Chronotype and Breast Cancer Risk in a Cohort of US Nurses

Ramin, Cody; Devore, Elizabeth E.; Pierre-Paul, Jeffrey; Duffy, Jeanne F.; Hankinson, Susan E.; Schernhammer, Eva

doi:10.3109/07420528.2013.809359

Cited by 45 publications

(33 citation statements)

References 33 publications

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“…The observed differences we found in chronotype among shift workers (ie, a lower proportion of morning chronotypes among night shift workers) were consistent with previous publications 8 36 37. Recent studies36 37 have provided evidence that evening or ‘neither’ (ie, neither morning nor evening) chronotype may be associated with an increased risk of breast cancer compared to morning chronotype.…”

Section: Discussionsupporting

confidence: 91%

“…Recent studies36 37 have provided evidence that evening or ‘neither’ (ie, neither morning nor evening) chronotype may be associated with an increased risk of breast cancer compared to morning chronotype. While further research is warranted to validate these findings, it is nevertheless interesting that we observed a lower prevalence of morning types and less favourable health characteristics among night shift workers.…”

Section: Discussionmentioning

confidence: 99%

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Night shift work at specific age ranges and chronic disease risk factors

et al. 2014

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Objectives We examined the association of night shift work history and age when night shift work was performed with cancer and cardiovascular disease risk factors among 54 724 women in the Nurses' Health Study (NHS) II. Methods We calculated age-adjusted and socioeconomic status-adjusted means and percentages for cancer and cardiovascular risk factors in 2009 across categories of night shift work history. We used multivariable-adjusted logistic regression to estimate odds ratios (ORs) and 95% CIs for key risk factors among 54 724 participants (72% ever shift workers). We further examined these associations by age (20–25, 26–35, 36– 45 and 46+ years) at which shift work was performed. Results Ever night shift workers had increased odds of obesity (body mass index ≥30 kg/m2; OR=1.37, 95% CI 1.31 to 1.43); higher caffeine intake (≥131 mg/day; OR=1.16, 95% CI 1.12 to 1.22) and total calorie intake (≥1715 kcal/day; OR=1.09, 95% CI 1.04 to 1.13); current smoking (OR=1.30, 95% CI 1.19 to 1.42); and shorter sleep durations (≤7 h of sleep/day; OR=1.19, 95% CI 1.15 to 1.24) compared to never night shift workers. These estimates varied depending on age at which night work was performed, with a suggestion that night shift work before age 25 was associated with fewer risk factors compared to night shift work at older ages. Conclusions Our results indicate that night shift work may contribute to an adverse chronic disease risk profile, and that risk factors may vary depending on the age at which night shift work was performed.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Night shift work at specific age ranges and chronic disease risk factors

et al. 2014

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“…These results provide a different perspective to the hypothesis of eveningness as a facilitating individual characteristic in shift workers. The present results also add to several recent findings identifying the importance of chronotype as a mediating factor of health in shift workers (Asaoka et al, 2013;Ramin et al, 2013). Therefore, this study emphasizes the need for further investigation regarding how chronotype is related to circadian adaptation, general health and functioning in shift work schedules.…”

Section: Discussionsupporting

confidence: 74%

Day and night shift schedules are associated with lower sleep quality in Evening-types

Martin

Laberge

Sasseville

et al. 2015

Chronobiology International

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Eveningness has been suggested as a facilitating factor in adaptation to shift work, with several studies reporting evening chronotypes (E-types) as better sleepers when on night shifts. Conversely, eveningness has been associated with more sleep complaints during day shifts. However, sleep during day shifts has received limited attention in previous studies assessing chronotypes in shift workers. Environmental light exposure has also been reported to differ between chronotypes in day workers. Activity is also known to provide temporal input to the circadian clock. Therefore, the aim of this study was to compare objective sleep, light exposure and activity levels between chronotypes, both during the night and day shifts. Thirty-nine patrol police patrol officers working on a fast rotating shift schedule (mean age ± SD: 28.9 ± 3.2 yrs; 28 males) participated in this study. All subjects completed the Morningness-Eveningness Questionnaire (MEQ). Sleep and activity were monitored with actigraphy (Actiwatch-L; Mini-Mitter/Respironics, Bend, OR) for four consecutive night shifts and four consecutive day shifts (night work schedule: 00:00 h-07:00 h; day work schedule: 07:00 h-15:00 h). Sleep and activity parameters were calculated with Actiware software. MEQ scores ranged from 26 to 56; no subject was categorized as Morning-type. E-types (n = 13) showed significantly lower sleep efficiency, longer snooze time and spent more time awake after sleep onset than Intermediate-types (I-types, n = 26) for both the night and day shifts. E-types also exhibited shorter and more numerous sleep bouts. Furthermore, when napping was taken into account, E-types had shorter total sleep duration than I-types during the day shifts. E-types were more active during the first hours of their night shift when compared to I-types. Also, all participants spent more time active and had higher amount of activity per minute during day shifts when compared to night shifts. No difference was found regarding light exposure between chronotypes. In conclusion, sleep parameters revealed poorer sleep quality in E-types for both the night and day shifts. These differences could not be explained by sleep opportunity, light exposure or activity levels. This study challenges the notion that E-types adapt better to night shifts. Further studies must verify whether E-types exhibit lower sleep quality than Morning-types.

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“…Very little is known about the association between chronotype and cancer risk (43). Chronotype has been suggested as a possible effect modifier for the night shift work-cancer association (43,44). Our findings provide evidence that subjects with morning preference might be a group more susceptible to light-at-night effects and night shift work-related circadian disruption.…”

Section: <0001supporting

confidence: 55%

“…We did not find an association between diurnal preference and aMT6s acrophase in night shift workers, as we had expected, perhaps because we lacked subjects with extreme morning or evening preferences, or due to low numbers. Very little is known about the association between chronotype and cancer risk (43). Chronotype has been suggested as a possible effect modifier for the night shift work-cancer association (43,44).…”

Section: <0001mentioning

confidence: 99%

Circadian Variation of Melatonin, Light Exposure, and Diurnal Preference in Day and Night Shift Workers of Both Sexes

Papantoniou

Pozo

Espinosa

et al. 2014

Cancer Epidemiology, Biomarkers &Amp; Prevention

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Background: Light-at-night has been shown in experimental studies to disrupt melatonin production but this has only partly been confirmed in studies of night shift workers. In this cross-sectional study, we examined the circadian variation of melatonin in relation to shift status, individual levels of light-at-night exposure, and diurnal preference, an attribute reflecting personal preference for activity in the morning or evening.Methods: One hundred and seventeen workers (75 night and 42 day) of both sexes, ages 22 to 64 years, were recruited from four companies. Participants collected urine samples from all voids over 24 hours and wore a data logger continuously recording their light exposure. Sociodemographic, occupational, lifestyle, and diurnal preference information were collected by interview. Concentrations of urinary 6-sulfatoxymelatonin (aMT6s), the main melatonin metabolite, were measured.Results: Mean aMT6s levels were lower in night [10.9 ng/mg creatinine/hour; 95% confidence interval (CI), 9.5-12.6] compared with day workers (15.4; 95% CI, 12.3-19.3). The lowest aMT6s levels were observed in night workers with morning preference (6.4; 95% CI, 3.0-13.6). Peak time of aMT6s production occurred 3 hours later in night (08:42 hour, 95% CI, 07:48-09:42) compared with day workers (05:36 hour, 95% CI, 05:06-06:12). Phase delay was stronger among subjects with higher light-at-night exposure and number of nights worked.Conclusions: Night shift workers had lower levels and a delay in peak time of aMT6s production over a 24-hour period. Differences were modified by diurnal preference and intensity of light-at-night exposure.Impact: Night shift work affects levels and timing of melatonin production and both parameters may relate to future cancer risk. Cancer Epidemiol Biomarkers Prev; 23(7); 1176-86. Ó2014 AACR.

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Chronotype and Breast Cancer Risk in a Cohort of US Nurses

Cited by 45 publications

References 33 publications

Night shift work at specific age ranges and chronic disease risk factors

Night shift work at specific age ranges and chronic disease risk factors

Day and night shift schedules are associated with lower sleep quality in Evening-types

Circadian Variation of Melatonin, Light Exposure, and Diurnal Preference in Day and Night Shift Workers of Both Sexes

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