Shift work, irregular sleeping patterns 'increase stroke risk'
Workers who punch in for graveyard or rotating shifts are at increased risk of strokes, experts warn.
Using an animal model, Professor David Earnest from the Texas A&M Health Science Center College of Medicine in the United States, and his team assert that people who work shifts may have more severe stroke outcomes, in terms of both brain damage and loss of sensation and limb movement than control subjects 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," he noted, adding that some 15 million Americans don't work the typical nine-to-five day.
According to the report, it is not necessarily the longer hours, or odd schedules, 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 to maintain natural cycles.
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.
The researchers found that shift work can affect the brain and lead to more severe ischemic strokes which occur when blood flow is cut off to part of the brain.
"The body is synchronised 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," Professor Earnest explained.
"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."
Of interest, the study - supported by the American Heart Association - found that men and women show major differences in the degree to which the stroke was exacerbated by sleep cycle rhythm disruption. For instance, in male the gravity of stroke outcomes in response to shift work schedules was much worse than in females.
The scientists plan to further explore whether inflammation is a key link between circadian rhythm disruption and increased stroke severity.
In the meantime, Professor Earnest suggests that those with irregular sleeping patterns should at try to maintain regular mealtimes, in addition to avoiding the usual cardiovascular risk factors like a high-fat diet, inactivity and smoking.
The study was published in the journal Endocrinology.