Less Melatonin, More Stress
A study involving women who served in the Danish Army between 1964 and 1999 found that working the night shift increases risk of developing breast cancer. Questionnaires that asked about work patterns were filled out by 141 women who developed breast cancer and 551 women who did not. Working at night increased the risk by 40 percent and doubled if they worked three nights a week for a minimum of six years or said they were night owls. The risk quadrupled in night shift workers who claimed to be morning people. Working at night lowers the production of a protective hormone called melatonin and raises stress. These results add to previous research that has shown a similar link. Researchers suggest adjusting the wavelength of light so it does not suppress melatonin.
Disrupts Wake-Sleep Cycle
There is growing evidence to suggest that working nights is not only linked to sleeping on the job but also to other health issues. Recently stories about air traffic controllers falling asleep on the job have brought this issue to light again but studies reveal that 30 to 50 percent of people who work nights doze off while working at least once week. Night shifts disrupt the circadian rhythm, or wake-sleep cycle that is controlled by hormones. For people on rotating shifts the brain becomes confused and not sure when it’s bedtime which ends up impairing concentration, memory and learning. Research has also shown that the risk of some chronic diseases and even cancer is increased in night workers. Shift work is now considered a “probable carcinogen” by the World Health Organization.