Many Iowans who work nights or a swing shift are chronically sleep deprived. For those people who work the night shift, there’s no way for their bodies to ever really adjust. Sleep expert doctor Mark Mahowald says one reason is because our biological clocks rely on daylight. He says another reason is — they tend to keep one foot in the real world on weekends and holidays and so the idea of having one’s biological clock completely adjust to night shift hours is erroneous. It doesn’t happen. Because of that Mahowald says shift workers are chronically sleep-deprived. And while there are no associated long term medical problems, it can lead to impaired function and workplace accidents. He sites examples like: Exxon Valdez, Challenger, Three Mile Island, those were allofficially attributed to errors in judgment in the workplace due to sleepiness. About 20 percent of workers in all industrialized nations work irregular hours. Mahowald’s advice for night shift workers includes maintaining a regular sleep schedule and avoiding things like alcohol, tobacco and heavy meals around bedtime.