New research suggests that insomnia is strongly associated with cognitive impairment in night shift workers.

American researchers found that night shift workers, classified as alert insomniacs, had the highest level of impairment in work productivity and cognitive function. This occupational impairment was more severe in alert insomniacs than in insomniacs with excessive sleepiness.

They also found that alert insomniacs reported significantly greater fatigue than sleepy insomniacs, which emphasizes the clinical importance of distinguishing between fatigue and sleepiness.

"Our findings are important to everyone who is dealing with night shift work," Valentina Gumenyuk, principal investigator of the study, said in a statement. "Our study reaffirms that insomnia within shift work disorder demands clinical attention, and it suggests that treatments focusing on the relief of excessive sleepiness in shift work disorder may not sufficiently improve work-related outcomes."

For the study, researchers collected and analyzed data from 34 permanent night workers, 26 of whom were diagnosed with shift work disorder. Shift work disorder is associated with a recurring work schedule, such as night shifts or rotating shifts, that overlaps the usual time for sleep, and is characterized by a reduction in total sleep time along with complaints of insomnia or excessive sleepiness.

The study results emphasize the importance of aggressively treating insomnia in night shift workers, which may improve work productivity and safety.

The findings are detailed in the Journal of Clinical Sleep Medicine.