The ruling overturned a year-old lower court decision that awarded the worker compensation for his "shiftwork sleep disorder," a condition triggered by irregular work hours that consists of symptoms of insomnia and fatigue.

A Nova Scotia Court of Appeals judge ruled that the worker's inability to adapt to shiftwork was a "personal characteristic" neither caused or aggravated by job requirements.

Court decisions in the U.S. also have favored employers in cases involving shiftwork sleep disorder, which is recognized by the American Psychiatric Association. If the Canadian shiftworker wins an appeal, it could cost Canadian employers thousands of dollars and influence similar cases south of the border in the U.S., says Jennifer Allen of Circadian Technologies, Inc.