Saturday, March 7, 2009

Working the Night Shift May Be Hazardous to Your Health

Working nights takes its toll on the body. Night shift workers are at a higher risk for accidents and sleep disorders, as well as digestive problems. Many experience increased psychological stress resulting from issues unrelated to work such as family and personal obligations that often interfere with a night worker’s sleep schedule. Although most people require 8 hours of sleep to obtain sufficient rest, many night workers seldom manage to achieve it. And, because our body's sleep cycle is based upon light and dark, night workers must battle against their natural sleep tendencies.

Scientific evidence has now shown that the disruption of the body’s internal clock, or circadian rhythms, may lead to hormonal and metabolic changes that increase risks for obesity, diabetes and heart disease. The full report can be found in the Proceedings of the National Academy of Sciences.

The report authors note that about 8.6 million Americans perform shift work, including factory workers, hospital staff, policemen, firefighters, pilots, road crews and truck drivers. Shift work is defined by the National Sleep Foundation as any type of schedule that falls outside the standard nine-to-five norm for business hours.

According to study author Frank Scheer, an instructor of medicine in the division of sleep medicine at Brigham and Women's Hospital and Harvard Medical School, “In the long run, the physiological impact of shift work on several markers involved in the regulation of body weight (such as) leptin, insulin, (and) cortisol, seems to contribute to the increased risk for the development of diabetes, cardiovascular disease and obesity.”

The researchers conducted a laboratory test simulating the effects of jet lag (or the lasting impact of regular shift work). The study participants were five men and five women who followed a constantly changing sleeping and eating schedule for a period of eight days. During this period, all participants ate and slept within all phases of the circadian cycle by following an artificially created schedule of 28 hours.

The results of the experiment revealed that circadian misalignment caused a drop in levels of leptin, a hormone that of regulates weight. According to the researchers, decreasing leptin levels could cause an increase in appetite coupled with a reduction in activity and may lead to possible acceleration of the onset of obesity and heart disease. In addition, findings showed the occurrence of changes in blood sugar and insulin levels, which resulted in weakened glucose tolerance and reduced insulin sensitivity. In fact, three study participants having no prior history of diabetes were found to have developed glucose levels similar to those of pre-diabetic people as well as elevated daytime blood pressure levels.

The peak of hormonal change was noted during periods when participant schedules were a full 12 hours off the normal sleep-wake cycle, meaning that they were scheduled to sleep during the day and remain awake throughout the night.

Scheer warned that although the findings of the study are compelling, more research is needed to determine the weight of the results. He noted that the in-laboratory study was of short duration and acknowledged, “we don't yet know if circadian misalignment has a similar impact in the long run in a real-life setting where people are performing night shift work.”

Scheer also pointed out the need to study how various people respond to night shift work differently. He explained, “Because shift work typically affects people's alertness levels, and GI functioning, and those who don't cope well with this are likely to drop out. Which means that those who continue with this kind of work might not be so susceptible to such problems, and may be less sensitive to this kind of misalignment. These are all questions for the future.”