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."