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Sleep duration is a novel and potentially modifiable risk factor for cancer. We evaluated the association of self-reported sleep duration and daytime napping with odds of colorectal and gastric cancer. We included 2008 incident colorectal cancer cases, 542 gastric cancer cases and 3622 frequency-matched population controls, recruited in the MCC-Spain case-control study (2008-2013). Sleep information, socio-demographic and lifestyle characteristics were obtained through personal interviews. Multivariable adjusted logistic regression models were used to estimate odds ratios (OR) with 95% confidence intervals (CI) for cancer, across categories of sleep duration (≤ 5, 6, 7, 8, ≥ 9 hours/day), daytime napping frequency (naps/week) and duration (minutes/nap). Compared to 7 hours of sleep, long sleep was associated with increased odds of colorectal (OR ≥9 hours : 1.59; 95%CI 1.30-1.94) and gastric cancer (OR ≥9 hours : 1.95; 1.37-2.76); short sleep was associated with increased odds of gastric cancer (OR ≤5 hours : 1.32; 0.93-1.88). Frequent and long daytime naps increased the odds of colorectal (OR 6-7 naps/week, ≥30 min : 1.32; 1.14-1.54) and gastric cancer (OR 6-7 naps/week, ≥30 min : 1.56; 1.21-2.02). Effects of short sleep and frequent long naps were stronger among participants with night shift-work history. Sleep and circadian disruption may jointly play a role in the etiology of colorectal and gastric cancer.

Background: We hypothesized that the risk of colorectal cancer in night-shift workers might be different according to insulin receptor substrate status., Methods: Among 77,470 eligible women having night work assessed in the Nurses' Health Study, we documented a total of 1,397 colorectal cancer cases, of which 304 or 308 had available data on IRS1 and IRS2 , respectively. We used duplication-method Cox proportional hazards regression analysis for competing risks to calculate HRs and 95% confidence intervals (CI) for each colorectal cancer subtype. We measured tumor IRS1 or IRS2 expression by immunohistochemistry (IHC)., Results: Compared with women who never worked night shifts, those working ≥15 years night shifts had a marginal trend of increased overall risk of colorectal cancer ( P trend = 0.06; multivariable HR = 1.20; 95% CI, 0.99-1.45). Longer duration of night-shift work was associated with a higher risk of IRS2 -positive tumors (multivariable HR = 2.69; 95% CI, 1.48-4.89; P trend = 0.001, ≥15 years night shifts vs. never) but not with IRS2 -negative tumors (multivariable HR = 0.90; 95% CI, 0.54-1.51; P trend = 0.72; P heterogeneity for IRS2 = 0.008). Similarly, the corresponding multivariable HRs were 1.81 for IRS1 -positive tumors (95% CI, 0.94-3.48; P trend = 0.06) and 1.13 for IRS1 -negative tumors (95% CI, 0.71-1.80; P trend = 0.56; P heterogeneity for IRS1 = 0.02)., Conclusions: Our molecular pathologic epidemiology data suggest a potential role of IRS in mediating carcinogenesis induced by night-shift work., Impact: Although these findings need validation, rotating night shift might increase colorectal cancer risk in women with abnormal insulin receptor pathways., (©2019 American Association for Cancer Research.)

Animal and human data have suggested that shift work involving circadian disruption may be carcinogenic for humans, but epidemiological evidence for colorectal cancer remains limited. We investigated the association of rotating night shift work and colorectal cancer risk in two prospective female cohorts, the Nurses' Health Study (NHS) and NHS2, with 24 years of follow-up. In total, 190,810 women (NHS = 77,439; NHS2 = 113,371) were included in this analysis, and 1,965 incident colorectal cancer cases (NHS = 1,527; NHS2 = 438) were reported during followup (NHS: 1988-2012, NHS2: 1989-2013). We used Cox proportional hazards models adjusted for a wide range of potential confounders. We did not observe an association between rotating night work duration and colorectal cancer risk in these cohorts (NHS: 1-14 years: Hazard Ratio (HR) 1.04, 95% CI: 0.94, 1.16; 15+ years: HR 1.15, 95% CI: 0.95, 1.39; P trend = 0.14 and NHS2: 1-14 years: HR 0.81, 95% CI: 0.66, 0.99; 15+ years: HR 0.96, 95% CI: 0.56, 1.64 and P trend = 0.88). In subsite analysis in NHS, rectal cancer risk increased after long-term (15+ years) rotating night shift work (proximal colon cancer: HR 1.00, 95% CI: 0.75, 1.34, P trend = 0.90; distal colon cancer: HR 1.27, 95% CI: 0.87, 1.85, P trend = 0.32; rectal cancer: HR 1.60, 95% CI: 1.09, 2.34, P trend = 0.02). We found no overall evidence of an association between rotating night shift work and colorectal cancer risk in these two large cohorts of nurses. Risk for rectal cancer significantly increased with shift work duration, suggesting that long-term circadian disruption may play a role in rectal cancer development., (© 2018 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of UICC.)

Purpose: This study aims to investigate the associations of rotating night shift work history and sleep duration with risk of colorectal adenoma., Methods: We evaluated 56,275 cancer-free participants of the Nurses' Health Study II, who had their first colonoscopy or sigmoidoscopy between 1991 and 2011; rotating night shift work and sleep duration were reported by mailed questionnaire. Multivariable-adjusted logistic regression was used to estimate relative risks (RR) of colorectal adenoma, with 95% confidence intervals (CI), across categories of rotating night shift work history (none, 1-4, 5-9, and ≥10 years) and sleep duration (≤5, 6, 7, 8, and ≥9 h/day)., Results: We found no association between duration of rotating night shift work and occurrence of colorectal adenoma (p-trend across shift work categories = 0.5). Women with the longest durations of rotating night shift work (≥10 years) had a similar risk of adenoma compared to women without a history of rotating night shift work (multivariable-adjusted RR = 0.96, 95% CI = 0.83-1.11). Similarly, there were no associations of shorter or longer sleep durations with adenoma risk (p-trend = 0.2 across sleep durations of ≤5 through 7 h/day and p-trend = 0.5 across sleep durations of 7 through ≥9 h/day). Results were similar when we examined associations according to adenoma location and subtype., Conclusions: Our results do not support an association between rotating night shift work or sleep duration and risk of colorectal adenoma in women.

Objectives Shift work that involves circadian disruption has been associated with a higher cancer risk. Most epidemiological studies to date have focused on breast cancer risk and evidence for other common tumors is limited. We evaluated the risk for colorectal cancer (CRC) in relation to shift work history in a population-based case-control study in Spain. Methods This analysis included 1626 incident CRC cases and 3378 randomly selected population controls of both sexes, enrolled in 11 regions of Spain. Sociodemographic and lifestyle information was assessed in face-to-face interviews. Shift work was assessed in detail throughout lifetime occupational history. We estimated the risk of colon and rectal cancer associated with rotating and permanent shift work (ever, cumulative duration, age of first exposure) using unconditional logistic regression analysis adjusting for potential confounders. Results Having ever performed rotating shift work (morning, evening and/or night) was associated with an increased risk for CRC [odds ratio (OR) 1.22, 95% confidence interval (95% CI) 1.04-1.43], as compared to day workers. Having ever worked permanent night shifts (≥3 nights/month) was not associated with CRC risk (OR 0.79, 95% CI 0.62-1.00). OR increased with increasing lifetime cumulative duration of rotating shift work (P-value for trend 0.005) and were highest among subjects in the top quartiles of exposure (3 rd quartile, 20-34 years, OR 1.38, 95%CI 1.06-1.81; 4 th quartile, ≥35 years, OR 1.36, 95% CI 1.02-1.79). Conclusions These data suggest that rotating shift work may increase the risk of CRC especially after long-term exposures.