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GROTON, Conn. (AP) — The U.S. Navy has endorsed changes to submarine sailors' schedules based on research into sleep patterns by a military laboratory in Connecticut.

With no sunlight to set day apart from night on a submarine, the Navy for decades has staggered sailors' working hours on schedules with little resemblance to life above the ocean's surface.

But the scientists at the Naval Submarine Medical Research Laboratory concluded submarine sailors, who traditionally begin a new workday every 18 hours, show less fatigue on a 24-hour schedule.

The first submarine to try the new schedule on a full deployment was the USS Scranton, led by Cmdr. Seth Burton. He said he found during the seven-month deployment that the more consistent sleep pattern made up for any effects of working slightly longer shifts.