Trial sheds less light on nurses working night shift

Improved job performance, quality of sleep
By Sarah Dobson
|Canadian HR Reporter|Last Updated: 09/08/2010

The potential downsides to shift work are increasingly being publicized — sleep disturbance, risk of injury, reduced productivity and more serious health concerns such as cancer and cardiovascular disease. What’s less understood is the actual reason behind the occupational hazards. What exactly is it about shift work that causes the problems?

Nurses at Western Toronto Hospital were treated to a first-hand look last year when they participated in a field trial to test special glasses during night shifts. The filters block light in the 470 to 480 nanometre range, which is thought to be the wavelength that suppresses melatonin (a hormone secreted at night that maintains the body’s circadian rhythm and may act indirectly or directly in causing cancer), said Robert Casper, a senior scientist at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto who was involved with the trial.

There are 1,500 genes in the body that have a 24-hour rhythm and all of these are disrupted by inappropriate light exposure at night, which could be related to obesity, insulin activity or cancer, he said. The glasses can restore melatonin secretion, while also preventing a rise in cortisol, a stress hormone that is normally low at night but rises in the day, he said.