Shift workers have low serotonin, poorer sleep

Last Updated: Thursday, August 2, 2007 | 4:04 PM ET

CBC News

Rotating shift workers tend to have lower levels of the feel-good hormone serotonin, leading to disturbed sleep patterns, suggests new research.

Researchers at the University of Buenos Aires studied 683 men of self-reported European ancestry, comparing 437 day workers to 246 rotating shift workers. Day and night work periods started at 6 a.m. and 6 p.m.

Lack of high-quality sleep can sabotage job performance, make people less alert and put them at risk of an injury on the job.
CBC

All of the subjects stuck to the same schedule throughout the study, which is in the Aug. 1 issue of the journal Sleep.

Shift workers' serotonin levels, measured through blood tests, were much lower than the levels of workers on regular day schedules, found the study, led by Carlos Pirola.

Shift workers were also found to have greater hip-to-waist ratios, higher cholesterol  and insulin levels, increased blood pressure and higher triglyceride levels.

Low levels of serotonin are associated with conditions such as anger, depression and anxiety.

Previous studies have found rotating and night shift work affect the cardiovascular and metabolic systems, suggesting that shift work may be directly responsible for increased body fat and higher blood pressure levels, said the authors of the Buenos Aires study.

Because serotonin governs sleep patterns, among other body functions, the authors theorize that shift work also leads to so-called shift work sleep disorder. People with the disorder tend to remain awake when they should be sleeping. But during waking hours, they may be severely tired.

Shift workers in the study typically slept one to four hours less than average, and experienced a poor quality of sleep.

Lack of high-quality sleep can sabotage job performance, make people less alert and put them at risk of an injury on the job, researchers said.