Biological Rhythms Impact of 12 Hours Shift Work (MELACTI-12)

Wake-sleep Cycle and Melatonin Secretion Dynamics Associated With 12 Hours Shift Work in French Nurses

Nonstandard time-schedules work are widespread in the world of work. Shift and night work have been shown to be responsible for a desynchronization of biological rhythms, associated with melatonin secretion impairment and sleep disturbances. However, while health consequences of night and shift work are widely recognized and represent a major public health concern (High Authority of Health 2012 Recommendations and National Agency for Public Health Food, Environment and Work 2016 Report), the mechanisms by which the circadian system is affected by shift work remain poorly understood. Indeed most of the studies in the fields are cross-sectional, based on few blood or urinary samples in a single work position, in workers whose shift work patterns are often misidentified and heterogeneous. Moreover, few studies have assessed melatonin secretion alterations in relation to objective sleep measurement (actigraphy). The aim of this study is to assess the dynamics of melatonin secretion adaptation in 12-hour shift work and to correlate these data to sleep-wake cycle recording.

14 healthy volunteer nurses working on 12 hours night/day schedules in the Sleep Medicine Center of Lyon.

The study will take place over 15 days during which the nurses will wear an actigraphic wristband and will fulfill a sleep log. During 3 periods of 24 hours selected during these 15 days, including a 12h day shift (Day 2), a 12h night shift (Day 8) and a rest (Day 13), the participants will collect their urine by 4 to 8 hour periods, note the corresponding urine volumes and for each period, sample a 5 mL tube which will be analyzed later (6-sulfatoxymelatonin and urinary cortisol assays). The subjects will complete questionnaires at the beginning of the study (Horne and Ostberg, Insomnia Severity Index, Epworth, Pichot, Hospital Anxiety and Depression) and the days corresponding to the urine sampling (Karolinska and St Mary Hospital).

The impact of 12H shift work on melatonin secretion dynamics will be assessed by comparing the total amount of melatonin excreted during the sleep period between the 12h day shift condition and the 12h night shift condition

The impact of 12H shift work on melatonin secretion dynamics will be assessed by comparing the total amount of melatonin excreted during the sleep period between the 12h day shift condition and the 12h night shift condition

the total amount of melatonin excreted during the sleep period at rest will be compared to the total amount of melatonin excreted during the sleep period for the 12h day shift condition ant to the total amount of melatonin excreted during the sleep period for the 12h night shift condition

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of total excretion (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of acrophase (h)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of amplitude (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of mesor (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of total excretion (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of acrophase (h)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of amplitude (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of mesor (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of total excretion (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of acrophase (h)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of amplitude (ng)

Secretion of melatonin on sequential urinary specimens collected every 4 or 8 hours. Measure of mesor (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of total excretion (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of acrophase (h)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of amplitude (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of mesor (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of total excretion (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of acrophase (h)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of amplitude (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of mesor (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of total excretion (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of acrophase (h)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of amplitude (ng)

Secretion of cortisol on sequential urinary specimens collected every 4 or 8 hours. Measure of mesor (ng)

Inclusion Criteria: Nurses or nursing assistants working in the Sleep and Respiratory Diseases Department of the Croix-Rousse Hospital with positions in 12 hours for more than 6 months informed consent given by the subject Exclusion Criteria: Pregnancy or lactation <6 months Taking treatment modifying the secretion of melatonin (melatoninergic drugs (including antidepressants), beta-blockers) Refusal of participate Minor or major protected subject Not affiliated to a social security scheme Participant in another interventional study interfering with sleep / wake rhythm or work schedules (judgment of the investigator)