An estimated 20 percent of the more than 42,500 U.S. vehicle crashes a year are linked to drowsy driving, federal health officials said. A report published in the Centers for Disease Control and Prevention Morbidity and Mortality Weekly Report said insufficient sleep can have serious and sometimes fatal consequences for fatigued workers and those around them. The National Sleep Foundation recommends healthy U.S. adults sleep 7-9 hours per day, but 30 percent of civilian employed U.S. adults -- approximately 40.6 million workers -- reported an average sleep duration of fewer than 6 hours per day, the report said. \"The prevalence of short sleep duration fewer than 6 hours per day varied by industry of employment with a significantly higher rate of short sleep duration among workers in manufacturing -- 34.1 percent -- compared with all workers combined,\" the report said. \"Among all workers, those who usually worked the night shift had a much higher prevalence of short sleep duration -- 44 percent representing approximately 2.2 million night-shift workers -- than those who worked the day shift at 28.8 percent, representing approximately 28.3 million day-shift workers.\" There was high prevalence of short sleep duration by night shift workers in the transportation and warehousing at 69.7 percent and 52 percent of the healthcare and social assistance industries, the report said.