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Rotating night-shift work is associated with increased risk of Type 2 diabetes in women

PLOS

In women, there is a positive association between rotating night shift work and the risk of developing type 2 diabetes and, furthermore, long duration of shift work may be associated with greater weight gain. These findings from a study by Frank Hu and colleagues from Harvard School of Public Health in Boston, USA, published in this week's PLoS Medicine, are of potential public health significance as a large proportion of the working population is involved in some kind of permanent night and rotating night shift work.

The authors used data from the Nurses' Health Study I (NHS I - established in 1976, and which included 121704 women) and the Nurses' Health Study II (NHS II - established in 1989, and which included 116677 women), and found that in NHS I, 6,165 women developed type 2 diabetes and in NHS II 3,961 women developed type 2 diabetes. Using statistical models, the authors found that the duration of rotating night shift work was strongly associated with an increased risk of type 2 diabetes in both cohorts and that the risks of women developing type 2 diabetes, increased with the numbers of years working rotating shifts. However, these associations were slightly weaker after the authors took other factors into consideration.

Although these findings need to be confirmed in men and other ethnic groups, these findings show that additional preventative strategies in rotating night shift workers should therefore be considered.

The authors say: "Recognizing that rotating night shift workers are at a higher risk of type 2 diabetes should prompt additional research into preventive strategies in this group."

In an accompanying Perspective article, Mika Kivimäki from University College London, David Batty from the University of Edinburgh, and Christer Hublin from the Finnish Institute of Occupational Health in Helsinki, Finland (uninvolved in the research study) say: "We are increasingly residing in a '24/7' society, thus the option to eradicate shift working is not realistic. If the observed association between rotating shift work and [type 2 diabetes] is causal, as it may be, additional efforts to prevent [type 2 diabetes] among shift workers through promotion of healthy life styles, weight control and early identification and treatment of prediabetic and diabetic employees are needed."

These authors continue: "Some modifications to shift work itself might also be feasible. Rotating shift work comprises a range of alternative schedule patterns, such as backward- and forward-rotating shift systems, and the proportion of night and early morning shifts varies. Future studies should address these variations and identify patterns that minimize [type 2 diabetes] risk, ideally through large-scale randomized trials that would provide insights into causality."

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Article by Frank Hu and colleagues

Funding: The study was supported by the National Institutes of Health grant (DK58845, CA55075, CA87969, CA50385). Dr. Sun was supported by a career development award K99HL098459 from the National Heart, Lung, and Blood Institute. Dr. Schernhammer was supported by R01HL103607 grant from National Heart, Lung, and Blood Institute. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

Citation: Pan A, Schernhammer ES, Sun Q, Hu FB (2011) Rotating Night Shift Work and Risk of Type 2 Diabetes: Two Prospective Cohort Studies in Women. PLoS Med 8(12): e1001141. doi:10.1371/journal.pmed.1001141

CONTACT:

Frank Hu

Harvard School of Public Health
665 Huntington Avenue
Dept. of Nutrition, HSPH
Boston, MA 2115
USA
+1 617-432-0113
frank.hu@channing.harvard.edu

Perspective by Mika Kivimäki, David Batty and Christer Hublin

Funding: MK is supported in part by National Institutes of Health grants HL036310 and AG034454. GDB is a Wellcome Trust Fellow. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

Citation: Kivimäki M, Batty GD, Hublin C (2011) Shift Work as a Risk Factor for Future Type 2 Diabetes: Evidence, Mechanisms, Implications, and Future Research Directions. PLoS Med 8(12): e1001138. doi:10.1371/journal.pmed.1001138

CONTACT:

Mika Kivimäki

University College London
Department of Epidemiology and Public Health
1-19 Torrington Place
London WC1E 6BT
United Kingdom
m.kivimaki@ucl.ac.uk

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