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All about biological clocks: from light, rhythms, and health

Grant number: 18/17071-1
Support type:Research Grants - Visiting Researcher Grant - International
Duration: November 04, 2018 - November 09, 2018
Field of knowledge:Health Sciences - Collective Health
Principal Investigator:Elaine Cristina Marqueze
Grantee:Elaine Cristina Marqueze
Visiting researcher: Celine Vetter
Visiting researcher institution: University of Colorado Boulder, United States
Home Institution: Centro de Ciências Sociais Aplicadas. Universidade Católica de Santos (UNISANTOS). Santos , SP, Brazil


The present study aims to evaluate the effects of melatonin on the anthropometric variables, on sleep, hormonal, physiological and biochemical aspects of overweight and obese workers who work in fixed night shifts of 12x36 hours. A randomized double-blind clinical lTria crossover with nursing professionals will be performed, working only in fixed night shifts, in the 12x36 hour system (12 hours of night work and 36 hours of rest) in the city of São Paulo / SP. Among those able to participate in the study and willing to participate voluntarily, a randomization stratified by body mass index (1st stratum with BMI of 25 to 29.9kg/m2, 2nd stratum with BMI e 30 to 40kg/m2) will be performed. Within each stratum, participants from the intervention group and control group of the first stage of the study, with a duration of three months, will be randomized. Subsequently, the second stage of the study (three months duration) will be carried out, in which the first intervention stage will be control in the second stage, and vice versa. The stratum will be matched by the age group and current job function in the hospital. The intervention consists in the use of melatonin (3 mg dose) only on nurses' days off, that is, on days when they sleep at night. On night work days, melatonin will not be administered by the participants. The control group will be instructed to use a tablet identical to melatonin, but this will be placebo, receiving the same guidelines of use of the intervention group. Because it is a double blind study, neither the participants nor the responsible researcher will know when they will be part of the intervention group or the control group. As a reference for the calculation of the sample the performance of the test of comparison of two means (related samples), a significance level of 5% (± err prob = 0.05), effectiveness of 0.3 in the metabolic and sleep aspects evaluated and the minimum size for a sample strength of 80%, the calculated sample was 70 people. Considering a loss of 12%, the sample will consist of 80 people, 20 in each group (sample strength of 85%). The test of comparison of two means (related samples) of the metabolic and sleep variables, before and after intervention and also to test the difference of means between the control groups and the intervention groups will be used. And the proportions test to compare the two groups. In all tests, a "p" value of less than 0.05 will be considered significant. Statistica 12.0 and STATA 12.0 (Stata corp, Texas, USA) will be used for the statistical analysis. (AU)