People who are employed as shift workers are more prone to numerous health problems from heart attacks to obesity and now a new study finds their risk of severe stroke may be elevated as well.

Statistics show that some 15 million Americans don't work the typical nine-to-five. These are employees (or shift workers), who punch in for graveyard or rotating shifts.

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 bodily processes. Shift work disrupts this internal clock, note researchers at the Texas A&M College of Medicine in Bryan, Texas

The research team performed an animal study and found that the animals on simulated shift work schedules suffered more severe stroke outcomes, in terms of both brain damage and loss of sensation and limb movement than controls subjects that were on regular 24-hour cycles of day and night.
   
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, according to lead author Dr. David Earnest.

They also found that the male subjects showed much more severe stroke outcomes than the female subjects, which they hypothesized might be a due to a protective effect from estrogen, according to the study, which appears in Endocrinology.