The shift work schedule, especially rotating shifts, disrupts the natural 24 hour cycle of the body, thus increasing the possibility of a severe ischemic stroke.
A new study in the United States (US) has found that shift work can put workers out of sync with their body clocks, leading to more severe strokes.
Researcher David Earnest from the Texas A&M Health Science Centre College of Medicine, said that the body is synchronised to night and day by circadian rhythms and 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 is the problem. Instead, it is the change in the timing of waking, sleeping and eating every few days that 'unwinds' their 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 United States, which occur when blood flow is cut off to part of the brain. Using an animal model, the team 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.
Interestingly, their study, supported by the American Heart Association (AHA), also 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.
Researcher Farida Sohrabji added that these sex differences might be related to reproductive hormones. Young women are less likely to suffer strokes, as compared with men of a similar age, and when they do, the stroke outcomes are likely to be less severe. In females, oestrogen is thought to be responsible for this greater degree of neuro-protection.
The study is published in Endocrinology.
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