A new study published in this week’s PLoS Medicine, shows type 2 diabetes risk is increased by rotating shift work. A fairly significant proportion of the work force is involved in some kind of permanent night or rotating night shift work, thus the findings present a potential public health issue.

The researchers Frank Hu and colleagues from Harvard School of Public Health in Boston, USA, 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 concluded that :

  • NHS I : 6,165 women – more than 5% – developed type 2 diabetes
  • NHS II 3,961 women – under 4% developed type 2 diabetes

The Authors also used statistical modeling to show that the duration of the rotating night shift work was strongly linked with type 2 diabetes, increasing with the number of years worked. However, the associations weakened once other factors were taken into consideration. The study included no men or ethnic groups in its data, so would need to be confirmed using other batches of data perhaps from firefighters, police or military, nonetheless there is already enough evidence for implementing new, healthier work rotas to help employees avoid the health issue of working nights.

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.”

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) said in an accompanying article :

“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 …

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.”

It’s worth noting that that national figures for diabetes, shown on diabetes.org, state that some 8% of the US population suffer from the disease. Thus, the 4-5% for night shift workers does not on face-value seem so terrible.

However, the researchers say that the women studied, who worked rotating shifts, had a 20% increased risk versus their peers who did not work nights.

There are all kinds of other risks involved in type 2 diabetes, including diet, exercise, age, weight and sudden weight gain, it’s thus unfair to make comparisons with national figures.

Obviously the body’s time clock for sleeping is disrupted with the shift work, and this might result in insulin spikes and more stress on the pancreas. It’s also possible that those working at night in rotational shifts, may be more likely to consume higher quantities of less healthy foods, such as junk food and sugary drinks, as well as feeling washed out during the day, meaning they take less exercise.

We live in a virtually 24/7 society now, so it would be interesting to see a comparison with professions, such as entertainers who are generally up late all the time, rather than only in rotations – clearly this is going to be an ongoing issue.

Written By Rupert Shepherd