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When Your Body Clock Resets

Adjusting to the Nightshift (1:19)

Daniel Cohen, MD, MMSc, formerly of Harvard, tells how to adjust your internal clock to working at night.

Your body clock adjusts to schedule changes. This process moves slowly, however. After switching between day work and night work, for example, most people find it takes several days to feel as alert and sleep as soundly as they usually do. Changing work and sleep times by several hours may disrupt bodily functions, making you wake up from sleep more often than usual to use the bathroom or feel hungry at odd hours.

People who maintain the same schedules on work days and days off usually have a predictable internal "day" and "night." Working regularly in daytime or evening hours means they often are able to sleep at the same time seven days a week. Those who work at night seldom manage to do that. 

Railroaders and others who work irregular hours often find it hard to stay in sync—their body clocks are constantly being reset. Despite daily exposure to daylight and darkness, they may fight sleepiness when awake, and find it difficult to fall asleep or stay asleep when they want to sleep. They have to organize their days carefully to stay alert in waking hours, and to get the sleep they need. 

"The hard part is getting rest in the middle of the day or the early evening. We know that we should be resting, but we are not tired and we can't sleep." 
- Mark Kramer, locomotive engineer