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

Abstract

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.

Prostate cancer in workers exposed to night-shift work: two cases recognized by the Korean Epidemiologic Investigation Evaluation Committee

“… 16 Another study reported that the risk of aggressive prostate cancer was significantly increased in the group with more than 19.5 years of rotating shifts (HR: 1.86; 95% CI: 1.18–2.91). 38 2) Consistency: Increased risk of prostate cancer in night-shift workers has been consistently observed in several epidemiological studies of various population and work schedules. 16 28 29 30 31 32 3) Temporality: The 2 workers were diagnosed with prostate cancer after doing night shift work for 17 and 35 years, respectively.…”

“…4) Biological gradient: Exposure-response curves using non-linear model showed a linear increase in risk of aggressive prostate cancer with 18–26 years of rollover shifts. 38 5) Plausibility: The biological mechanism was provided by the results of studies confirming the effects of light and dark schedule changes on immunosuppression, chronic inflammation, and cell proliferation 23 24 25 and also increased risk of cancer incidence was reported in animal studies. 20 6) Coherence: This epidemiological association between night-shift work and prostate cancer does not contradict natural history and biology of prostate cancer.…”

“…Exposure-hazard curves using non-linear model showed a linear increase in risk with 18–26 years of rollover shifts. 38 …”

“… 14 15 A well-designed case-control study reported that night work increased the risk of prostate cancer, especially the risk of prostate cancer with high Gleason scores supported by recently published case-cohort study. 16 38 Based on the scientific evidences, the Epidemiologic Investigation Evaluation Committee recognized 2 cases in 2020 and 2021 based on the association between night-shift work and prostate cancer. These 2 cases have expanded the scope of industrial accident compensation for prostate cancer related to night-shift work.…”

Risk of prostate cancer with increasing years of night shift work: A two-stage dose-response meta-analysis with duration of night shift work as exposure dose

“…For outcome classification, most studies used all prostate cancer cases regardless of their stage. However, three cohort reports (from two cohort studies) used only aggressive stages [ 28 , 37 ]. In addition, one cohort study used mortality due to prostate cancer as the outcome instead of the incidence [ 38 ].…”