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A Retrospective Cohort Study of Mortality and Cancer Incidence among Registered Nurses in British Columbia

June 2006

Principal Investigator: Helen Ward (University of British Columbia)
Co-investigators:

Kay Teschke, Pam Ratner (University of British Columbia); Nhu Le, John Spinelli, Richard Gallagher (BC Cancer Agency)

For more information about this project, please contact Dr. Helen Ward.

Disclaimer

Issue

In the course of their work, registered nurses (RNs) may be exposed to a wide range of physical, chemical and biological hazards, including carcinogens such as antineoplastic agents and ionizing radiation. This study examined the risk of cancer for B.C. RNs compared with the overall B.C. population and for specific nursing job categories and estimated exposures.

Key findings

  • Overall, female RNs had a lower risk of mortality from all causes and of cancer incidence compared to the female population in B.C.
  • Within the cohort, the risk of breast cancer, lung cancer, malignant melanoma and rectal cancer for female RNs increased with number of years worked.
  • Compared with the male B.C. population, male RNs had a lower risk of death and no elevated risk of cancer incidence.

Objectives

  • To determine whether RNs in B.C. had a greater risk of cancer incidence or mortality compared with the B.C. population
  • To determine whether some job categories or estimated exposures to specific carcinogens were associated with a higher risk.

Method

This was a retrospective cohort study of over 58,000 RNs who were members of the Registered Nurses Association of British Columbia (RNABC) for at least one year between 1974 and 2000.

A telephone survey of experienced nurses at all 113 hospitals and health centres in B.C. was conducted to assist with exposure assessment. The survey was used to gather information on whether specific agents were used during a given year between 1974 and 2000 in certain hospital departments, as well as the likelihood of exposure by employment status and the types of exposure control measures that were used.

RNABC records were linked with the Canadian Mortality Data Base, the National Cancer Registry, and Health Canada’s National Dose Registry files by Statistics Canada. Identifying information was then removed from the files.

Cancer mortality and incidence rates were calculated for the nurses in the cohort and compared with the rates for the B.C. population. Rates were also compared within the cohort based on number of years worked within specific job categories and likelihood of exposure to a specific agent.

Results

  • Female RNs had lower rates of mortality and cancer incidence overall, when compared to the general B.C. female population.
  • Malignant melanoma was the only significantly elevated risk of cancer incidence for female RNs compared to the female population in B.C.
  • Lung cancer incidence for female RNs was one-half that of the B.C. female population.
  • Female RNs who worked a greater number of years had higher risks of breast cancer, lung cancer, malignant melanoma and rectal cancer compared with other nurses in the cohort.
  • Male RNs had a low risk of death from all cancers and had no significantly elevated rates compared with the male population in B.C.
  • Although these results must be interpreted with caution, RNs who worked in some job categories had higher risks for certain cancers compared with the rest of the cohort, including:
    • Maternal newborn or paediatric nursing departments
    • Medical/surgical specialty nursing departments
    • Gerontology
    • Cancer centre or oncology
  • Exposure to sources of ionizing radiation, as determined through survey-based estimates, was also associated with a higher risk for some cancers.

Conclusions

The association between number of years employed as an RN and specific cancers suggests that some aspects of nursing may be hazardous. Although certain job categories were associated with higher risks for some cancers, this must be interpreted with caution as estimates are based on a small number of cases and significant findings could be due to chance.

Future directions

Further research is needed to confirm these findings, and to examine the effects of additional hazards such as rotating shift and night work. Additional research is also needed to explore risks for other adverse health outcomes.