Night work and prostate cancer risk: results from the EPICAP Study

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

Introduction

Night shift work could be a modifiable risk factor for prostate cancer. However, the epidemiological evidence is inconsistent. To summarize the existing evidence on this topic, we conducted a two-stage dose-response meta-analysis.

Methods

Medical librarians searched PubMed, EMBASE, and the Cochrane Library on December 30, 2022. Seven criteria were used to determine the inclusion of each study in the present analysis.

Results

Eleven cohort studies (12 cohort reports; total cases: 9366; and total person-years: 88,238,009) and seven case-control studies (seven case-control reports; total cases: 5593; and total controls: 6876) were included. This study estimated that the risk of prostate cancer increased by 1, 12, 24, and 39% after 1, 10, 20, and 30 years of night shift work exposure, respectively, according to four cohort and five case-control studies.

Discussion

Seven inclusion criteria were used to determine which studies were eligible for this analysis. Risk ratios from cohort studies and odds ratios from case-control studies were analyzed separately. However, all odds ratios from the case-control studies were excluded because of a high likelihood of publication bias. Moreover, exposure, measured in years of night shift work, was defined based on the information provided by individual studies. Finally, we utilized a recently reported two-stage dose-response meta-analysis method. This study provides evidence that night shift work contributes to the risk of prostate cancer in a dose-dependent manner.

A review for the impacts of circadian disturbance on urological cancers

Circadian rhythm is an internal timing system and harmonizes a variety of cellular, behavioral, and physiological processes to daily environment. Circadian disturbance caused by altered life style or disrupted sleep patterns inevitably contributes to various disorders. As the rapidly increased cancer occurrences and subsequent tremendous financial burdens, more researches focus on reducing the morbidity rather than treating it. Recently, many epidemiologic studies demonstrated that circadian disturbance was tightly related to the occurrence and development of cancers. For urinary system, numerous clinical researches observed the incidence and progress of prostate cancer were influenced by nightshift work, sleep duration, chronotypes, light exposure, and meal timing, this was also proved by many genetic and fundamental findings. Although the epidemiological studies regarding the relationship between circadian disturbance and kidney/bladder cancers were relative limited, some basic researches still claimed circadian disruption was closely correlated to these two cancers. The role of circadian chemotherapy on cancers of prostate, kidney, and bladder were also explored, however, it has not been regularly recommended considering the limited evidence and poor standard protocols. Finally, the researches for the impacts of circadian disturbance on cancers of adrenal gland, penis, testis were not found at present. In general, a better understanding the relationship between circadian disturbance and urological cancers might help to provide more scientific work schedules and rational lifestyles which finally saving health resource by reducing urological tumorigenesis, however, the underlying mechanisms are complex which need further exploration.

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

Background

In 2019, the International Agency for Research on Cancer re-evaluated the carcinogenicity of night-shift work and reported that there is limited evidence that night-shift work is carcinogenic for the development of prostate cancer. Therefore, in 2020 and 2021, the Korean Epidemiologic Investigation Evaluation Committee concluded that 2 cases of prostate cancer were occupational diseases related to the night-shift work. Here, we report the 2 cases of prostate cancer in night-shift workers which were first concluded as occupational diseases by the Korean Epidemiologic Investigation Evaluation Committee.

Case presentation

Patient A: A 61-year-old man worked as a city bus driver for approximately 17 years, from 2002 to 2019, and was exposed to night-shift work during this period. In March 2017, the patient was diagnosed with high-grade prostate cancer through core-needle biopsy after experiencing stinging pain lasting for 2 months. Patient B: A 56-year-old man worked as an electrician and an automated equipment operator in a cement manufacturing plant for 35 years from 1976 to 2013 and was exposed to night-shift work during this period. In 2013, the patient was diagnosed with high-grade prostate cancer through core needle biopsy at a university hospital because of dysuria that lasted for 6 months.

Conclusions

The 2 workers were diagnosed with high-grade prostate cancer after working night shifts for 17 and 35 years respectively. Additionally, previous studies have reported that high-grade prostate cancer has a stronger relationship with night-shift work than low or medium-grade prostate cancer. Therefore, the Korean Epidemiologic Investigation Evaluation Committee concluded that night-shift work in these 2 patients contributed to the development of their prostate cancer.

Circadian Clock Dysregulation and Prostate Cancer: A Molecular and Clinical Overview

Circadian clock dysregulation has been implicated in various types of cancer and represents an area of growing research. However, the role of the circadian clock in prostate cancer has been relatively unexplored. This literature review will highlight the potential role of circadian clock dysregulation in prostate cancer by examining molecular, epidemiologic, and clinical data. The influence of melatonin, light, night shift work, chronotherapy, and androgen independence are discussed as they relate to the existing literature on their role in prostate cancer.

Association between Outdoor Light at Night and Prostate Cancer in the Health Professionals Follow-up Study

BACKGROUND

Circadian disruption is a potential risk factor for advanced prostate cancer, and light at night (LAN) exposure may disrupt circadian rhythms. We evaluated whether outdoor LAN increases the risk of prostate cancer.

METHODS

We prospectively followed 49,148 participants in the Health Professionals Follow-up Study from 1986 through 2016. We estimated baseline and cumulative time-varying outdoor LAN with ∼1 km2 resolution using data from the US Defense Meteorological Satellite Program's Operational Linescan System, which was assigned to participants' geocoded addresses. Participants reside in all 50 U.S. states and reported a work or home address. We used multivariable Cox models to estimate HRs and 95% confidence intervals (CI) for the association between outdoor LAN and risk of overall (7,175 cases) and fatal (915 cases) prostate cancer adjusting for individual and contextual factors.

RESULTS

There was no association between the interquartile range increase in cumulative LAN and total (HR, 1.02; 95% CI, 0.98-1.06) or fatal (HR, 1.05; 95% CI, 0.96-1.15) prostate cancer in adjusted models. However, there was a positive association between baseline LAN and total prostate cancer among non-movers (HR, 1.06; 95% CI, 1.00-1.14) including among highly screened participants (HR, 1.11; 95% CI, 1.01-1.23).

CONCLUSIONS

There was a suggestive positive association between baseline outdoor LAN and total prostate cancer. Additional studies with different measures of outdoor LAN and in more diverse populations are necessary.

IMPACT

To our knowledge, this is the first longitudinal cohort study exploring the relationship between outdoor LAN and prostate cancer.

Unmasking the Hidden Danger: A Decade-Long Systematic Review of Case-Control Studies on Single Occupational Risks and Prostate Cancer

The present systematic review addresses the influence of occupational exposures on prostate cancer risk. Eleven studies were analyzed for a range of occupational exposures, including but not limited to firefighting, physical activity, night shift work, chemical exposure, and solar ultraviolet radiation. The results of the review reveal that firefighters exposed to harmful substances, individuals engaged in physically strenuous work, and workers with chronic night shift routines showed an increased likelihood of developing prostate cancer. Moreover, the review identified an increased risk associated with exposure to certain chemicals, including alkylphenolic compounds and benzene-related substances. The evidence underscores the importance of considering the cumulative effect of multiple risk factors in a comprehensive risk assessment. However, the conclusions indicate the necessity for further research to deepen these relationships and develop more effective strategies for the prevention of prostate cancer.

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.

Understanding Sleep Disturbances in Prostate Cancer-A Scientometric Analysis of Sleep Assessment, Aetiology, and Its Impact on Quality of Life

Prostate cancer is the most commonly diagnosed cancer in the United Kingdom. While androgen-deprivation therapy is the most common treatment for prostate cancer, patients undergoing this treatment typically experience side effects in terms of sleep disturbances. However, the relation between prostate cancer and sleep and the way in which sleep interventions may benefit oncological patients is underinvestigated in the literature. The current study aims to review in a data-driven approach the existing literature on the field of prostate cancer and sleep to identify impactful documents and major thematic domains. To do so, a sample of 1547 documents was downloaded from Scopus, and a document co-citation analysis was conducted on CiteSpace software. In the literature, 12 main research domains were identified as well as 26 impactful documents. Research domains were examined regarding the link between prostate cancer and sleep, by taking into account variations in hormonal levels. A major gap in the literature was identified in the lack of use of objective assessment of sleep quality in patients with prostate cancer.

The association between night shift work and breast cancer risk in the Finnish twins cohort

Breast cancer is highly prevalent yet a more complete understanding of the interplay between genes and probable environmental risk factors, such as night work, remains lagging. Using a discordant twin pair design, we examined the association between night shift work and breast cancer risk, controlling for familial confounding. Shift work pattern was prospectively assessed by mailed questionnaires among 5,781 female twins from the Older Finnish Twin Cohort. Over the study period (1990-2018), 407 incident breast cancer cases were recorded using the Finnish Cancer Registry. Cox proportional hazards models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) adjusting for potential confounders. Within-pair co-twin analyses were employed in 57 pairs to account for potential familial confounding. Compared to women who worked days only, women with shift work that included night shifts had a 1.58-fold higher risk of breast cancer (HR = 1.58; 95%CI, 1.16-2.15, highest among the youngest women i.e. born 1950-1957, HR = 2.08; 95%CI, 1.32-3.28), whereas 2-shift workers not including night shifts, did not (HR = 0.84; 95%CI, 0.59-1.21). Women with longer sleep (average sleep duration > 8 h/night) appeared at greatest risk of breast cancer if they worked night shifts (HR = 2.91; 95%CI, 1.55-5.46; P_intx=0.32). Results did not vary by chronotype (P_intx=0.74). Co-twin analyses, though with limited power, suggested that night work may be associated with breast cancer risk independent of early environmental and genetic factors. These results confirm a previously described association between night shift work and breast cancer risk. Genetic influences only partially explain these associations.

Circadian rhythm in prostate cancer: time to take notice of the clock

The circadian clock is an evolutionary molecular product that is associated with better adaptation to changes in the external environment. Disruption of the circadian rhythm plays a critical role in tumorigenesis of many kinds of cancers, including prostate cancer (PCa). Integrating circadian rhythm into PCa research not only brings a closer understanding of the mechanisms of PCa but also provides new and effective options for the precise treatment of patients with PCa. This review begins with patterns of the circadian clock, highlights the role of the disruption of circadian rhythms in PCa at the epidemiological and molecular levels, and discusses possible new approaches to PCa therapy that target the circadian clock.

Occupational heat exposure and prostate cancer risk: A pooled analysis of case-control studies

BACKGROUND

Heat exposures occur in many occupations. Heat has been linked to key carcinogenic processes, however, evidence for associations with cancer risk is sparse. We examined potential associations between occupational heat exposure and prostate cancer risk in a multi-country study.

METHODS

We analysed a large, pooled dataset of 3142 histologically confirmed prostate cancer cases and 3512 frequency-matched controls from three countries: Canada, France, and Spain. Three exposure indices: ever exposure, lifetime cumulative exposure and duration of exposure, were developed using the Finnish Job-Exposure Matrix, FINJEM, applied to the lifetime occupational history of participants. We estimated odds ratios (ORs) and 95% confidence intervals (CIs), using conditional logistic regression models stratified by 5-year age groups and study, adjusting for potential confounders. Potential interactions with exposure to other occupational agents were also explored.

RESULTS

Overall, we found no association for ever occupational heat exposure (OR 0.97; 95% CI 0.87, 1.09), nor in the highest categories of lifetime cumulative exposure (OR 1.04; 95% CI 0.89, 1.23) or duration (OR 1.03; 95% CI 0.88, 1.22). When using only the Spanish case-control study and a Spanish Job Exposure Matrix (JEM), some weakly elevated ORs were observed.

CONCLUSIONS

Findings from this study provide no clear evidence for an association between occupational heat exposure and prostate cancer risk.

Association between working hours and cancer risk in Japan: The Japan public health center-based prospective study

OBJECTIVES

In this study, we evaluated the association between working hours and cancer risk in the Japanese population, which has not been evaluated.

METHODS

Using a cohort database from a Japan Public Health Center-based Prospective Study, we evaluated 26 738 participants (16 351 men and 10 387 women), who responded to a questionnaire about working hours and followed these participants from 1993-1994 to 2013. Participants were divided into four groups according to working hours (≤6, 7-8, 9-10, ≥11 h/day). The hazard ratio (HR) and 95% confidence interval (CI) of each cancer incidence were calculated using a multivariable-adjusted Cox proportional hazard model.

RESULTS

During 488 383 person-years of follow-up, 481 patients with newly diagnosed cancers were identified. There was no clear association between long working hours and overall cancer, lung cancer, and stomach cancer risks. Long working hours tended to increase prostate cancer risk in men and breast cancer risk in women, although the difference was not statistically significant. Increased liver cancer risk with short working hours (HR [95% CI]; 3.15 [1.44-6.88] in the ≤6 h/day group vs. 7-8 h/day) was observed. Colorectal cancer also tended to increase risk in short working hours, however, there were not statistically significance.

CONCLUSIONS

In this population, long working hours were not associated with cancer risk with statistically significance. The association between short working hours and liver cancer risk was observed, probably due to the reverse causation of liver cancer.

Relationships of sleep traits with prostate cancer risk: A prospective study of 213,999 UK Biobank participants

BACKGROUND

The effect of sleep on the occurrence of prostate cancer (PCa) remains unclear. This study explored the influence of sleep traits on the incidence of PCa using a UK Biobank cohort study.

METHODS

In this prospective cohort study, 213,999 individuals free of PCa at recruitment from UK Biobank were included. Missing data were imputed using multiple imputation by chained equations. Cox proportional hazards models were used to calculate the adjusted hazard ratios and 95% confidence intervals for PCa (6747 incident cases) across seven sleep traits (sleep duration, chronotype, insomnia, snoring, nap, difficulty to get up in the morning, and daytime sleepiness). In addition, we newly created a healthy sleep quality score according to sleep traits to assess the impact of the overall status of night and daytime sleep on PCa development. E values were used to assess unmeasured confounding.

RESULTS

We identified 6747 incident cases, of which 344 died from PCa. Participants who usually suffered from insomnia had a higher risk of PCa (hazard ratio [HR]: 1.11; 95% confidence interval [CI]: 1.04-1.19, E value: 1.46). Finding it fairly easy to get up in the morning was also positively associated with PCa (HR: 1.09; 95% CI: 1.04-1.15, E value: 1.40). Usually having a nap was associated with a lower risk of PCa (HR: 0.91; 95% CI: 0.83-0.99, E value: 1.42).

CONCLUSIONS

Fairly easy to get up in the morning and usually experiencing insomnia were associated with an increased incidence of PCa. Moreover, usually having a nap was associated with a lower risk of PCa. Therefore, sleep behaviors are modifiable risk factors that may have a potential impact on PCa risk.

A practical nutritional guideline to manage neuroendocrine neoplasms through chronotype and sleep

Chronotype is the attitude of subjects to carry out their daily activities mainly in the morning ("lark") or in the evening ("owl"). The intermediate chronotype is located between these two categories. It has been demonstrated that chronotype can influence the incidence, course and response to treatments of tumors. In particular patients diagnosed with gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) and evening chronotype are characterized by unhealthy lifestyle, obesity, metabolic syndrome, a worsen cardiometabolic profile, a poor prognosis with a progressive disease and the development of metastasis. In addition, evening chronotype has been associated with sleep disturbances, which in turn have been related to tumor development and progression of tumors. There is a strict connection between sleep disturbances and NENs because of the hyperactivation of proangiogenic factors that caused aberrant neoangiogenesis. A nutritional tailored approach could represent a tool to align subjects with evening chronotype to physiological biological rhythms based on the properties of some macro and micronutrients of being substrate for melatonin synthesis. Thus, we aimed to provide an overview on the association of chronotype categories and sleep disturbances with NENs and to provide nutritional advices to manage subjects with NENs and these disturbances of circadian rhythm.

Occupation and prostate Cancer risk: results from the epidemiological study of prostate cancer (EPICAP)

Background

Although prostate cancer (PCa) is the most frequent male cancer in industrialized countries, little is known about its aetiology. The literature has suggested an influence of the environment, including occupational exposures, but results are inconsistent. In this context, we investigated PCa risk associated to employment among several occupations using data from EPICAP study.

Methods

EPICAP is a French population-based case-control study including 819 PCa incident cases and 879 controls frequency-matched on age. In-person interviews gathered data on potential risk factors and lifetime occupational histories for each job held at least 6 months. Then, occupations were coded using ISCO 68. Unconditional logistic regressions were performed to assess the association between occupations (ever occupied and by duration) and PCa risk, whether all and aggressive, after adjusting for potential confounders.

Results

For ≥10 years of employment, we found positive associations with PCa, whether overall and aggressive, among Medical, Dental and Veterinary workers (OR (odds ratios) =5.01 [95% confidence interval] [1.27; 19.77]), Members of the armed forces (OR = 5.14 [0.99; 26.71]) and Fishermen, hunters and related workers (OR = 4.58 [1.33; 15.78]); whether overall and non-aggressive PCa, among Legislative officials and Government administrators (OR = 3.30 [1.10; 9.84]) or Managers (OR = 1.68 [1.18; 2.41]); however a negative association, whether overall and non-aggressive PCa, among Material-Handling and Related Equipment Operators, Dockers and Freight Handlers (OR = 0.40 [0.17; 0.97]).

Conclusion

Excess PCa risks were observed in the EPICAP study mostly among white collar workers exposed to several factors in their work environment. These emerging associations can be used to lead future research investigating specific occupational exposures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12995-022-00346-2.

A Simulated Shift Work Schedule Does Not Increase DNA Double-Strand Break Repair by NHEJ in the Drosophila Rr3 System

Long-term shift work is widely believed to increase the risk of certain cancers, but conflicting findings between studies render this association unclear. Evidence of interplay between the circadian clock, cell cycle regulation, and DNA damage detection machinery suggests the possibility that circadian rhythm disruption consequent to shift work could alter the DNA double-strand break (DSB) repair pathway usage to favor mutagenic non-homologous end-joining (NHEJ) repair. To test this hypothesis, we compared relative usage of NHEJ and single-strand annealing (SSA) repair of a complementary ended chromosomal double-stranded break using the Repair Reporter 3 (Rr3) system in Drosophila between flies reared on 12:12 and 8:8 (simulated shift work) light:dark schedules. Actimetric analysis showed that the 8:8 light:dark schedule effectively disrupted the rhythms in locomotor output. Inaccurate NHEJ repair was not a frequent outcome in this system overall, and no significant difference was seen in the usage of NHEJ or SSA repair between the control and simulated shift work schedules. We conclude that this circadian disruption regimen does not alter the usage of mutagenic NHEJ DSB repair in the Drosophila male pre-meiotic germline, in the context of the Rr3 system.

The influence of biological and lifestyle factors on circulating cell-free DNA in blood plasma

Research and clinical use of circulating cell-free DNA (cirDNA) is expanding rapidly; however, there remain large gaps in our understanding of the influence of lifestyle and biological factors on the amount of cirDNA present in blood. Here, we review 66 individual studies of cirDNA levels and lifestyle and biological factors, including exercise (acute and chronic), alcohol consumption, occupational hazard exposure, smoking, body mass index, menstruation, hypertension, circadian rhythm, stress, biological sex and age. Despite technical and methodological inconsistences across studies, we identify acute exercise as a significant influence on cirDNA levels. Given the large increase in cirDNA induced by acute exercise, we recommend that controlling for physical activity prior to blood collection is routinely incorporated into study design when total cirDNA levels are of interest. We also highlight appropriate selection and complete reporting of laboratory protocols as important for improving the reproducibility cirDNA studies and ability to critically evaluate the results.

Effects of chronic intermittent hypobaric hypoxia on prostate-specific antigen (PSA) in Chilean miners

OBJECTIVE

The aim was to determine the effects of chronic intermittent hypobaric hypoxia (CIHH) on prostate-specific antigen (PSA) levels in Chilean miners who work at different altitudes.

METHODS

A cross-sectional study was conducted between April and July 2019. Miners from five mines (N=338) at different altitudes were evaluated. We recorded sociodemographic, working and altitude information. Haemoglobin oxygen saturation (SaO2) and haemoglobin (Hb) were measured in situ, while PSA and testosterone were analysed at a low level. Linear mixed-effect models were used to evaluate the association between PSA level and two CIHH exposures: composite CIHH (with four descriptors) and ChileStd-CIHH (CIHH Chilean standard; based on the Chilean technical guide for occupational exposure to CIHH). All models were adjusted by age, body mass index and day of the work the samples were taken.

RESULTS

Highest and lowest PSA levels were found in mines ≥3000 m above sea level (mine 3: median=0.75, IQR=-0.45; mine 4: median=0.46, IQR=-0.35). In the multilevel models, the wider altitude difference between mining operation and camp showed lower PSA levels (model D: βPSA=-0.93 ng/mL, βlogPSA=-0.07, p<0001), adjusted for other CIHH descriptors, SaO2, Hb and testosterone. The descriptors of composite CIHH explained better PSA variations than ChileStd-CIHH (model D: marginal R2=0.090 vs model A: marginal R2=0.016).

CONCLUSIONS

Occupational health regulations and high altitude medicine should consider these results as initial evidence on the inclusion of new descriptors for CIHH and the possible effect of this exposure on PSA levels in this male-dominated occupational sector.

An Analysis of the Multifaceted Roles of Heme in the Pathogenesis of Cancer and Related Diseases

Heme is an essential prosthetic group in proteins and enzymes involved in oxygen utilization and metabolism. Heme also plays versatile and fascinating roles in regulating fundamental biological processes, ranging from aerobic respiration to drug metabolism. Increasing experimental and epidemiological data have shown that altered heme homeostasis accelerates the development and progression of common diseases, including various cancers, diabetes, vascular diseases, and Alzheimer's disease. The effects of heme on the pathogenesis of these diseases may be mediated via its action on various cellular signaling and regulatory proteins, as well as its function in cellular bioenergetics, specifically, oxidative phosphorylation (OXPHOS). Elevated heme levels in cancer cells intensify OXPHOS, leading to higher ATP generation and fueling tumorigenic functions. In contrast, lowered heme levels in neurons may reduce OXPHOS, leading to defects in bioenergetics and causing neurological deficits. Further, heme has been shown to modulate the activities of diverse cellular proteins influencing disease pathogenesis. These include BTB and CNC homology 1 (BACH1), tumor suppressor P53 protein, progesterone receptor membrane component 1 protein (PGRMC1), cystathionine-β-synthase (CBS), soluble guanylate cyclase (sGC), and nitric oxide synthases (NOS). This review provides an in-depth analysis of heme function in influencing diverse molecular and cellular processes germane to disease pathogenesis and the modes by which heme modulates the activities of cellular proteins involved in the development of cancer and other common diseases.

The inhibitory effect of melatonin on human prostate cancer

Prostate cancer (PCa) is one of the most commonly diagnosed human cancers in males. Nearly 191,930 new cases and 33,330 new deaths of PCa are estimated in 2020. Androgen and androgen receptor pathways played essential roles in the pathogenesis of PCa. Androgen depletion therapy is the most used therapies for primary PCa patients. However, due to the high relapse and mortality of PCa, developing novel noninvasive therapies have become the focus of research. Melatonin is an indole-like neurohormone mainly produced in the human pineal gland with a prominent anti-oxidant property. The anti-tumor ability of melatonin has been substantially confirmed and several related articles have also reported the inhibitory effect of melatonin on PCa, while reviews of this inhibitory effect of melatonin on PCa in recent 10 years are absent. Therefore, we systematically discuss the relationship between melatonin disruption and the risk of PCa, the mechanism of how melatonin inhibited PCa, and the synergistic benefits of melatonin and other drugs to summarize current understandings about the function of melatonin in suppressing human prostate cancer. We also raise several unsolved issues that need to be resolved to translate currently non-clinical trials of melatonin for clinic use. We hope this literature review could provide a solid theoretical basis for the future utilization of melatonin in preventing, diagnosing and treating human prostate cancer.

Circadian genes polymorphisms, night work and prostate cancer risk: Findings from the EPICAP study

Over the past two decades, several studies have attempted to understand the hypothesis that disrupting the circadian rhythm may promote the development of cancer. Some have suggested that night work and some circadian genes polymorphisms are associated with cancer, including prostate cancer. Our study aims to test the hypothesis that prostate cancer risk among night workers may be modulated by genetic polymorphisms in the circadian pathway genes based on data from the EPICAP study, a population-based case-control study including 1511 men (732 cases/779 controls) with genotyped data. We estimated odds ratio (ORs) and P values of the association between prostate cancer and circadian gene variants using logistic regression models. We tested the interaction between circadian genes variants and night work indicators that were significantly associated with prostate cancer at pathway, gene and SNP levels. Analyses were also stratified by each of these night work indicators and by cancer aggressiveness. The circadian pathway was significantly associated with aggressive prostate cancer among night workers (P = .004), particularly for men who worked at night for <20 years (P = .0002) and those who performed long night shift (>10 hours, P = .001). At the gene level, we observed among night workers significant associations between aggressive prostate cancer and ARNTL, NPAS2 and RORA. At the SNP-level, no significant association was observed. Our findings provide some clues of a potential modulating effect of circadian genes in the relationship between night work and prostate cancer. Further investigation is warranted to confirm these findings and to better elucidate the biological pathways involved.

How to schedule night shift work in order to reduce health and safety risks

Objectives This discussion paper aims to provide scientifically based recommendations on night shift schedules, including consecutive shifts, shift intervals and duration of shifts, which may reduce health and safety risks. Short-term physiological effects in terms of circadian disruption, inadequate sleep duration and quality, and fatigue were considered as possible links between night shift work and selected health and safety risks, namely, cancer, cardio-metabolic disease, injuries, and pregnancy-related outcomes. Method In early 2020, 15 experienced shift work researchers participated in a workshop where they identified relevant scientific literature within their main research area. Results Knowledge gaps and possible recommendations were discussed based on the current evidence. The consensus was that schedules which reduce circadian disruption may reduce cancer risk, particularly for breast cancer, and schedules that optimize sleep and reduce fatigue may reduce the occurrence of injuries. This is generally achieved with fewer consecutive night shifts, sufficient shift intervals, and shorter night shift duration. Conclusions Based on the limited, existing literature, we recommend that in order to reduce the risk of injuries and possibly breast cancer, night shift schedules have: (i) ≤3 consecutive night shifts; (ii) shift intervals of ≥11 hours; and (iii) ≤9 hours shift duration. In special cases - eg, oil rigs and other isolated workplaces with better possibilities to adapt to daytime sleep - additional or other recommendations may apply. Finally, to reduce risk of miscarriage, pregnant women should not work more than one night shift in a week.

Night Shift Work, Chronotype, Sleep Duration, and Prostate Cancer Risk: CAPLIFE Study

To analyze the association between prostate cancer (PCa) risk and night shift work, chronotype, and sleep duration in the context of a population-based case-control study of incident prostate cancer in Spain, a total of 465 PCa cases and 410 controls were analyzed. Selection criteria were: (i) age 40-80 years, and (ii) residence in the coverage area of the reference hospitals for ≥6 months before recruitment. Exposure variables were: (i) night shift work (permanent or rotating); (ii) chronotype: morning, neither, or evening (Munich ChronoType Questionnaire) and (iii) sleep duration according to the recommendations of the American National Sleep Foundation. PCa aggressiveness was determined according to the International Society of Urology Pathology classification. Adjusted odds ratios (aOR) and 95% confidence intervals (95% CI) were estimated using logistic regression models. Night shift work was associated with PCa, aOR = 1.47 (95% CI 1.02-2.11), especially for rotating night shifts, aOR = 1.73 (95% CI 1.09-2.75). The magnitude of the association between ever night work and PCa was higher in evening subjects with aOR = 3.14 (95% CI 0.91-10.76) than in morning chronotypes with an aOR = 1.25 (95% CI 0.78-2.00). Working night shifts, especially rotating night shifts, could increase PCa risk. This risk may be higher in people with an evening chronotype.

Association Between Night-Shift Work and Cancer Risk: Updated Systematic Review and Meta-Analysis

Background: Nightshift work introduces light at night and causes circadian rhythm among night workers, who are considered to be at increased risk of cancer. However, in the last 2 years, nine population-based studies reported insignificant associations between night-shift work and cancer risks. We aimed to conduct an updated systematic review and meta-analysis to ascertain the effect of night-shift work on the incidence of cancers. Methods: Our protocol was registered in PROSPERO and complied with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Embase, PubMed, and Web of Science databases were used to comprehensively search studies published up to May 31, 2019. The random-effect model (Der Simonian-Laird method) was carried out to combine the risk estimates of night-shift work for cancers. The dose-response meta-analysis was performed to verify whether the association was in a dose-dependent manner. Results: Our literature searching retrieved 1,660 publications. Included in the meta-analyses were 57 eligible studies with 8,477,849 participants (mean age 55 years; 2,560,886 men, 4,220,154 women, and 1,696,809 not mentioned). The pooled results showed that night-shift work was not associated with the risk of breast cancer (OR = 1.009, 95% CI = 0.984-1.033), prostate cancer (OR = 1.027, 95% CI = 0.982-1.071), ovarian cancer (OR = 1.027, 95% CI = 0.942-1.113), pancreatic cancer (OR = 1.007, 95% CI = 0.910-1.104), colorectal cancer (OR = 1.016, 95% CI = 0.964-1.068), non-Hodgkin's lymph (OR = 1.046, 95% CI = 0.994-1.098), and stomach cancer (OR = 1.064, 95% CI = 0.971-1.157), while night-shift work was associated with a reduction of lung cancer (OR = 0.949, 95% CI = 0.903-0.996), and skin cancer (OR = 0.916, 95% CI = 0.879-0.953). The dose-response meta-analysis found that cancer risk was not significantly elevated with the increased light exposure of night- shift work. Conclusion: This systematic review of 57 observational studies did not find an overall association between ever-exposure to night-shift work and the risk of breast, prostate ovarian, pancreatic, colorectal, non-Hodgkin's lymph, and stomach cancers.

Shift Work and Prostate Cancer: An Updated Systematic Review and Meta-Analysis

The International Agency of Research in Cancer (IARC) has recently confirmed shift work as a type 2A carcinogen. The results presented in published epidemiological studies regarding prostate cancer are inconsistent and the association remains controversial. The aims of this study were: (a) to investigate the possible association between shift work and prostate cancer incidence, identifying possible sources of heterogeneity; and (b) to analyze the potential effect of publication bias. A search for cohort and case-control studies published from January 1980 to November 2019 was conducted. The quality of the articles was assessed using the Newcastle-Ottawa Scale. Pooled OR were calculated using random-effects models. Heterogeneity was evaluated using Cochran's Q test and data were stratified by potential sources of heterogeneity. Publication bias was analyzed. Eighteen studies were included. No association was found between rotating/night-shift work and prostate cancer, pooled OR 1.07 (95%CI 0.99 to 1.15), I2 = 45.7%, p = 0.016. Heterogeneity was eliminated when only cohort studies (pooled OR 1.03; 95%CI 0.96 to 1.10; I2 = 18.9%, p = 0.264) or high-quality studies (pooled OR 0.99; 95%CI 0.89 to 1.08; I2 = 0.0%, p = 0.571) were considered. A publication bias was detected. An association between shift work and prostate cancer cannot be confirmed with the available current data. Future analytical studies assessing more objective homogeneous exposure variables still seem necessary.

IARC 2019: "Night shift work" is probably carcinogenic: What about disturbed chronobiology in all walks of life?

In June of 2019, a working group convened by the International Agency for Research on Cancer [IARC] concluded that “night shift work” is probably carcinogenic to humans (a Group 2A carcinogen). This was based on sufficient evidence of cancer and strong mechanistic evidence in experimental animals and limited evidence from human epidemiological studies. The biological basis from experimental work is clear and compelling: Disturbed chronobiology such as due to alterations in the light-dark schedule which shift-workers experience is associated with carcinogenicity. But is it correct to assume in epidemiological studies that “night shift work” provides the same dose of disturbed chronobiology to all night workers and that disturbed chronobiology from activities outside of work does not count? Both chronobiological theory and supporting evidence suggest that much-needed future epidemiology should address these questions and should consider disturbed chronobiology in all walks of life.

Night-Shift Work and Risk of Prostate Cancer: Results From a Canadian Case-Control Study, the Prostate Cancer and Environment Study

Night-shift work involving disruption of circadian rhythms has been associated with breast cancer risk. A role in prostate cancer is also suspected, but evidence is limited. We investigated the association between night-shift work and prostate cancer incidence in the Prostate Cancer and Environment Study (PROtEuS), a population-based case-control study conducted in 2005-2012 in Montreal, Quebec, Canada. Participants were 1,904 prostate cancer cases (432 high-grade cancers) and 1,965 population controls. Detailed work schedules for each job held for at least 2 years (n = 15,724) were elicited in face-to-face interviews. Night-shift work was defined as having ever worked ≥3 hours between midnight and 5:00 am ≥3 nights/month for ≥1 year. Unconditional logistic regression was used to estimate odds ratios and 95% confidence intervals for the association between night-shift work and prostate cancer, adjusting for age, ancestry, and education. No association was found between overall prostate cancer and night-shift work metrics, including ever exposure, duration, intensity, cumulative exposure, rotating shifts, and early-morning shifts. For none of the exposure indices was there evidence of heterogeneity in odds ratios between low- and high-grade cancers. Sensitivity analyses restricting exposures to ≥7 nights/month or considering screening history yielded similar results. Our findings lend no support for a major role of night-shift work in prostate cancer development.

Night shiftwork and prostate-specific antigen level in a tire manufacturing factory

BACKGROUND

Recent studies suggest that night shiftwork may increase the risk of prostate cancer and elevated serum prostate-specific antigen (PSA) level. The purpose of this study was to verify whether rotating night shiftwork affects serum PSA level.

METHODS

This study included 3,195 male production workers who work in a large tire manufacturing factory. Serum PSA levels were measured and the data on related factors were obtained.

RESULTS

The mean serum PSA level was 0.98 ± 0.79 ng/mL. PSA levels were significantly lower in the younger age group, the obese group, and regular exercise group. PSA levels were lower in night shift workers (n = 2,832) compared to day workers (n = 363), but the difference was not statistically significant.

CONCLUSIONS

Unlike previous studies, we did not find any evidence that night shiftwork results in an increase in serum PSA levels. Further research and consistent results are needed to elucidate the association between night shiftwork and the effect on the prostate.

Interplay between Circadian Clock and Cancer: New Frontiers for Cancer Treatment

Circadian clocks constitute the evolutionary molecular machinery that dictates the temporal regulation of physiology to maintain homeostasis. Disruption of the circadian rhythm plays a key role in tumorigenesis and facilitates the establishment of cancer hallmarks. Conversely, oncogenic processes directly weaken circadian rhythms. Pharmacological modulation of core clock genes is a new approach in cancer therapy. The integration of circadian biology into cancer research offers new options for making cancer treatment more effective, encompassing the prevention, diagnosis, and treatment of this devastating disease. This review highlights the role of the circadian clock in tumorigenesis and cancer hallmarks, and discusses how pharmacological modulation of circadian clock genes can lead to new therapeutic options.