NIOSH Training for Nurses on Shift Work and Long Work Hours

Sleep and the Immune System

Scientific evidence is building that sleep has powerful effects on immune functioning.⁴ Studies show that sleep loss can affect different parts of the immune system, which can lead to the development of a wide variety of disorders (see Figure 2.2 on the next page).

For example, a modest amount of sleep loss (restricting the time allowed for sleep to 4 hours for one night) reduced natural killer (NK) cell activity to an average of 72%, compared with NK cell activity in participants who had a full night’s sleep (Figure 2.2, arrow 1).⁵ Research indicates that NK cells have a substantial role in killing tumor cells. Reduced functioning of NK cells was associated with a 1.6 times higher risk of dying with cancer (all sites) in an 11-year follow-up survey.⁶

In a similar way, restricting sleep to 4 hours for one night led to the generation of inflammatory cytokines^a, which play an important role in the development of cardiovascular and metabolic disorders (Figure 2.2, arrow 2).⁷

Sleep loss is also related to a higher risk for infection. Restricting sleep to 4 hours per night for 6 days, followed by sleep for 12 hours per night for 7 days, resulted in a greater than 50% decrease in production of antibodies to influenza vaccination, in comparison with subjects who had regular sleep hours (Figure 2.2, arrow 3).⁸

^aInflammatory cytokines are protein molecules secreted by immune and other types of cells that signal other cells to promote inflammation.