Shift work is a staple of hospital nursing, and several large studies have found that rotating night shifts, in particular, are associated with increased mortality. Now, an international group of researchers has found evidence of significant harm to nurses' overall health from rotating night shifts.

Published in the May issue of JAMA Network Open, the study by Shi and colleagues found that 10 or more years of night shift work-defined as at least three nights per month in addition to day and evening shifts-conferred 20% decreased odds of healthy aging. The study's end point for healthy aging was reaching age 70 without major chronic disease, physical limitations, memory impairment, and mental health issues. The association between a history of night shift work and deteriorated health was unchanged when age, body mass index, or lifestyle factors were considered. Although the mechanisms underlying these effects are unknown, the authors pointed to several possibilities, including altered circadian rhythms since they are important to metabolic regulation and disruptions may impair physical health.

The researchers' findings were based on responses from 46,318 women ages 46 to 68 years who were enrolled in the Nurses' Health Study and were free of major chronic diseases at this cohort study's baseline in 1988. The analysis of cognitive decline, added later to the definition of healthy aging, was based on a cohort of 14,273 nurses. To evaluate overall health status, the researchers relied on participants' responses to questionnaires about chronic illnesses, their physical and memory function, and mental health.

Limitations of the study include that participants' mean age was about 55 years-a time when few were continuing or beginning night shift work-and that most were White and female. The authors recommend additional studies, using cohorts with greater racial and ethnic representation as well as men, to test the findings in a population more representative of today's nurse workforce.-Gail M. Pfeifer, MA, RN