Shift Work Linked to Organ Disease

The human body works according to a 24-hour sleep/wake cycle, or circadian rhythm, which controls body temperature, sleep and wake timing and the way organs and body systems work together. Researchers have long suspected that by disrupting this natural rhythm, shift work can take a toll on worker health and raise the risk for various health problems.

The University of Toronto research team, which was headed by Dr. Michael Sole and included researchers from the Peter Munk Cardiac Centre at the University Health Network, found that coordination of the many circadian clocks throughout the body is critical for normal, healthy organs. The long-term disruption of these rhythms, researchers said, ultimately can result in heart and kidney disease.

“As researchers, we accept that biological clocks and their rhythms are important for health, but there are virtually no experimental data demonstrating a casual link between circadian dysregulation and organ pathology,” said researcher and University of Toronto professor Martin Ralph. “We knew that circadian rhythm disruption had been linked with reduced longevity so we decided to try and find out where, why and how longevity is compromised.”

The study results were recently published in the Journal of American Physiology.

Schedule Changes: A Healthy Start

A separate review, led by a Durham University researcher in England, examined data from 26 shift-work studies and suggests that making simple schedule adjustments may promote health and help shift workers strike a better balance between work and personal life.

According to the review, many shift workers have frequently changing schedules. For example, instead of working a permanent night shift, some workers might work at night for several days and then rotate to working afternoons for several days. But this study shows that forward-rotating shifts that follow the logical order of the day may be easier on the body and less damaging to worker health.

“A forward rotation would be a shift in the morning, then the afternoon and then maybe a night shift later. That is less harmful to people’s health than starting at night,” said lead researcher Clare Bambra, Ph.D., a professor in Durham University’s geography department.

The review also found that rotating workers through shift changes more quickly, such as every 3 to 4 days versus every 7 days, is better for health and work-life balance. Giving employees more control over their schedules may also result in health improvements.

Despite this evidence, employers might be slow to make a change. “I think employers may want to know these changes didn’t have big costs associated with them and they were not particularly disruptive,” Bambra said.

Alec Davidson, an assistant professor with the Neuroscience Institute at Morehouse School of Medicine in Atlanta who studies circadian rhythms in animals, added that most organizations have yet to establish or adopt best practices regarding shift work. “If anything, I think there is a huge amount of resistance,” he said.

“You’d think there would be motivation to fix these things,” he added. “Substance abuse, sickness and health – as well as the happiness of the workforce – are bottom-line issues for companies if they could overcome these problems.”

Davidson said the review findings, such as the less harmful effects of forward-rotating shifts, coincide with his own research. He added that human studies with a much longer follow-up should be conducted to better understand the long-lasting health outcomes of shift work.

“Anything in moderation our bodies tend to tolerate, but abuse over the long term – we just don’t know,” he said.

The review will appear in the May issue of American Journal of Preventative Medicine.

For more information on shift work’s connection to disease, read WHO Study Links Night Shift Work, Firefighting to Cancer.