Former epidemiological studies have indicated that solar ultraviolet B radiation (UV) may reduce the risk of prostate cancer, however, the evidence is inconclusive. To contribute with evidence, the present study aimed to evaluate the association between occupational UV exposure and prostate cancer in Danish men.
A total of 12,268 men diagnosed with primary prostate cancer before age 70 were identified via the Danish Cancer Registry. The Danish Civil Registration System was used to randomly select five male controls matched on year of birth, alive and free of prostate cancer at the time of diagnosis of the index case. Full individual-level employment history was retrieved from the Danish Supplementary Pension Fund Register and linked to a job exposure matrix to assess occupational UV exposure. Conditional logistic regression was used to estimate odds ratios (ORs) with corresponding 95 % confidence intervals.
We observed an inverse association between ever exposure to occupational UV and prostate cancer (OR=0.93, 95 % CI: 0.89–0.97). Longer duration of exposure (≥20 years: OR=0.90, 95 % CI: 0.84–0.96) and highest cumulative exposure (OR=0.90, 95 % CI: 0.84–0.96) were both inversely associated with disease risk.
The present study indicates a modest protective effect from occupational UV exposure on the risk of prostate cancer. This finding needs further attention in future large-scale studies.
- • Solar ultraviolet B radiation (UV) may reduce the risk of a number of chronic diseases, including prostate cancer.
- • The effect of occupational UV exposure on prostate cancer risk was explored by using registry-based employment
- • The study indicates that UV is associated with a modest decreased risk of prostate cancer.
- • Spending short daily periods of time in the sun may by recommended for indoor male workers.
Prostate cancer is the most common cancer among men in most countries worldwide . Both incidence and mortality rates are strongly associated with higher age, however, other firmly established risk factors are few and include Black ethnicity and family history of prostate cancer . Other factors suspected to also play a role in prostate cancer development include physical inactivity, dietary factors, e.g. consumption of meat and dairy products , and night-shift work . In addition, geographical trends in incidence rates of prostate cancer have been observed; Scandinavians have higher incidence of the disease compared with residents in southern Europe and a similar difference in disease rates between men residing in Northern vs. Southern geographical areas in the US has been reported as well . Analogous observations have been reported for a number of other cancers, e.g. breast and colon cancer, and may reflect a protective effect of ultraviolet B radiation (UV) on cancer risk. It is theorized that protection from certain cancers could be provided by UV exposure through a vitamin D -mediated mechanism . Vitamin D is initially formed from 7-dehydrocholesterol after UV exposure of the skin and UV-mediated synthesis is the major source of obtainment in most countries, although ingestion of vitamin D from supplementation or the diet, e.g. fatty fish, is also considered important sources . Vitamin D is first hydroxylated in the liver forming the prohormone, 25-Hydroxyvitamin D (25-OHD), and then again to the most hormonally active form, 1,25(OH) 2 D, in the kidneys . However, it has been shown that prostate cells can synthesize 1,25(OH) 2 D intracellularly from circulating serum 25-OHD and that prostate cells respond to 25-OHD levels by promoting differention of cells together with inhabitation of proliferation, invasiveness and metastasis .