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Shift work is “less harmful to health” than thought

Think that modern working patterns, like night shifts, are bad for your health? A new study suggests that might not be the case.

Image: Assunta Del Buono/John Birdsall/Press Association Images

NIGHT SHIFTS HAVE made the headlines of late for being harmful to health, and even having the potential to cause cancer.

But a new study suggests that it might not be as disruptive as you would think.

A team from Queen’s University, Kingston, Ontario, Canada, studied the effect of shift work on nurses who worked rotating shifts.

Dr Kristan Aronson (Community Health and Epidemiology), Dr Joan Tranmer (School of Nursing), Dr Harriet Richardson (Community Health and Epidemiology), Anne Grundy (Community Health and Epidemiology) and Dr Charles Graham (Biomedical and Molecular Sciences) studied 123  nurses who worked two 12 hour days, two 12 hour nights and then had five days off.

They equipped the nurses with a light data logger and the nurses also provided urine and saliva samples.

The researchers found that melatonin production did not differ much between the women whether they worked day or night shifts.

However, women who worked at night were exposed to more light than those working during the day.

But the peak melatonin levels and the change in melatonin levels was similar no matter what shift was worked.

It was found that when the data taken during the night shift was analysed, there was an inverse relationship between how much light the women were exposed to, and how much melatonin was produced.

But when the data from the day and night shifts was combined, there was no association between light exposure and melatonin levels.

This showed that melatonin exposure is not strongly related to how much light workers are exposed to.

In a previous study on 61 nurses that the team also took part in, it was found that nurses who worked during the day slept for an average of 8.27 hours, while those working at night slept for 4.78 hours.

There was no significant correlation between sleep duration and melatonin, and no consistent relationship between physical activity and melatonin.

The melatonin levels indicated that the circadian rhythms of night workers were not altered, which showed that two nights of rotating shift work may not change the timing of melatonin production.

In 2007, the International Agency for Research on Cancer (IARC) added night shift work to a list of ‘probable’ carcinogens, below the group 1 category of items such as asbestos and engine exhaust.

In Denmark, compensation was paid by the government to 38 women who developed breast cancer after working night shifts for long periods of time.

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