This study didn't directly connect health problems and night-shift work, but experts said it does start to help them understand why sleep might have such a powerful influence on a person's health.
"This study suggests that mistimed sleep can alter circadian rhythms, so the cycling of many, many genes is impaired," said Dr. Mark Wu, assistant professor of neurology, medicine, genetic medicine and neuroscience at Johns Hopkins University. "What this could cause, they can't really say -- except it's probably not good." Wu was not involved in the new research.
Genes carry the instructions for making proteins. Proteins make up just about every kind of chemical signal, hormone and tissue in the body, the researchers said.
The timing of when proteins are made is important because their production should correspond to our behaviors, said Frank Scheer, a neuroscientist at Harvard and director of the Medical Chronobiology Program at Brigham and Women's Hospital in Boston.
When the body anticipates a meal, for example, the liver has to stop releasing into the blood the carbohydrates it has stored and the pancreas has to make more insulin, while the muscles have to become more sensitive to insulin that's released so they can take in blood sugar, Scheer said.
"If these processes are working in concert and they're synchronized to when you eat and when you fast, then the system is very efficient and effective at absorbing these sugars quickly and minimizing any adverse consequences of elevated blood sugar levels," Scheer said.
"If these are not rhythmic, then you can easily imagine that, during the nighttime, you have this machinery up and running without need," he said. "During the daytime, when you actually do need it, it's only running half speed."