Your stroke risk climbs if you work weird hours

Source: Christina Sumners – Texas A&M,, June 2, 2016

People who work rotating shifts or who change sleeping and eating schedules often are more likely to have a severe stroke, a new study finds.

It’s not the longer hours—or the weird hours—that necessarily seem to be the problem, according to David Earnest, a professor at the Texas A&M Health Science Center College of Medicine. Instead, it’s the change in the timing of waking, sleeping, and eating every few days that “unwinds” body clocks and makes it difficult to maintain a natural, 24-hour cycle.

“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,” says Earnest.

When body clocks are disrupted, as they are when people go to bed and get up at radically different times every few days, it takes a toll on health.

Earnest and his team found that shift work schedules were linked to more severe stroke outcomes, in terms of both brain damage and loss of sensation and limb movement, based on research with animal models.

They also found 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.
Sex Differences in the Impact of Shift Work Schedules on Pathological Outcomes in an Animal Model of Ischemic Stroke
Source: David J. Earnest, Nichole Neuendorff, Jason Coffman, Amutha Selvamani, and Farida Sohrabji, Endocrinology, First Published Online: June 2, 2016
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From the abstract:
Circadian clock desynchronization has been implicated in the pathophysiology of cardiovascular disease and related risk factors (e.g., obesity, diabetes). Thus, we examined the extent to which circadian desynchronization exacerbates ischemic stroke outcomes and whether its detrimental effects on stroke severity and functional impairments are further modified by biological sex. Circadian entrainment of activity rhythms in all male and female rats was observed during exposure to a fixed light:dark (LD) 12:12 cycle but was severely disrupted when this LD cycle was routinely shifted (12hr advance/5d) for ≈ 7 weeks. In contrast to the regular estrous cycles in fixed LD animals, cyclicity was abolished and persistent estrus was evident in all shifted LD females. The disruption of estrous cyclicity in shifted LD females was associated with a significant increase in serum estradiol levels relative to that observed in fixed LD controls. Circadian rhythm disruption exacerbated stroke outcomes in both shifted LD male and female rats and further amplified sex differences in stroke impairments. In males, but not females, circadian disruption after exposure to the shifted LD cycle was marked by high rates of mortality. In surviving females, circadian desynchronization following exposure to shifted LD cycles produced significant increases in stroke-induced infarct volume and sensorimotor deficits with corresponding decreases in serum IGF-1 levels. These results suggest that circadian rhythm disruption associated with shift work schedules or the irregular nature of our everyday work and/or social environments may interact with other non-modifiable risk factors such as biological sex to modulate the pathological effects of stroke.