Graveyard Shift Is Aptly Named
People who work irregular schedules, including occasional overnight (graveyard) shifts, are putting immense strain on their bodies and immune systems. And according to Harvard Medical School researchers, this sort of erratic work schedule puts the body into a constant state of “jet lag”. If you’ve ever traveled by jet across three or more time zones, you’ll be familiar with the feeling. Jet lag is a constellation of symptoms related to disruptions to the body’s circadian rhythm.
Circadian rhythm is the body’s 24-hour cycle that’s determined by light. It includes a host of carefully orchestrated signals and processes that regulate everything from body temperature and immune system activity to sleep, attentiveness, and hunger. When suddenly shifted by changing time zones, some of these systems go into a tailspin. Symptoms of mild jet lag usually involve sleepiness at inappropriate times, trouble concentrating, irritability, loss of appetite, nausea, chills, and lack of energy.
Researchers have long noted a link between working night shifts and an increased risk of certain cancers. They suspect that many of the crucial repair and maintenance activities of the immune system, which occur during sleep, may be impaired by working at night and sleeping during the day. The sleep-inducing hormone, melatonin, is highly sensitive to light. If light is present the pituitary gland does not release normal amounts of this hormone. While melatonin helps usher in sleep, it also plays important antioxidant roles in the brain and body. Some investigators suspect that disruptions in the natural release of melatonin may explain the greater risk of cancer experienced by night shirt and rotating-shift workers.
Recently, Harvard investigators examined data from the longterm Nurses’ Health Study. They discovered that nurses who had worked rotating shifts for five years or less—meaning they worked at least three night shifts a month—experienced a “modest” increase in all-cause and cardiovascular disease mortality, compared to nurses who only worked day shift. Nurses who worked more than 15 years of rotating shifts experienced an even greater risk of disease, including a significant increase in the risk of lung cancer.
If nothing else, this underscores the often-overlooked importance of keeping a regular sleep schedule. Experts suggest sleeping in a cool room with absolutely no artificial light. This means no TVs, smartphones, e-readers, or other light-emitting digital devices. Even a nightlight may be counterproductive, especially if it features blue-wavelength light, which can interfere with the production and release of melatonin.
Gu F, Han J, Laden F, et al. Total and Cause-Specific Mortality of U.S. Nurses Working Rotating Night Shifts. American Journal of Preventive Medicine. 2015