Shift work deeply impacts on temporal organization leading to a circadian desynchronization, which translates into a worsening of the sleep quality and work ability during waking hours. Furthermore, also the fine motor control skills and the subjective mood profile could undergo modifications in relation to the acquired sleep debt. The misalignment between working time and physiological/behavioral functions could have negative influences on the levels of spontaneous daily activity, with possible alteration of the activity-rest rhythm of the worker, especially in clinics.

In relation to the participants' chronotype, the aim of this project will be to evaluate the effect of irregular working hours (shift work) on (i) the sleep quality, (ii) the circadian rhythm of activity levels and, (iii) the motor control. These assessments will help to identify the shift type with less impact on the health status in a nurse cohort.

Shift work can exert numerous effects on the temporal and behavioral organization of the individuals. Working hours of shift workers, which are outside the normal daily social program, lead to a circadian desynchronization due to a temporary misalignment between working time and physiological and behavioral functions, similarly to what is observed in the jet lag syndrome. This may lead to deterioration in the sleep quality, reduction in the working ability during waking hours, with sleepiness and a reduction in the vigilance state.

Over the years, the impact of shift work has involved many areas and its effects have been investigated at the cardiovascular (coronary artery disease, hypertension), metabolic (diabetes and obesity) and immunological level. Several investigations provided evidence of the shift work-induced negative results on health, including carcinogenic effects. Consequently, the scientific community paid to these problems great attention.

In analyzing the health effects of shift work, the chronotype of the workers, or their circadian typology, is very important. In fact, the circadian rhythms represent a dimension of the human personality that should not be underestimated. The human being has a temporal organization, determined by the interaction of endogenous and environmental factors, and organizes most of the biological and behavioral activities according to a twenty-four hour period and in sync with the light-dark cycle. It is not worthy to mention that the biological rhythms in humans present interindividual differences that determine precisely the chronotype, which is the tendency to express preferences toward morning or evening activities. Within the population, it is possible to recognize subjects that can be traced to three circadian types: (i) morning-types subjects (M-Types) that tend to be more active and efficient in the first part of the day, (ii) evening-types subjects (E-Types) who find it difficult to get up in the morning and require more time to reach the optimal level of physical and mental efficiency, and (iii) intermediate subjects (Neither-Types, N-Types) that present intermediate characteristics between the previous two.

Previous studies suggested that the eveningness could determine an easier adaptability to the changes determined by shift work. However, the role of the chronotype on this aspect is yet to be related to the type of shift: on one side, the E-Types tend to have more sleep disorders induced by a diurnal working shift. On the other side, the M-Types tend to adapt worst to a night working shift. In any case, shift work determines a growing sleep debt that can have a not negligible impact on the wellbeing and health of the individual.

The association between shift work and cardiovascular risk is very interesting. Sleep at night, in fact, can have important effects on blood pressure. Some studies have shown that a good sleep quality may have potential effects in the prevention of hypertension. Arterial pressure decreases by an average of 10-20% during nighttime hours, so sleep debt could lead to higher average blood pressure over the course of twenty-four hours. In addition, by modifying the circadian rhythms, the shift may lead to an alteration of the autonomic nervous system regulation with hypertensive consequences.

This project will focus on a particular category of shift workers, i.e., the nurse staff working in a hospital. Nurse staff has three different shift schedules: (i) shift changes every day (the first day from 7.00 to 14.00, the second day from 14.00 to 21.00, the third day from 21.00 to 7.00, the fourth day night off and, the fifth day rest), with a "shift cycle" duration of 5 days; (ii) shift changes every two days (first and second day from 7.00 to 14.00, third and fourth day from 14.00 to 21.00, fifth day rest, sixth and seventh day from 21.00 to 7.00, eighth day night off and ninth and tenth day rest), with a shift cycle of 10 days; and (iii) only diurnal shifts (first day from 7.00 to 14.00 and the second day from 14.00 to 21.00), with 2 days of rest every 5 work days.

To this purpose, the aim of this project will be to identify the type of shift work schedule with less impact on the state of health of the hospital staff by evaluating the effect of different shift work schedules on the quality of sleep, on the circadian rhythm of activity levels and on motor control, in relation to the participants' chronotype.

Inclusion Criteria:

• Work shift continuity in a specific group of at least one year.

Exclusion Criteria:

• Presence of cardiovascular, endocrine or metabolic diseases;
• Presence of neurological or musculoskeletal impairments at finger flexors muscles level;
• Pharmacological therapies in place that can affect the heart rate and the sleep quality;
• Self-declaration of pregnancy.

Anonymous individual participant data for all primary and secondary outcome measures will be made available

Data will be available within 6 months from the end of the study.

Data access request will be reviewed by the principal investigator and co-investigators.

Requestors will be required to sign a Data Access Agreement.