Shift workers are more likely to suffer severe strokes, study suggests

A welder works in a shop at night

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Some 15 million Americans who work graveyard or rotating shifts may be more prone to severe ischemic strokes, the leading cause of disability in the United States, according to new research published in the journal Endocrinology.

“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, a professor in the Department of Neuroscience and Experimental Therapeutics at the 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.”

According to Earnest, it’s not the longer hours — or the weird hours — necessarily that are 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, 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, 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.

“This research has clear implications for shift workers with odd schedules, but probably extends to many of us who keep schedules that differ greatly from day-to-day, especially from weekdays to weekends,” Earnest added. “These irregular schedules can produce what is known as ‘social jet lag,’ which similarly unwinds our body clocks so they no longer keep accurate time, and thus can lead to the same effects on human health as shift work.”

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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