Women who work outdoors may be less likely to develop breast cancer

COPENHAGEN, Denmark — Breast cancer is the most common form of the disease in the U.S., with one woman diagnosed every two minutes. Research now suggests that a woman’s career choice could play a role in her risk for the disease. According to a recent study, women who work outdoors are less likely to develop breast cancer.

Scientists say gardening, walking the dog and exercising outside has been shown to expose people to vitamin D that can help to ward off infection and cancer. The powerful health benefits of sunlight have been shunned in recent years due to concerns about skin cancer and the increasing use of computers for both work and leisure. Scientists from the Danish Cancer Society and the University of Copenhagen, however, believe the rising incidence of breast cancer over the last half of the 20th century may be due to vitamin D deficiency.

The researchers identified 38,375 women under the age of 70 who had been diagnosed with primary breast cancer from the Danish Cancer Registry. They compared each of them with five women born in the same year and randomly selected from the Danish Civil Registration System. Full employment history was retrieved from pension fund records, and a job exposure matrix was used to assess each woman’s occupational exposure to sunlight.

After taking account of potentially influential factors, such as reproductive history, no association emerged between occupational exposure to sunlight and overall breast cancer risk. However, long term occupational exposure was associated with a lower risk of breast cancer after the age of 50.

In these women, occupational exposure for 20 or more years was associated with 17 percent lower odds of a breast cancer diagnosis, while the highest level of cumulative exposure was associated with 11 percent reduced odds. Researchers say there was no information on dietary vitamin D intake and lifestyle factors in the study. Another theory suggests the effect of sunlight on circadian rhythm, as sun exposure can increase melatonin peak levels during sleep which may have cell boosting effects.

“This is the first study exploring the association between occupational ultraviolet ray exposure and breast cancer using objective lifetime employment history,” the authors write.  “This is likely a more accurate indicator of actual exposure than cross sectional ambient measures, and a more reliable measure of long-term exposure than self-reports. This study indicates an inverse association between long-term occupational [sunlight] exposure and late-onset breast cancer. This finding needs further attention in future occupational studies.”

The study is published in British Medical Journal’s Occupational and Environmental Medicine.

SWNS writer Joe Morgan contributed to this report.