Rotating shift work and risk for prostate cancer


There have been suggestions in the past that people who work shifts, cycling between day and night work, may be at higher risk for various cancers than people who do regular daytime work. There is strong evidence that this is the case with respect to breast cancer — based on data from large numbers of nurses and airline stewardesses. However, with respect to prostate cancer good data from large study populations has been almost non-existent.

Now we have data from a large German study (by Hammer et al.), involving nearly 28,000 male, industrial production workers at a single, large chemical company who worked for that company for a period of at least 1 year between 1995 and 2005. The high quality of the company’s personnel data (on employees’ ages, on shift work, on occupational tasks, and on duration of employment) could be correlated closely to additional data from the records of the company’s occupational health service. New cases of cancer in the period 2000–2009 could also be ascertained from the state cancer registry.

Here is what Hammer et al. were able to show:

  • The total male, production employee database involved 27,828 men during the study time frame.
    • 12,609 men (45.3 percent) were rotating shift workers (whose median year of birth was 1960).
    • 15,219 men (54.7 percent) were normal daytime workers (whose median year of birth was 1959).
  • 337 new cases of prostate cancer were identified among these 27,828 men through 2009.
    • 146 cases occurred in the rotating shift workers (11.6 cases per thousand shift workers).
    • 191 cases occurred in the normal daytime workers (12.5 cases per thousand daytime workers).
  • Compared to the normal daytime workers, the rotating shift workers exhibited no increase in risk for prostate cancer (hazard ratio [HR] = 0.93).

However,

  • Compared to the general male population in Germany (a standardized incidence rate [SIR] of 1.00), men working in the industrial production side of the company did have an increase risk for diagnosis with prostate cancer.
    • For the rotating shift workers, SIR = 1.44.
    • For the normal daytime workers, SIR = 1.51.
  • There were some differences between the groups that could be observed when the cancers were identified by tumor stage, but these differences were not statistically significant.
  • Men who worked at the company for 30 years or longer had a significantly higher risk for diagnosis with prostate cancer than those with shorter employment histories (but this could be purely age-related effect).

The authors conclude that:

In this well-documented, large-scale cohort study, the incidence of prostate cancer among shift workers did not differ from that among daytime workers.

The “New” Prostate Cancer InfoLink would note that this study appears to be the largest and best documented of any of the studies of this type to date, and thus provides strong evidence in support of the authors’ conclusion.

One Response

  1. Interesting. A good part of my 27-year Navy career in special intelligence communications was working shifts.

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