Rotating Night Shift May Affect Nurses’ Heart Health

Night shift work may throw off more than just your sleep cycle, especially if you switch back and forth to different shifts. In fact, a few years of this kind of schedule could hurt a nurse’s heart health.

Among female registered nurses, working a rotating night shift for 5 years or more was associated with a small increase in the risk of coronary heart disease (CHD), according to a new study in the April 26 issue of the Journal of the American Medical Association (JAMA).

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The disruption of social and biological rhythms that occur during shift work have been hypothesized to increase chronic disease risk, and evidence supports an association between shift work and coronary heart disease (CHD), metabolic disorders, and cancer. Prospective studies linking shift work to CHD have been inconsistent and limited by short follow-up.

Celine Vetter, PhD, of Brigham and Women's Hospital and Harvard Medical School, Boston, and colleagues examined the incidence of CHD in 189,158 initially healthy women followed up over 24 years in the Nurses’ Health Studies (NHS & NHS2). The NHS and NHS2 are ongoing, prospective cohort studies. The NHS began in 1976 with female registered nurses aged 30 to 55 years, and the NHS2 started in 1989 and included female registered nurses aged 25 to 42 years. Biennial follow-up questionnaires have been mailed to both groups, to update information on medical history, lifestyle factors and newly diagnosed diseases.

The researchers determined the lifetime history of rotating night shift work (three night shifts or more per month in addition to day and evening shifts) of the nurses at baseline (updated every 2 to 4 years in the NHS2).

During follow-up, 7,303 incident CHD cases (i.e., nonfatal heart attack, CHD death, angiogram-confirmed angina pectoris, coronary artery bypass graft surgery, stents, and angioplasty) occurred in the NHS and 3,519 in the NHS2. Analysis indicated that increasing years of rotating night shift work was associated with a small but statistically significant increase in CHD risk.

In the studies, the association between duration of shift work and CHD was stronger in the first half of follow-up than in the second half, suggesting waning risk after cessation of shift work. Longer time since quitting shift work was associated with decreased CHD risk among shift workers in the NHS2.

“Further research is needed to explore whether the association is related to specific work hours and individual characteristics,” the study authors wrote.

So what’s a night shift nurse to do? In an interview with CBS News, Vetter emphasized that the overall risk of CHD found in this study is very small, and said that individuals who currently work rotating night shifts should focus on reducing their heart disease risk by adjusting known lifestyle risk factors--by staying active, eating a healthy diet, maintaining a healthy body weight and quitting smoking.

Source: The JAMA Network.