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Elsewhere on the WebHarvard's Medical Chronobiology Programhttp://sleep.med.harvard.edu/ext/medical_chronobiology/Body's Biological clock found to affect cardiac rhythm patterns in healthy adultshttp://www.biology-online.org/articles/bodys_biological_clock_affect.html
Should working or playing odd hours come with a warning label? Maybe it should now that a new study is showing how living outside "normal" hours is hard on your body. A small study of ten people has shown that when their sleep/wake schedule was inverted, their blood samples quickly showed symptoms that — left untreated — could lead to diabetes, obesity and cardiovascular disease.
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For years, scientists have seen a link between odd hours and health-threatening conditions such as diabetes and cardiovascular disease, but, according to Frank Scheer of Boston's Brigham and Women's Hospital and Harvard Medical School, "The underlying mechanism was not well understood."
"What we wanted to know," says Scheer, was if living hours opposite from your internal body clock "would lead to physiological changes that may in the long run lead to increased risk for obesity, diabetes and cardiovascular disease."
Scheer and Steven Shea, also with Boston's Brigham and Women's Hospital and Harvard Medical school, led a team that inverted the hours of ten volunteers over ten days. He says, "We were struck actually by the speed of the changes that we observed."
During the testing the scientists took hourly measurements of blood sugar and hormones such as leptin, which is important in regulating someone's appetite and body weight. He added, "Even within a few days we observed quite dramatic changes in all these hormone systems." The results went so far that, "three of the individuals showed blood glucose levens which were consistent with a pre-diabetic state."
In a clinical setting, ten young, healthy and normal-weight volunteers agreed to be tested over ten days. The first two were normal days where blood samples were taken and baseline blood sugar and hormone levels established. Over the next eight days the volunteers lived 28-hour days. In other words, if the normal wake time was 7 am and bed time 11 pm, then it was shifted to waking at 11 am and sleeping at 3 am on the first day, waking at 3 pm on the second and sleeping at 7 am on the third and so on until they were back to a regular day.
The researchers were very careful to minimize factors that might otherwise throw their readings off. Activity was limited and exercise not allowed. Food was controlled so they wouldn't either gain or lose weight. The schedule of events was identical on each 28-hour day. Even light was controlled so the body's internal clock wouldn't have sunlight or other bright light as a reference point to "know" that it was out of sync. The volunteers gave up very small hourly blood samples throughout the study.
Scheer, who oversaw analysis of the information said that hormone changes came rapidly. Scheer says, "The more misaligned the two systems (body clock versus the hours people were keeping) are, the larger the effect you observed. But, the changes came quickly, such that by the second day, with a misalignment of only four hours, "we already saw changes occurring," he says.
Because the test was so small and so short, the study leaves a lot more questions that need to be answered. Scheer says that, "Future studies…would be required to look at the long term affects." For example, he wonders what happens over time: Do the symptoms stay the same, get worse, or does the body adapt? Additional questions involve the impact of sunlight, or whether people have sufficiently different reactions where they might bail ot of working odd hours because they can't physically cope, while others, whose blood sugar and hormone levels don't change as much, stick with the late-late shift.
In terms of practical advice, Scheer says that based upon this small study it's a bit soon to come up with simple guidelines. But he adds, "It's probably better to have a stable night shift schedule (rather than an) erratic, changing schedule." Which means that for those who work the late shift, they should also play on a late shift, and keep the same schedule on weekends.
Besides Scheer and Shea, other investigators involved were Michael Hilton and Christos Mantzoros."
This research was published online by the "Proceedings of the National Academy of Sciences" online early edition for the week of March 3, 2009 and funded by The National Heart, Lung and Blood Institute, General Clinical Research Center, National Center for Complementary and Alternative Medicine, National Institute of Diabetes and Digestive and Kidney Diseases , and Beth Israel Deaconess Medical Center. Elsewhere on the Web:
Harvard's Medical Chronobiology Program
Body's Biological clock found to affect cardiac rhythm patterns in healthy adults