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Experimental evidence indicates that exercise performed at different times of the day may affect circadian rhythms and circadian disruption has been linked to breast and prostate cancer. We examined in a population-based case-control study (MCC-Spain) if the time-of-day when physical activity is done affects prostate and breast cancer risk. Lifetime recreational and household physical activity was assessed by in-person interviews. Information on time-of-day of activity (assessed approximately 3 years after the assessment of lifetime physical activity and confounders) was available for 781 breast cancer cases, 865 population female controls, 504 prostate cases and 645 population male controls from 10 Spanish regions, 2008-2013. We estimated odds ratios (ORs) and 95% confidence intervals (95% CI) for different activity timings compared to inactive subjects using unconditional logistic regression adjusting for confounders. Early morning (8-10 am) activity was associated with a protective effect compared to no physical activity for both breast (OR = 0.74, 95% CI = 0.48-1.15) and prostate cancer (OR = 0.73, 95% CI = 0.44-1.20); meta-OR for the two cancers combined 0.74 (95%CI = 0.53-1.02). There was no effect observed for breast or prostate cancer for late morning to afternoon activity while a protective effect was also observed for evening activity only for prostate cancer (OR = 0.75, 95% CI = 0.45-1.24). Protective effects of early morning activity were more pronounced for intermediate/evening chronotypes for both cancers. This is the first population-based investigation identifying a differential effect of timing of physical activity on cancer risk with more pronounced effects for morning hour activity. Our results, if confirmed, may improve current physical activity recommendations for cancer prevention., (© 2020 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of Union for International Cancer Control.)

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.)

Modern life involves mistimed sleeping and eating patterns that in experimental studies are associated with adverse health effects. We assessed whether timing of meals is associated with breast and prostate cancer risk taking into account lifestyle and chronotype, a characteristic correlating with preference for morning or evening activity. We conducted a population-based case-control study in Spain, 2008-2013. In this analysis we included 621 cases of prostate and 1,205 of breast cancer and 872 male and 1,321 female population controls who had never worked night shift. Subjects were interviewed on timing of meals, sleep and chronotype and completed a Food Frequency Questionaire. Adherence to the World Cancer Research Fund/American Institute of Cancer Research recommendations for cancer prevention was examined. Compared with subjects sleeping immediately after supper, those sleeping two or more hours after supper had a 20% reduction in cancer risk for breast and prostate cancer combined (adjusted Odds Ratio [OR] = 0.80, 95%CI 0.67-0.96) and in each cancer individually (prostate cancer OR = 0.74, 0.55-0.99; breast cancer OR = 0.84, 0.67-1.06). A similar protection was observed in subjects having supper before 9 pm compared with supper after 10 pm. The effect of longer supper-sleep interval was more pronounced among subjects adhering to cancer prevention recommendations (OR both cancers= 0.65, 0.44-0.97) and in morning types (OR both cancers = 0.66, 0.49-0.90). Adherence to diurnal eating patterns and specifically a long interval between last meal and sleep are associated with a lower cancer risk, stressing the importance of evaluating timing in studies on diet and cancer., (© 2018 The Authors. International Journal of Cancer published by John Wiley & Sons Ltd on behalf of Union for International Cancer Control.)

Chronic lymphocytic leukemia (CLL) has few known modifiable risk factors. Recently, circadian disruption has been proposed as a potential contributor to lymphoid neoplasms' etiology. Serum melatonin levels have been found to be significantly lower in CLL subjects compared with healthy controls, and also, CLL prognosis has been related to alterations in the circadian molecular signaling. We performed the first investigation of an association between night shift work and CLL in 321 incident CLL cases and 1728 population-based controls in five areas of Spain. Participants were interviewed face-to-face by trained interviewers to collect information on sociodemographic factors, familial, medical and occupational history, including work shifts and other lifestyle factors. We used logistic regression models adjusted for potential confounders to estimate odds ratios (OR) and 95% confidence intervals (CI). Seventy-nine cases (25%) and 339 controls (20%) had performed night work. Overall, working in night shifts was not associated with CLL (OR = 1.06; 95% CI = 0.78-1.45, compared with day work). However, long-term night shift (>20 years) was positively associated with CLL (OR(tertile 3 vs . day-work)  = 1.77; 95% = 1.14-2.74), although no linear trend was observed (P trend = 0.18). This association was observed among those with rotating (OR(tertile 3 vs . day-work)  = 2.29; 95% CI = 1.33-3.92; P trend = 0.07), but not permanent night shifts (OR(tertile 3 vs . day-work) = 1.16; 95% CI = 0.60-2.25; P trend = 0.86). The association between CLL and long-term rotating night shift warrants further investigation., (© 2016 UICC.)

Night shift work has been classified as a probable human carcinogen based on experimental studies and limited human evidence on breast cancer. Evidence on other common cancers, such as prostate cancer, is scarce. Chronotype is an individual characteristic that may relate to night work adaptation. We evaluated night shift work with relation to prostate cancer, taking into account chronotype and disease severity in a population based case-control study in Spain. We included 1,095 prostate cancer cases and 1,388 randomly selected population controls. We collected detailed information on shift schedules (permanent vs. rotating, time schedules, duration, frequency), using lifetime occupational history. Sociodemographic and lifestyle factors were assessed by face-to-face interviews and chronotype through a validated questionnaire. We used unconditional logistic regression analysis adjusting for potential confounders. Subjects who had worked at least for one year in night shift work had a slightly higher prostate cancer risk [Odds Ratio (OR) 1.14; 95%CI 0.94, 1.37] compared with never night workers; this risk increased with longer duration of exposure (≥ 28 years: OR 1.37; 95%CI 1.05, 1.81; p-trend = 0.047). Risks were more pronounced for high risk tumors [D'Amico classification, Relative Risk Ratio (RRR) 1.40; 95%CI 1.05, 1.86], particularly among subjects with longer duration of exposure (≥28 years: RRR 1.63; 95%CI 1.08, 2.45; p-trend = 0.027). Overall risk was higher among subjects with an evening chronotype, but also increased in morning chronotypes after long-term night work. In this large population based study, we found an association between night shift work and prostate cancer particularly for tumors with worse prognosis., (© 2014 UICC.)