Nightshift work and risk of ovarian cancer
ABSTRACT OBJECTIVES: Animal evidence suggests that circadian disruption may be associated with ovarian cancer, though very little epidemiological work has been done to assess this potential association. We evaluated the association between self-reported nightshift work, a known circadian disruptor, and ovarian cancer in a population-based case-control study. METHODS: The study included 1101 women with invasive epithelial ovarian cancer, 389 women with borderline epithelial ovarian tumours and 1832 controls and was conducted in western Washington state. Shift work data were collected as part of inperson interviews. RESULTS: Working the nightshift was associated with an increased risk of invasive (OR=1.24, 95% CI 1.04 to 1.49) and borderline (OR=1.48, 95% CI 1.15 to 1.90) tumours; however, we observed little evidence that risks increased with increasing cumulative duration of nightshift work, and risks were not elevated in the highest duration category (>7 nightshift work-years). Increased risks were restricted to women who were 50 years of age and older and to serous and mucinous histologies of invasive and borderline tumours. There was suggestive evidence of a decreased risk of ovarian cancer among women reporting a preference for activity during evenings rather than mornings. CONCLUSIONS: We found evidence suggesting an association between shift work and ovarian cancer. This observation should be followed up in future studies incorporating detailed assessments of diurnal preference (ie, chronotype) in addition to detailed data on shift schedules.
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ABSTRACT: The aim of this study was to examine the relation between chronotype and breast cancer risk. We analyzed the association between chronotype (definite morning type, probable morning type, probable evening type, definite evening type, or neither morning nor evening type) and breast cancer risk among 72 517 women in the Nurses' Health Study II (NHS II). Chronotype was self-reported in 2009, and 1834 breast cancer cases were confirmed among participants between 1989 and 2007; a 2-yr lag period was imposed to account for possible circadian disruptions related to breast cancer diagnosis. Age- and multivariable-adjusted logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Participants who self-reported as neither morning nor evening type had a 27% increased risk of breast cancer (multivariable-adjusted OR = 1.27, 95% CI = 1.04-1.56), compared with definite morning types. None of the other chronotypes were significantly associated with breast cancer risk (multivariable-adjusted OR = 0.99, 95% CI = 0.87-1.12 for probable morning versus definite morning types; OR = 0.96, 95% CI = 0.84-1.09 for probable evening versus definite morning types; and OR = 1.15, 95% CI = 0.98-1.34 for definite evening versus definite morning types). Overall, chronotype was not associated with breast cancer risk in our study. A modestly increased risk among neither morning nor evening types may indicate circadian disruption as a potentially underlying mechanism; however, more studies are needed to confirm our results.Chronobiology International 08/2013; 30(9). DOI:10.3109/07420528.2013.809359 · 2.88 Impact Factor
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ABSTRACT: Abstract Objective: To characterize Ayurvedic perspectives on the etiopathogenesis and supportive treatments for a biomedical diagnosis of cancer. Methods: Hour-long, digitally recorded interviews were conducted with 10 experienced Ayurvedic clinicians, transcribed verbatim, and analyzed using techniques of qualitative thematic analysis. Results: Four major themes were identified. The Ayurvedic description of the pathophysiology of cancer uses traditional concepts translated into a modern context. Although the biomedical treatment of cancer is considered valuable, from an Ayurvedic perspective it results in degeneration and depletion. In cases where biomedical treatment of cancer is not feasible, an Ayurvedic approach focusing on strengthening digestion, eliminating toxins, reducing tumor growth, and improving tissue metabolism is useful. An Ayurvedic approach to cancer supportive care focuses on restoring equilibrium, building strength, and rejuvenation. Conclusion: Ayurvedic medicine offers a unique perspective on the biomedical diagnosis of cancer that emphasizes restoring wholeness, uses natural remedies, includes a focus on emotional health, and emphasizes prevention strategies.Journal of alternative and complementary medicine (New York, N.Y.) 12/2013; 20. DOI:10.1089/acm.2013.0259 · 1.52 Impact Factor
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ABSTRACT: Melatonin, a marker for the circadian rhythm with serum levels peaking between 2AM and 5AM, is hypothesized to possess anti-cancer properties, making it a mechanistic candidate for the probable carcinogenic effect of circadian rhythm disruption. In order to weigh epidemiologic evidence on the association of melatonin with cancer, we must first understand the laboratory and biological sources of variability in melatonin levels measured in samples. Participants for this methodological study were men enrolled in the Prostate Lung Colorectal and Ovarian Cancer Screening Trial (PLCO). We measured serum melatonin levels over a five year period in 97 individuals to test if melatonin levels are steady over time. The Pearson correlation coefficient between two measures separated by 1 year was 0.87, while the correlation between two measures separated by 5 years was to 0.70. In an additional cross-sectional study of 292 individuals, we used Analysis of Variance to identify differences in melatonin levels between different lifestyle and environmental characteristics. Serum melatonin levels were slightly higher in samples collected from 130 individuals during the winter, (6.36±0.59 pg/ml) than in samples collected from 119 individuals during the summer (4.83±0.62 pg/ml). Serum melatonin levels were lowest in current smokers (3.02±1.25 pg/ml, p = 0.007) compared to never (6.66±0.66 pg/ml) and former (5.59±0.50 pg/ml) smokers whereas BMI did not significantly affect serum melatonin levels in this study. In conclusion, the high 5 year correlation of melatonin levels implies that single measurements may be used to detect population level associations between melatonin and risk of cancer. Furthermore, our results reiterate the need to record season of sample collection, and individual characteristics in order to maximize study power and prevent confounding.PLoS ONE 12/2013; 8(12):e83208. DOI:10.1371/journal.pone.0083208 · 3.23 Impact Factor