Two separate studies that were recently released are providing new evidence to the harm that working on night shift can do to women’s overall health. One study conducted in Europe has shown that night and alternating shifts increase the risk of miscarriage, menstrual disruption and infertility issues, while a study out of Canada has revealed that women who have worked night shifts for thirty years or more have twice the risk of developing breast cancer.
The first study was conducted out of the University of Southampton and was reported to the European Society of Human Reproduction and Embryology. It was the result of a compilation of data that had been published between 1969 and early 2013, and compared the health data of women who worked traditional work schedules to the data on women who had worked non-traditional schedules such as night shifts or mixed shifts. There were nearly 120,000 women’s records included in the meta-data from which the analysis was made.
The analysis showed that those women who worked a mixtue of non-traditional shifts experienced a 33% higher rate of menstrual disruption than those working traditional shifts, and an 80% increased risk of suffering issues of infertility. Women who strictly worked night shifts, with no other shifts mixed in did not have difficulty conceiving or menstrual disruption, but did have a higher rate of miscarriage, something that was not seen in women who worked mixed shifts.
According to Dr. Linden Stocker of the University of Southampton, “Whilst we have demonstrated an association between shift work and negative early reproductive outcomes, we have not proven causation. In humans, the long-term effects of altering circadian rhythms are inherently difficult to study. As a proxy measure, the sleep disruption demonstrated by the shift workers in our study creates short and long-term biological disturbances. Shift workers adopt poor sleep hygiene, suffer sleep deprivation, and develop activity levels that are out-of-sync with their body clock. However, if our results are confirmed by other studies, there may be implications for shift workers and their reproductive plans. More friendly shift patterns with less impact on circadian rhythm could be adopted where practical – although the optimal shift pattern required to maximize reproductive potential is yet to be established.”
Dr. Linden stresses that not all of the outcomes that she studied were necessarily a result of shift work, and that other factors might have been involved in the outcomes in her report. She points out that it’s possible that “completely different causes underlie menstrual dysfunction, miscarriage and subfertility. This may explain why the effects of different types of shift work are seen in some groups of women but not others.” That being said, there is the possibility that the impact that shift wok has on the women’s circadian rhythms may have an effect on changes in “clock genes” that determine biological functionality.
The Canadian study was reported in the journal Occupational and Environmental Medicine and is the result of research that followed nearly 2,500 women in Vancouver, British Columbia and Kingston, Ontario. Approximately half of the women had been diagnosed with breast cancer and the other half had not, but all were of the same age. All of the women had spent many years of their lives working outside of the home in a variety of different jobs, and they were asked to answer a questionnaire regarding whether and when they had ever worked shift work patterns during the course of their entire working career.
The study found that roughly one out of every three of the women had worked night shifts at some point in their career, and this was true of both those who had been diagnosed with breast cancer and those who had not. In assessing the association between working night shift and being diagnosed with breast cancer, the researchers found nothing to show that those who had worked nights for up to fourteen years, nor those who had worked nights between fifteen and twenty nine years, showed any increased risk for developing breast cancer. However, those who had worked nights for thirty years or more showed a dramatic increase in risk, and were statistically twice as likely to develop breast cancer as women who had never worked a night shift.
The study was conducted in follow up to a previous study that had identified a similar risk, but that study had only involved women who were working night shifts in the nursing field. This study negated the theory that nursing might have had something to do with the risk of being diagnosed with breast cancer, as it showed that the doubled risk found in those who had worked night shift for thirty years or more was true of women who worked night shift in a number of different occupations.
As more and more evidence is found about the negative impact of shift work on women’s health, medical science is trying to find counters to its effect. Though it can be difficult for those who do shift work to stay physically active, and the hours can often make one feel too fatigued to exercise, it has been shown that exercise can help make daytime sleep more restful and assist in the transition between shifts. It also has the added benefit of helping shift workers to remain more alert and less fatigued when they are working at night.
Shift work can also be difficult on social relations with partners and children. It can be difficult to get to household chores when the family is asleep, and family activities generally occur during the day when shift workers should be sleeping. This creates an additional burden, and more sleep deprivation, which can cause additional health problems.