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Shift workers, sleep-deprived have increased risk of heart disease

Not getting a good night's sleep can result in a number of problems including poor concentration, weight gain, and a greater likelihood of accidents. For shift workers and individuals who experience chronic sleep deprivation, new research suggests insufficient sleep could also increase the risk of heart disease.

A study in the American Heart Association's journal Hypertension found that lack of sleep or not having a set sleep schedule could cause the body's involuntary processes to malfunction, leading to an increased risk of cardiovascular disease.

To test how circadian rhythm disturbances can impact heart function, researchers altered the sleep patterns of 26 healthy individuals. Participants were restricted to five hours of sleep for eight days with either a set bedtime, known as circadian alignment, or bedtimes delayed by 8.5 hours for four of the eight days, known as circadian misalignment.

Researchers discovered that both groups had an increased heart rate during the day, which grew worse at night for participants in the circadian misalignment group. Both groups also experienced an increase in urinary excretion of the stress hormone norephinephrine, which can constrict blood vessels, raise blood pressure and expand the windpipe. Activity of the vagal nerve, which is related to heart rate variability during deeper sleep phases and has a restorative effect on cardiovascular function, was also decreased in both groups.

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"In humans, as in all mammals, almost all physiological and behavioral processes, in particular the sleep-wake cycle, follow a circadian rhythm that is regulated by an internal clock located in the brain," said Daniela Grimaldi, M.D., Ph.D., lead author and a research assistant professor at Northwestern University, said in a press release. "When our sleep-wake and feeding cycles are not in tune with the rhythms dictated by our internal clock, circadian misalignment occurs."

Insufficient sleep is a public health problem according to the Centers for Disease Control and Prevention. The problem is particularly common in shift workers, who make up 15 to 30 percent of the working population in industrialized countries.

"Our results suggest shift workers, who are chronically exposed to circadian misalignment, might not fully benefit from the restorative cardiovascular effects of nighttime sleep following a shift-work rotation," Grimaldi said in a press release.

More sleep is the best solution, but for those who can't avoid shift work, the researchers suggest countering the negative effects of disruptive sleep by maintaining a healthy diet and exercise.

Grimaldi and colleagues plan on continuing the research by studying whether people exposed to sleep loss -- with or without circadian misalignment -- are able to recover once they get consecutive days of good sleep.

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