What are shift work and night work?
Sectors such as healthcare, continuous process manufacturing, transportation, security, hospitality, and emergency services need to cover operations beyond the daytime hours. Shift work (rotating, fixed, morning, afternoon, and night shifts, in cycles of varying duration) and night work are the organizational solution, but they come at a cost to people’s health and lives: the human body is programmed for daytime activity and nighttime rest, and working against this rhythm leads to sleep disturbances, chronic fatigue, digestive and cardiovascular disorders, an increased risk of accidents due to drowsiness, and difficulties in balancing work and family life. The Epworth Sleepiness Scale can be used to screen for daytime sleepiness in health surveillance , but it does not, on its own, determine fitness for the job.
The Workers’ Statute establishes basic rules: the working day of night workers cannot exceed an average of eight hours per day over a reference period of fifteen days; these workers cannot work overtime; night work has specific remuneration unless it is compensated with rest periods or the salary has been established taking into account its nighttime nature; in rotating shifts, no worker can be on the night shift for more than two consecutive weeks except by voluntary assignment; and night workers must enjoy a level of safety and health protection adapted to the nature of their work, with free health assessments before the onset of illness and at regular intervals.
From a preventative standpoint, shift work and night work are psychosocial and organizational risk factors that must be assessed (Law 31/1995, Articles 4.7 and 16) and managed using ergonomic and chronobiological criteria, such as those described in INSST Technical Note 455. Directive 2003/88/EC on the organization of working time constitutes the European framework.
Effects on health and safety
- Circadian rhythm disruption. Mismatch between the biological clock and work schedule, with shorter and poorer quality daytime sleep, nighttime sleepiness, and accumulated fatigue.
- Physical health. Digestive disorders due to irregular meal times, increased cardiovascular and metabolic risk, and association with certain long-term health problems.
- Mental and social health. Irritability, anxiety, work-life balance difficulties, social isolation, and family conflicts.
- Safety. Reduced performance and attention during off-peak hours (early morning), with an increase in errors and accidents, including traffic accidents at the end of the night shift.
- Vulnerable groups. Older people, people with certain illnesses, or those who are pregnant or breastfeeding, for whom the regulations provide for adaptation or exemption from night work.
Preventive organization criteria
- Rotation design. Short rotations (two or three days) and clockwise (morning, afternoon, night) are better tolerated; avoid more than three consecutive nights and ensure sufficient rest after the night shift.
- Schedules. Avoid very early starts to the morning shift, maintain regular and predictable schedules, and allow some participation in the selection.
- Breaks and rest periods. Sufficient breaks for meals at reasonable times, the possibility of resting at night when the activity allows, and grouped days off.
- Workload. Reduce the most demanding or risky tasks during off-peak hours and adjust night shifts.
- Environment. Adequate lighting at night, temperature and food services available.
- Health monitoring and training. Specific check-ups, information on sleep hygiene, nutrition and driving after the shift, and attention to signs of intolerance.
Organizational application: how to manage shifts and night work
- Include shift and night work in the assessment of psychosocial and organizational risks, with data on absenteeism, accidents by time slot and staff perception.
- Design the shift system using chronobiological criteria (short and forward rotation, limit on consecutive nights, sufficient rest periods) and consult with the representatives.
- Adjust the workload and critical tasks on the night shift and ensure adequate staffing and supervision.
- Apply the limits of the Workers’ Statute: night shift, overtime, maximum stay and compensation.
- Organize specific health monitoring before and periodically after assignment, and manage adaptations for people with intolerances, older age, pregnancy or breastfeeding.
- Training in sleep hygiene, nutrition, driving after shift work, and fatigue detection.
- Measure and review: indicators of accidents and incidents per shift, absenteeism, turnover and satisfaction with the system.
Preventive management software allows you to link shifts with accident rates and absenteeism, plan specific health monitoring, and record adaptations and consultations with representatives.
Limits and common mistakes
- Designing shifts based solely on production criteria, without considering physiological tolerance or consulting the staff.
- Exceeding the maximum night shift or assigning overtime to night workers.
- Maintaining long or backward rotations hinders the adaptation of the circadian rhythm.
- Not offering prior and periodic health assessments or managing detected intolerances.
- Concentrating critical or maintenance tasks in the early morning without reinforcement or supervision.
- Forget the risks of driving home after the night shift.
Specific limits may be expanded or modified by collective agreement and sectoral regulations; this sheet is for informational purposes only.
Practical example
Situation: A continuous process plant with 240 people in five shifts reviews its system after an increase in early morning incidents.
- Analysis. Incidents are concentrated between three and six in the morning on the third consecutive night of the cycle; the system rotates backward and the morning shift begins at five.
- Redesign. Forward rotation with a maximum of two consecutive nights, morning shift starting at six and three days of rest after the nights, in consultation with the committee.
- Complementary measures. Rescheduling critical maintenance tasks to the afternoon shift, early morning rest breaks, and increased lighting in control areas.
- Monitoring. Specific health surveillance, sleep hygiene training and quarterly incident indicators by time slot.
Regulatory framework in Spain
- Royal Legislative Decree 2/2015, Workers’ Statute, Article 36. Night work, shift work and work rhythm: definitions, limits and health protection.
- Law 31/1995, articles 4.7, 15, 16, 22, 25 and 26. Working conditions, adaptation of work to the person, evaluation, health surveillance and protected groups.
- NTP 455 of the INSST . Shift and night work: organizational aspects.
- Directive 2003/88/EC of the European Parliament and of the Council of 4 November 2003. Organization of working time: night work, shift work and work pace.
ILO Convention 171 on night work establishes measures for the protection of health and maternity. In Colombia, the Substantive Labor Code regulates night shift differentials, and the Occupational Health and Safety Management System (SG-SST) requires the evaluation of risks arising from the organization of working time.
