Study Links Shift Work, Heart Problems

A new study says female nurses who worked irregular shifts for more than six years were up to 70% more likely than co-workers to suffer a heart attack.

The study, in today’s issue of the American Heart Assn. journal Circulation, was done by a team at Harvard Medical School and written by Dr. Ichiro Kawachi, an assistant professor of medicine.

“Shift work is a type of stress,” he said. “If you disrupt the body’s daily biological clock, the body responds by pouring out stress-related hormones . . . and these things generally do bad things for the body.”

Kawachi said “rotating night shifts also are associated with reduced job-related performance and higher levels of perceived stress.”

The study focused on nursing because it is one of the few professions in which a large number of women work night shifts.

In 1976, the Harvard team began tracking more than 121,000 female nurses, ages 30 to 55, who were free of diagnosed heart disease or stroke. In 1988, researchers asked them how many years they had worked rotating night shifts, which was defined as at least three night shifts each month in addition to day and evening shifts.

The risk was highest among women who were still working rotating shifts; it dropped to 50% when women no longer doing shift work were added in.