From The Ergoweb® Learning Center

New Research Discovers Peril for Workers in Popular Split-Shift Pattern

Research on circadian rhythms and sleep deprivation fingers overnight shifts as a health-and-safety gamble, and a new study

suggests that consequences can be even worse when shifts are split. In a recent study reported in New Scientist magazine,

Josephine Arendt, a chronobiologist, described the split pattern as “a killer.”

It describes a rotation of seven night shifts, followed by seven day shifts, and it’s a popular choice. Workers prefer the

split because they are already adapted to night sleeping when they return home. The new research suggests it is the worst of

all rotations for worker health, and increases the risk of heart disease, diabetes and other metabolic disorders. Arendt and

her team at the University of Surrey in England and psychologist Andrew Smith and colleagues at Cardiff University in Wales

arrived separately at this conclusion in a pair of reports commissioned by the Health and Safety Executive (HSE), a British

government body that regulates workplace safety.

The teams compared the physiological and psychological health of several shift patterns on a group of 45 men who work on oil

rigs. These installations function as excellent natural laboratories, according to the researchers, because they offer

controlled conditions for work, rest, sleep and meals. The teams compared the two main shift schedules, which operate on a

two-week tour of duty. One was split. The other was a simple 12-hour shift, with workers staying on night shifts or day

shifts for the full two weeks.

The “splitters” fared the worst. Their urine tests revealed that levels of melatonin, the sleep-regulating hormone normally

secreted at night, did not become synchronized to the new sleep times after shift changes. They were more tired and less

attentive on the job, compared to the day shift or adapted workers, and had abnormally high levels of fatty acids circulating

in their blood after meals.

The HSE studies build on earlier research that underlines the inherent risks in overnight work. A study by Circadian

Technologies reported in Business Week quantifies the problem. It concludes that obesity, diabetes and heart disorders are

higher for night workers, that they have a 20 percent greater chance of being involved in a severe accident and make five

times more serious mistakes than their daytime counterparts.

While the health-and-safety issues of the night shift have long been known, no one appears to be calling for its abolition.

How could many industries and essential services function without 24-hour operations? Most research appears to be directed at

ameliorating the ill effects.

One of several studies cited in The Ergonomics Report