Study reports that exposure to solar UVR reduces breast cancer risk

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This was a meta-analysis of 6 case-control studies that examined the relationship between solar ultraviolet radiation (UVR) exposure and breast cancer. Three of these case-control studies were also used to assess a possible dose-response relationship between solar UVR exposure and breast cancer. The study reported a statistically significant reduced risk of breast cancer with UVR exposure (relative risk, RR: 0.7, 95% confidence interval (CI): 0.65, 0.75). The study also reported a statically significant decrease in breast cancer risk as UVR exposure increased in women aged 20 to 30 years (RR: 0.92; 95% CI: 0.90, 0.95). In women over 40, the authors reported a linear dose-response relationship that for every 1000 mW/m2 hours of sunlight there is a 10% reduction in breast cancer risk. Overall, the authors report that solar UVR reduces the risk of breast cancer in women.

Exposure to solar ultraviolet radiation and breast cancer risk: A dose-response meta-analysis

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Despite the overall conclusion of the authors, when specific breast cancer subtypes were examined there was no reduced risk for estrogen receptor-negative and progesterone receptor-negative breast cancers (RR: 0.87, 95% CI:  0.67, 1.11). The study included relatively few studies (6), which limits any conclusions that can be made on the reported reduced risk of breast cancer with UVR exposure.

While this study suggests that solar UVR exposure may reduce the risk of breast cancer in women, UVR exposure remains one of the major risk factors for development of skin cancers. Skin cancer accounts for the largest number of cancers diagnosed in Australia each year (Australian Institute of Health and Welfare, 2016). In 1992 the International Agency for Research on Cancer (IARC) classified solar UVR as a Group 1 carcinogen (IARC, 1992). ARPANSA recommends that all Australians limit their UVR radiation exposure, however, if you are in the sun, it is recommended that a combination of sun protection measures is used including clothing and sunglasses, shade and sunscreen. For more information see the ARPANSA factsheet, Sun exposure and health.