Night shift work and risk of aggressive prostate cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort.

BACKGROUND: Night shift work may acutely disrupt the circadian rhythm, with possible carcinogenic effects. Prostate cancer has few established risk factors though night shift work, a probable human carcinogen, may increase the risk. We aimed to study the association between night shift work and chlorinated degreasing agents (CDAs) as possible endocrine disrupters in relation to aggressive prostate cancer as verified malignancies. METHODS: We conducted a case-cohort study on 299 aggressive prostate cancer cases and 2056 randomly drawn non-cases in the Norwegian Offshore Petroleum Workers cohort (1965-98) with linkage to the Cancer Registry of Norway (1953-2019). Work history was recorded as years with day, night, and rollover (rotating) shift work, and CDA exposure was assessed with expert-made job-exposure matrices. Weighted Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for aggressive prostate cancer, adjusted for education and year of first employment, stratified by 10-year birth cohorts, and with 10, 15, and 20 years of exposure lag periods. RESULTS: Compared with day work only, an increased hazard of aggressive prostate cancer (HR = 1.86, 95% CI 1.18-2.91; P-trend = 0.046) was found in workers exposed to ≥19.5 years of rollover shift work. This persisted with longer lag periods (HR = 1.90, 95% CI 0.92-3.95; P-trend = 0.007). The exposure-hazard curve for a non-linear model increased linearly (HRs ≥1.00) for 18-26 years of rollover shift work. No association was found with CDA exposure. CONCLUSIONS: Long-term exposure to rollover shift work may increase the hazard of aggressive prostate cancer in offshore petroleum workers.

Ultraviolet radiation and risk of cutaneous melanoma and squamous cell carcinoma in males and females in the Norwegian Offshore Petroleum Workers cohort.

BACKGROUND: Increased risk of cutaneous melanoma and squamous cell carcinoma (SCC) has been reported among petroleum workers, but few studies include females, exposure data on ultraviolet radiation (UVR), and potential confounding factors. We aimed to examine UVR exposure in relation to risk of melanoma and SCC among male and female offshore petroleum workers. We also examined the association between UVR exposure and melanoma (Breslow) thickness. METHODS: The Norwegian Offshore Petroleum Workers (NOPW) cohort (n = 27,917) holds information on sunbathing, indoor tanning, sunburns, sunscreen use, and other lifestyle factors recorded in 1998. Linkage to the Cancer Registry of Norway gave information on cancer diagnosis through 2017. We used Cox and logistic regression to estimate hazard ratios (HRs) of skin cancer and odds ratios (OR) of thick (≥1 mm) melanomas, respectively, with 95% confidence intervals (CIs). RESULTS: Melanoma risk increased with increasing frequency of sunbathing after age 20 (ptrend = 0.031), sunburn average intensity (ptrend = 0.028), and sunscreen use (HR = 2.16; 95% CI: 1.42 -3.27 for almost always vs. never/rarely). The risk of thick melanoma was inversely associated with sunbathing frequency after age 20 (OR = 0.38; 95% CI: 0.16 - 0.90 for ≥4 weeks/year vs. 1 week/year). SCC risk increased with increasing frequency of indoor tanning after age 20 (HR = 2.72; 95% CI: 1.22 - 6.05 for ≥3 times/months vs. never), sunburn average intensity (ptrend < 0.001), and sunscreen use (ptrend < 0.001). CONCLUSIONS: Our results support associations between UVR exposure and skin cancer risk in male and female offshore petroleum workers. This occupational group may be especially relevant for targeted sun protection advice.

The Inverse Relationship between 25-Hydroxyvitamin D and Cancer Survival: Discussion of Causation.

Cancer mortality rates vary inversely with geographic latitude and solar ultraviolet-B doses. This relationship may be due to an inhibitory role of vitamin D on cancer development. The relationship between vitamin D and cancer appears to be stronger for studies of cancer mortality than incidence. Because cancer mortality reflects both cancer incidence and survival, the difference may be due to effects of vitamin D on cancer survival. Here we review analytic epidemiologic studies investigating the relation between vitamin D, measured by circulating levels of 25-hydroxyvitamin D (25-OHD), and cancer survival. A relationship between low 25-OHD levels and poor survival is shown by most of the reviewed studies. This relationship is likely to be causal when viewed in light of most criteria for assessing causality (temporality, strength, exposure-response, biological plausibility and consistency). A serum level of 25-OHD around 50 nmol/L appears to be a threshold level. Conversely, there are several mechanisms whereby cancer could lower serum levels of 25-OHD. The severity of disease at the time of diagnosis and time of serum sampling are key factors to clarify the temporal aspect of these relationships. Evidence that vitamin D supplementation could retard the disease process or prolong survival time would be key evidence, but is difficult to generate. However, recent clinical trial results in prostate cancer support a role for vitamin D in this regard.