This means that the natural circadian, or daily, rhythms of your biological clock are constantly wrestling with your work schedule if you are required to work during the hours when your body and brain would normally be resting. Circadian rhythms are, in part, tied to the 24-hour cycle of the Earth's rotation and the amount of daylight to which you're exposed. The researchers believe that the higher rate of sleep disturbances, gastrointestinal and cardiovascular diseases, and accidents that shift workers experience may be due to the stress that the frequent changing of sleep and awake periods places on the body's nervous system. Max Hirshkowitz, PhD, director of the Baylor College of Medicine sleep research center in Houston, says that the biological clock is a strong force in determining people's sleep habits. For most people, it's more difficult to sleep during the day.
Light is a stimulant.
There is more noise during the day. Your biological clock tells you that the sleepiest time of the day is 4 a.m., Hirshkowitz says, yet many shift workers drink coffee around that time to stay awake. It's equivalent to drinking coffee after dinner. Shift workers often develop odd or destructive habits like trying to change their sleep habits on the weekends because they want to be with their friends. According to Hirshkowitz, this is the wrong thing to do.