and nine great-great-grandchildren.