Association between shift work and risk of prostate cancer: a systematic review and meta-analysis of observational studies

Abstract

Observational studies suggest that shift work may be associated with prostate cancer. However, the results are inconsistent. The objective of this study is to quantitatively assess the association between shift work and the risk of prostate cancer. Relevant studies were identified by a comprehensive search of the PubMed, Embase, Web of Science and China National Knowledge Infrastructure databases to September 2017. We also reviewed the reference lists from retrieved articles. Observational studies that reported relative risk (RR) with 95% confidence intervals (CIs) for the association between shift work and the risk of prostate cancer were included. Linear and non-linear dose-response meta-analyses were performed. Fifteen studies with 16 independent reports involving 2 546 822 individuals and 10 715 patients with prostate cancer were included. The pooled adjusted RR for the association between ever exposure to shift work and prostate cancer risk was 1.23 (95% CI, 1.08-1.41; P < 0.001). A non-linear association of prostate cancer risk with duration of shift work was identified (P for non-linearity = 0.001). Subgroup analysis demonstrated a higher pooled RR of prostate cancer for studies among Asian populations (RR = 1.98, 95% CI, 1.34-2.93; P = 0.618). A positive association was observed in rotating shift groups (RR = 1.10, 95% CI, 1.00-1.26; P = 0.156), but not in other shift groups. Integrated evidence from this meta-analysis suggests that shift work is significantly associated with an increased risk of prostate cancer, and a non-linear association between duration of shift work and prostate cancer was found.

Cancer risk among career male and female Florida firefighters: Evidence from the Florida Firefighter Cancer Registry (1981‐2014)

“…PAH, PCB, and heavy metal exposures have also been associated with prostate cancer risk 43 . In addition, pooled analyses of shiftwork and prostate cancer risk show an excess risk similar to that seen in pooled analyses of firefighters (Pooled relative risk = 1.23; 1.08‐1.41 vs SIRE = 1.15; 1.05‐1.27) 6,44 . Finally excess prostate cancer risk in firefighters could be an indication of detection bias due to greater screening access although the pattern of early vs late‐stage risk is opposite of what would be expected if such a bias was present (early: 1.13; 1.03‐1.23 vs late: 1.42; 1.19‐1.68).…”

Does the association of prostate cancer with night-shift work differ according to rotating vs. fixed schedule? A systematic review and meta-analysis

“…The most recent meta-analyses [7][8][9] examining the association between night-shift work and prostate cancer yielded an increased risk of prostate cancer among nightshift workers, with summary relative risk (RR) estimates ranging between 1.08 and 1.24. These apparently conflicting findings could result from heterogeneity between studies, which may be explained not only by differences in the study design and characteristics of the participants, but also by different night-shift work definitions and schedules, such as fixed vs. rotating.…”

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

“…However, summary measurements must be considered with caution, due to the high heterogeneity found, the high proportion of studies with low-medium methodological quality, and the possibility of publication bias. As we have previously mentioned, other authors have also tried to summarize available evidence [27][28][29][30][31][32][33], as shown in online Supplementary Table S1.…”

“…This explains the lower number of studies they included. Gan et al [28] also included a lower number of studies and did not observe publication bias. This last systematic review found an increased risk in prostate cancer in personnel working rotating shifts.…”

“…From an epidemiological perspective, a number of observational studies have tried to evaluate the association between shift work and prostate cancer, although their results do not always point in the same direction [25,26]. This has led to the conduction of several reviews and meta-analyses on this topic, albeit again with inconsistent results [27][28][29][30][31][32][33]. A detailed analysis reveals that they have significant methodological weaknesses, such as high unexplained heterogeneity [28], partial inclusion of the evidence due to restrictions based on study design [27] or type of exposure (i.e., restricted to permanent night jobs), or the absence of consideration of potential publication bias [32].…”