The study: Led by Dr. Helen Dimich-Ward, the team studied mortality data on 58,125 registered nurses who worked in British Columbia from 1974 to 2000. Because so many of the nurses were women, the researchers did not include the few number of male RNs in the study results since their numbers were too small to be statistically viable.

The results: Registered nurses had a 39 percent lower risk of death from all causes than individuals in the general population. In addition, they had a lower risk of death from heart disease, stroke and cancer in general.

Nurses do have some vulnerability. While they enjoy greater protection from the three big killers of heart disease, stroke and most types of cancer, nurses who work in the profession at least 15 years appear to be more at risk of developing malignant melanoma, the most deadly type of skin cancer, and rectal cancer. Those who work for 25 years or more have a higher risk of breast and lung cancer, compared with those who work in nursing for five years or less.

Why? Dimich-Ward places the blame on exposure to carcinogens, such as radiation and certain drugs, as well as the health dangers associated with shift work. "Further investigations are needed to determine whether increased cancer risk among female RNs can be attributed to occupational exposures," the researchers conclude.

The study findings were published in the American Journal of Industrial Medicine.