Shift Work Unwinds Body Clocks: Health Risks

News ID: 1091899 Service: Science
shift worker

TEHRAN (Tasnim) - Statistics show that some 15 million Americans don't work the typical nine-to-five. These shift workers are more prone to numerous health hazards, from heart attacks to obesity, and now, new research shows shift work may also have serious implications for the brain.

"The body is synchronized to night and day by circadian rhythms --24-hour cycles controlled by internal biological clocks that tell our bodies when to sleep, when to eat and when to perform numerous physiological processes," said David Earnest, Ph.D., professor in the Department of Neuroscience and Experimental Therapeutics at the Texas A&M Health Science Center College of Medicine.

"A person on a shift work schedule, especially on rotating shifts, challenges, or confuses, their internal body clocks by having irregular sleep-wake patterns or meal times," he explained.

According to Earnest, it's not the longer hours --or the weird hours-- necessarily that is the problem. Instead, it is the change in the timing of waking, sleeping and eating every few days that "unwinds" our body clocks and makes it difficult for them to maintain their natural, 24-hour cycle. When body clocks are disrupted, as they are when people go to bed and get up at radically different times every few days, there can be a major impact on health.

Earnest and his colleagues have found that shift work can lead to more severe ischemic strokes, the leading cause of disability in the US, which occur when blood flow is cut off to part of the brain.

Using an animal model, Earnest and his team, including colleague Farida Sohrabji, Ph.D., also a professor in the Department of Neuroscience and Experimental Therapeutics and director of the Women's Health in Neuroscience Program, found that subjects on shift work schedules had more severe stroke outcomes, in terms of both brain damage and loss of sensation and limb movement than controls on regular 24-hour cycles of day and night.

Of interest, their study --supported by the American Heart Association-- found that males and females show major differences in the degree to which the stroke was exacerbated by circadian rhythm disruption; in males, the gravity of stroke outcomes in response to shift work schedules was much worse than in females.

An immediate impact of these studies on human health is that individuals in shift work-type professions should be monitored more closely and more frequently for cardio- and cerebrovascular disease and risk factors such as hypertension and obesity.

In the meantime, Earnest suggests that those with irregular sleeping patterns should at least try to maintain regular mealtimes, in addition to avoiding the usual cardiovascular risk factors like a high-fat diet, inactivity and tobacco use.

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