Scitech | Shift workers at risk

Research finds disturbing body clock results in poor health outcomes

Researchers have found evidence that disturbances in regular sleeping and activity patterns affect the regulation of hormones, leading to increased risk of diabetes, obesity, and heart disease. These findings have important implications for the health and well-being of those who undergo chronic misalignment of their internal clock due to night shift work.

Disturbing the circadian rhythm – the body’s biological clock – results in a decrease of the regulatory hormone leptin, according to findings published earlier this month in the Proceedings of the National Academy of Sciences. The study used controlled conditions to simulate misalignment of the body’s internal clock: subjects were awake at night, asleep during the day, and ate on an inverted time schedule. The findings affirmed prior studies, but pinpointed disturbances in the circadian rhythm rather than sleep deficiency alone as a cause of the health consequences.

The paper’s lead author, Dr. Frank Scheer, a neuroscientist at Harvard Medical School, spoke about the short time interval in which changes were observed.

“What is remarkable is that it only took a few days of misalignment to cause the changes we saw,” Scheer said. Within three days, three of the eight subjects experienced prediabetic states (increased insulin tolerance and glucose levels) in response to meals. Increased hunger and appetite were also observed due to low leptin levels, which in the long term could lead to the development of obesity. In particular, when a person’s internal body clock was misaligned, the level of cortisol, a hormone related to stress, increased waking blood pressure and decreased sleep efficiency.

A recent study by Statistics Canada found that in 2005 about 2.3 million Canadians aged 19 to 64 worked rotating shifts (those that change irregularly from days to evenings or to nights) or had irregular schedules. According to the Canadian Centre for Occupational Health and Safety, the increasingly 24/7 nature of the service industry has lead to increases in shift work among emergency workers, health care workers, and security personnel.

Contracted security guards at McGill for example, who may be employed as foot patrollers or dispatchers, can work night shifts from 9 p.m. to 5 a.m. or from 11 p.m. to 7 a.m. for an entire month, followed by a month of day shifts.

Bita Eslami, Coordinator of the Immigrant Workers’ Centre in Montreal, pointed to the pervasiveness of shift work among employed immigrants.

“[For] anyone in factory work, textile work, hard labour, or domestic work, chances are they will have had to do night shifts,” Eslami said.

The study finds that night shift work may also impair cognitive abilities.

According to Scheer, cognitive impairment is twice as likely to occur when one wakes up during the biological night as opposed to when one is normally awaken – a key concern for emergency and health care personnel.

“We rely on [health care workers], that they can make the best judgment they can, which is not as good as it could be,” Scheer said.

According to Michelle Dennis, Communication Coordinator for the Canadian Nurses Association, nurses’ work environment is also often not conducive to night shifts.

“Usually there is no place provided for nurses to sleep during their breaks,” Dennis wrote in an email to The Daily. She also noted that understaffing has an impact on nurse fatigue, which may compromise nurses’ health and patients’ safety.

Scheer pointed to two additional aspects of shift work that have negative consequences for health.

“Their daily commute, during which they are exposed to sunlight…prevents them from readjusting,” Scheer said. “The other aspect is that on their days off, workers switch to normal sleep – wake to spend time with their friends, family, or go shopping, which prevents them from adjusting to their night work.”

What can be done to ease the effects of misalignment due to night shifts? According to Scheer, working under bright lights and keeping to a single daily schedule would help shift the body clock.

“Rotational shifts are most hard to adjust to…. There’s no way for [the] bio clock to adjust, and the whole story repeats each time,” said Scheer.

The study was co-authored by Frank Scheer, Michael Hilton, Christos Mantzoros, and Steven A. Shea.


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