Night Work And Prostate Cancer Risk: Preliminary Findings From The Proteus Case-Control Study In Montreal, Canada
Marie-Elise PARENT, Université du Québec, Canada
NADON L. 1
,
RICHARD H. 1
,
YU J. 1
1 Epidemiology and Biostatistics Unit, INRS-Institut Armand-Frappier, Université du Québec, Laval, Canada
Background: In 2007, IARC classified shift work involving circadian disruption as a probable human carcinogen. Human evidence, mostly based on breast cancer, was judged as limited. A handful of studies have suggested an association between night work and prostate cancer (PCa) risk.
Purpose: To assess the association between night work, as defined by an IARC Working Group in 2010, and PCa risk.
Methods: PROtEuS, a population-based case-control study, was conducted in Montréal, Canada. Subjects included 1,933 incident PCa cases aged ≤ 75, diagnosed across French hospitals in Greater Montreal in 2005-2009. Concurrently, 1,994 population controls were randomly selected from French-speaking men on the electoral list. In-person interviews elicited in-depth information on each job held over the lifetime, including work schedules. Unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CI) for the association between night work and PCa risk, taking into account several potential confounders.
Results: 23% of cases and 21% of controls had held a night job (3 hours of work between midnight and 5:00 am), for at least 1 year. The average cumulative duration of night work was 7.8 ± 8.2 years for cases and 8.7 ± 8.7 years for controls. Compared to men having never held a night job, those who did had an OR for PCa of 1.05 (95%CI 0.88-1.25). The OR for high grade (Gleason 7 [4+3]) PCa was 1.09 (95%CI 0.85-1.38). There was no evidence of a duration-response trend. Excluding men working rotating shifts from the unexposed category did not alter findings. Nor did exclusion of controls not recently screened for PCa.
Conclusions: These preliminary findings provide little support to the hypothesis that night work plays a role in PCa development. In-depth analyses are underway.
Funding: Canadian Cancer Society, Cancer Research Society and the Quebec Government