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Ashkenazi, I. E.; Reinberg, A,; Bicakova-Rocher, A.; Ticher, A. |
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The genetic background of individual variations of circadian-rhythm periods in healthy human adults. |
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Journal Article |
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1993 |
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American Journal of Human Genetics |
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52 |
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6 |
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1250–1259 |
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Human Health; Adult; Body Temperature; Bronchi; Bronchi: physiology; Circadian Rhythm; Circadian Rhythm: genetics; Female; Genetic Variation; Hand; Hand: physiology; Heart Rate; Humans; Male; Middle Aged; Sex Factors; Sleep |
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As a group phenomenon, human variables exhibit a rhythm with a period (tau) equal to 24 h. However, healthy human adults may differ from one another with regard to the persistence of the 24-h periods of a set of variables' rhythms within a given individual. Such an internal desynchronization (or individual circadian dyschronism) was documented during isolation experiments without time cues, both in the present study involving 78 male shift workers and in 20 males and 19 females living in a natural setting. Circadian rhythms of sleep-wake cycles, oral temperature, grip strength of both hands, and heart rate were recorded, and power-spectra analyses of individual time series of about 15 days were used to quantify the rhythm period of each variable. The period of the sleep-wake cycle seldom differed from 24 h, while rhythm periods of the other variables exhibited a trimodal distribution (tau = 24 h, tau > 24 h, tau < 24 h). Among the temperature rhythm periods which were either < 24 h or > 24 h, none was detected between 23.2 and 24 h or between 24 and 24.8 h. Furthermore, the deviations from the 24-h period were predominantly grouped in multiples of +/- 0.8 h. Similar results were obtained when the rhythm periods of hand grip strength were analyzed (for each hand separately). In addition, the distribution of grip strength rhythm periods of the left hand exhibited a gender-related difference. These results suggested the presence of genetically controlled variability. Consequently, the distribution pattern of the periods was analyzed to elucidate its compatibility with a genetic control consisting of either a two-allele system, a multiple-allele system, or a polygenic system. The analysis resulted in structuring a model which integrates the function of a constitutive (essential) gene which produces the exact 24-h period (the Dian domain) with a set of (inducible) polygenes, the alleles of which, contribute identical time entities to the period. The time entities which affected the rhythm periods of the variables examined were in the magnitude of +/- 0.8 h. Such an assembly of genes may create periods ranging from 20 to 28 h (the Circadian domain). The model was termed by us “The Dian-Circadian Model.” This model can also be used to explain the beat phenomena in biological rhythms, the presence of 7-d and 30-d periods, and interindividual differences in sensitivity of rhythm characteristics (phase shifts, synchronization, etc.) to external (and environmental) factors. |
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LoNNe @ schroer @ |
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582 |
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Parent, M.-E.; El-Zein, M.; Rousseau, M.-C.; Pintos, J.; Siemiatycki, J. |
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Title |
Night work and the risk of cancer among men |
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Journal Article |
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2012 |
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American Journal of Epidemiology |
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Am J Epidemiol |
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176 |
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9 |
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751-759 |
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Adult; Aged; *Circadian Rhythm; Humans; Male; *Men's Health; Middle Aged; Neoplasms/*epidemiology; Occupations/*statistics & numerical data; Personnel Staffing and Scheduling/*statistics & numerical data; Quebec/epidemiology; Risk Factors; oncogenesis |
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Night work might influence cancer risk, possibly via suppression of melatonin release. In a population-based case-control study conducted in Montreal, Quebec, Canada, between 1979 and 1985, job histories, including work hours, were elicited from 3,137 males with incident cancer at one of 11 anatomic sites and from 512 controls. Compared with men who never worked at night, the adjusted odds ratios among men who ever worked at night were 1.76 (95% confidence interval (CI): 1.25, 2.47) for lung cancer, 2.03 (95% CI: 1.43, 2.89) for colon cancer, 1.74 (95% CI: 1.22, 2.49) for bladder cancer, 2.77 (95% CI: 1.96, 3.92) for prostate cancer, 2.09 (95% CI: 1.40, 3.14) for rectal cancer, 2.27 (95% CI: 1.24, 4.15) for pancreatic cancer, and 2.31 (95% CI: 1.48, 3.61) for non-Hodgkin's lymphoma. Equivocal evidence or no evidence was observed for cancers of the stomach (odds ratio (OR) = 1.34, 95% CI: 0.85, 2.10), kidney (OR = 1.42, 95% CI: 0.86, 2.35), and esophagus (OR = 1.51, 95% CI: 0.80, 2.84) and for melanoma (OR = 1.04, 95% CI: 0.49, 2.22). There was no evidence of increasing risk with increasing duration of night work, with risks generally being increased across all duration categories. Results suggest that night work may increase cancer risk at several sites among men. |
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INRS-Institut Armand-Frappier, University of Quebec, Laval, Canada. marie-elise.parent@iaf.inrs.ca |
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0002-9262 |
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PMID:23035019 |
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IDA @ john @ |
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158 |
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Bhatti, P.; Mirick, D.K.; Davis, S. |
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Invited commentary: Shift work and cancer |
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2012 |
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American Journal of Epidemiology |
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Am J Epidemiol |
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176 |
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9 |
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760-3; discussion 764-5 |
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Human Health; Circadian Rhythm; Humans; Male; *Men's Health; Neoplasms/*epidemiology; Occupations/*statistics & numerical data; Personnel Staffing and Scheduling/*statistics & numerical data |
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In this issue of the Journal, Parent et al. (Am J Epidemiol. 2012;176(9):751-759) report significant associations between night-shift work and risk of cancer at several sites among men. These findings not only address the need for shift-work studies that evaluate cancers other than breast and prostate cancer but also support the increasing concern that the negative effects of shift work may be broadly applicable to risk of many cancers via the direct oncostatic properties of melatonin. Studies of shift work have been limited by a lack of detailed data for determining which aspects of this multifaceted exposure may be associated with increased cancer risk. Additionally, the influence of individual-level characteristics, such as preference for daytime activity versus nighttime activity or chronotype, has not been considered. In moving forward, launching new cohort studies of shift work and cancer risk is the most tenable approach, though it will be limited by the years of follow-up required in order to accrue adequate numbers of cancer cases. Studies incorporating biomarkers of effect are useful for providing immediate information that can aid not only in identifying the underlying mechanisms of the shift-work-cancer association but also in interpreting existing epidemiologic data and informing the design of future epidemiologic studies of cancer risk. |
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Program in Epidemiology, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA. pbhatti@fhcrc.org |
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0002-9262 |
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PMID:23035018 |
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LoNNe @ christopher.kyba @ |
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507 |
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Wright, K.P.J.; Hull, J.T.; Czeisler, C.A. |
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Relationship between alertness, performance, and body temperature in humans |
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2002 |
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American Journal of Physiology. Regulatory, Integrative and Comparative Physiology |
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Am J Physiol Regul Integr Comp Physiol |
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283 |
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6 |
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R1370-7 |
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Human Health; Adult; Attention/*physiology; *Body Temperature; Circadian Rhythm/physiology; Cognition/*physiology; Female; Humans; Male; Memory/physiology; Reaction Time; Sleep/physiology; Time Factors; Wakefulness/physiology; NASA Discipline Regulatory Physiology; Non-NASA Center |
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Body temperature has been reported to influence human performance. Performance is reported to be better when body temperature is high/near its circadian peak and worse when body temperature is low/near its circadian minimum. We assessed whether this relationship between performance and body temperature reflects the regulation of both the internal biological timekeeping system and/or the influence of body temperature on performance independent of circadian phase. Fourteen subjects participated in a forced desynchrony protocol allowing assessment of the relationship between body temperature and performance while controlling for circadian phase and hours awake. Most neurobehavioral measures varied as a function of internal biological time and duration of wakefulness. A number of performance measures were better when body temperature was elevated, including working memory, subjective alertness, visual attention, and the slowest 10% of reaction times. These findings demonstrate that an increased body temperature, associated with and independent of internal biological time, is correlated with improved performance and alertness. These results support the hypothesis that body temperature modulates neurobehavioral function in humans. |
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Division of Sleep Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. kenneth.wright@colorado.edu |
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0363-6119 |
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PMID:12388468 |
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LoNNe @ kagoburian @ |
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Wood, B.; Rea, M.S.; Plitnick, B.; Figueiro, M.G. |
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Light level and duration of exposure determine the impact of self-luminous tablets on melatonin suppression |
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2013 |
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Applied Ergonomics |
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Appl Ergon |
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44 |
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2 |
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237-240 |
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Adolescent; *Computers, Handheld; Female; Humans; Light/*adverse effects; Male; Melatonin/*biosynthesis; Photoperiod; Saliva/*metabolism; Sleep/radiation effects; Time Factors; Young Adult; melatonin |
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Exposure to light from self-luminous displays may be linked to increased risk for sleep disorders because these devices emit optical radiation at short wavelengths, close to the peak sensitivity of melatonin suppression. Thirteen participants experienced three experimental conditions in a within-subjects design to investigate the impact of self-luminous tablet displays on nocturnal melatonin suppression: 1) tablets-only set to the highest brightness, 2) tablets viewed through clear-lens goggles equipped with blue light-emitting diodes that provided 40 lux of 470-nm light at the cornea, and 3) tablets viewed through orange-tinted glasses (dark control; optical radiation <525 nm approximately 0). Melatonin suppressions after 1-h and 2-h exposures to tablets viewed with the blue light were significantly greater than zero. Suppression levels after 1-h exposure to the tablets-only were not statistically different than zero; however, this difference reached significance after 2 h. Based on these results, display manufacturers can determine how their products will affect melatonin levels and use model predictions to tune the spectral power distribution of self-luminous devices to increase or to decrease stimulation to the circadian system. |
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Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180, USA. woodb5@rpi.edu |
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0003-6870 |
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IDA @ john @ |
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