It's always nice to get the full recommended seven or nine hours of sleep every day. But life—and work—often gets in the way. And getting too little sleep can decrease attention and short-term memory and can also alter rational judgment—in addition to increasing the risk for some diseases and making it harder to lose weight.

Thus, for those who work in an industry where a simple error can lead to injury or death, missing out on sleep can be seriously dangerous. Moreover, according to a new survey, workers in industries with heavy equipment are among the least likely to be well rested.

A study of more than 15,000 employed U.S. adults shows that 30 percent of all workers reported getting fewer than six hours of sleep every day. That's some 28.3 million workers who are operating (themselves and often machinery) with far less sleep than recommended. The findings were published online April 27 by the U.S. Centers for Disease Control and Prevention (CDC).

Night shift workers were, predictably, the most likely to be getting less z’s, with 44 percent—some 2.2 million people—getting fewer than six hours a day. (Trying to sleep during daylight hours can be a challenge because the body's circadian rhythms are more likely to be sending stay-awake hormonal signals.)

Of people who work in transportation and warehousing on overnight shifts, almost 70 percent are getting fewer than six hours of sleep a day. This is of particular concern considering that at least one in five vehicle accidents is the result of a fatigued driver.

More than half (about 52 percent) of those working overnight in health care and other assistance industries reported fewer than six hours of sleep. Fatigue in the medical field has been shown to increase both errors and injuries. A 2007 study found that medical trainees who were sleep-deprived were three times as likely to accidentally stick themselves with a needle.

Other sectors that were likely to be getting little sleep (for any shift) were mining (at about 42 percent), utilities workers (at 38 percent) and manufacturing (about 34 percent).

"Short sleep duration is associated with various adverse health effects (e.g., cardiovascular disease or obesity), decreased workplace and public safety, and impaired job performance," wrote the report authors, led by Sara Luckhaupt, of the CDC's National Institute for Occupational Safety and Health.

Workplace safety might sound like the lame stuff of training videos and OSHA (Occupational Safety and Health Administration) posters. But in the U.S., thousands of workers still die from on-the-job injuries every year. And some 2.7 million workers had to go to the emergency room after sustaining an injury on the job in 2010 alone. Personal safety aside, these accidents are expensive. Fatal injuries on the job cost the U.S. some $6 billion annually, and nonfatal workplace injuries drain some $186 billion, according to the CDC. The agency points out that April 28 is the other Memorial Day: Workers Memorial Day, to recognize "those workers who have died or sustained work-related injuries or illnesses." Presumably those insults are more substantial than the familiar paper cut.

Aside from individual attention to sleep habits and health, sleeping times can also be boosted by better policies. One way employers could help those with variable shifts, for example, is by "rotating workers forward from evening to night shifts rather than backward from night to evening shifts," which "makes it easier for circadian rhythms to adjust so that workers can sleep during their rest times," Luckhaupt noted.

And not everyone who is burning the midnight oil is missing out on sleep. Those who work nights in the "arts, entertainment and recreation" fields seem to be doing just fine sleeping in. Less than 10 percent of them reported getting fewer than six hours of sleep.