TOKYO -- Restaurants in Japan are increasingly jettisoning 24-hour operations in light of slower foot traffic late at night and difficulty finding staff to work such hours.

Japan's largest casual eatery operator, Skylark, now keeps 428 of its 3,000 or so restaurants in Japan open 24 hours. The company will shorten the hours of about 310 of these locations by April, closing them at 2 a.m. It will also close at 2 a.m. about 440 of 559 eateries that currently stay open until 5 a.m.

The changes are seen pushing down Skylark's sales by more than 1 billion yen ($8.46 million).

Although some locations on busy streets will retain round-the-clock operations, the company will re-examine the hours of locations attracting less demand.

One driving factor is lifestyle changes, which have led to a drop-off in younger customers late at night. Another is an effort to improve the work-life balance of an increasingly diverse workforce that includes more women.

A labor shortage is also at work. The most recent Bank of Japan Tankan survey of business sentiment shows a drop in the employment condition index of large lodging and food service companies to minus 38, matching the year-to-date low reached in March.

Due to difficulty attracting part-time and other temporary workers for late-night shifts, full-time employees often work these hours.

Another restaurant company, Royal Holdings, has decided to end 24-hour operations around January at the two Royal Host eateries now open around the clock.

Only 621 locations in the Yoshinoya Holdings beef-bowl chain are open all night -- about half of all locations -- as of the end of October.

McDonald's Holdings (Japan), which operated 57% of its outlets around the clock in late 2012, had scaled that down to around 28%, or 809 locations, by the end of September.

"With the younger population shrinking in Japan, the number of consumers and workers is dropping in late-night hours," said Koya Miyamae of SMBC Nikko Securities. "Due to such efforts as work reform and pay hikes for non-full-time workers, elimination of late-night operations could spread to the entire nonmanufacturing sector."