Shift work

Shift work

‘The term shift work is defined as an arrangement of working hours that uses two or more teams (shifts) of workers, in order to extend the hours of operation of the work environment beyond that of the conventional office hours. The varieties of shift work include: stable/permanently displaced working hours in which the work schedule used does not require a person to normally work more than one shift (including night work), rotating shift work in which an individual is normally required to work more than one shift, changing from one shift to another and unscheduled working hours. On-call shift is also a special form of shift work, where in case of emergency the particular group of workers are called for their duties. The most widespread shift system is when production is organized in eight-hour shifts, called morning, evening and night shifts.’

According to the International Labour Office, shift work is defined as: ‘A method of work organization under which groups or crews of workers succeed each other at the same workstations to perform the same operations, each crew working a certain schedule or shift so that the undertaking can operate longer than the stipulated weekly hours for any worker. Often the term is used when more than one work period is scheduled in a workday or when most of the working hours fall outside the standard workday, such as evening, night or weekend shifts’.

Health effects

Several studies have been made on the problems of shift workers in relation to three important modulatory factors, namely circadian, sleep and social/psychosocial/domestic factors. These factors have been considered to be important in determining the coping ability of a worker to shift work.

Shift work increases the risk for the development of many disorders. Shift work sleep disorder is a circadian rhythm sleep disorder characterized by insomnia, excessive sleepiness, or both. Shift work is considered essential for the diagnosis. The risk of diabetes mellitus type 2 is increased in shift workers, especially men. People working rotating shifts are more vulnerable than others.

Acute sleep deprivation occurs during long shifts with no breaks, as well as during night shifts when the worker sleeps in the morning and is awake during the afternoon, prior to the work shift. A night shift worker with poor daytime sleep may be awake for more than 18 hours by the end of his shift. The change in sleep pattern leads to risk of developing cluster headaches, heart attacks, fatigue, stress, sexual dysfunction, depression, dementia, obesity, metabolic disorders, gastrointestinal disorders, musculoskeletal disorders, and reproductive disorders.

Intolerance to shift work

The severity of clinical problems may have varying magnitudes among individual shift workers. In other words, while some workers tolerate shift work better, others are intolerant. On the basis of intensity of medical complications, it is possible to classify shift workers having good tolerance (with neither complaints nor medical problems), poor tolerance (with medical complaints) and very poor tolerance (severe clinical problems). Clinical intolerance to shift work was defined by the existence and intensity of a set of medical complaints: (i) sleep alterations; (ii) persisting fatigue; (iii) changes in behaviour; (iv) digestive troubles and (v) The regular use of sleeping pills. Symptoms (i), (ii) and (v) are present in any intolerant subject. Clinical intolerance to shift work appears to be independent of an individual’s age and length of shift working experience.

Safety and regulation

Shift work has been shown to negatively affect workers, and has been classified as a specific disorder (shift work sleep disorder). Circadian disruption by working at night causes symptoms like excessive sleepiness at work and sleep disturbances. Shift work sleep disorder also creates a greater risk for human error at work. Shift work disrupts cognitive ability and flexibility and impairs attention, motivation, decision making, speech, vigilance, and overall performance.

In order to mitigate the negative effects of shift work on safety and health, many countries have enacted regulations on shift work. The European Union, in its directive 2003/88/EC, has established a 48-hour limit on working time (including overtime) per week; a minimum rest period of 11 consecutive hours per 24-hour period; and a minimum uninterrupted rest period of 24 hours of mandated rest per week (which is in addition to the 11 hours of daily rest). The EU directive also limits night work involving "special hazards or heavy physical or mental strain" to an average of eight hours in any 24-hour period. 

Prevention

• The practices and policies put in place by managers of round-the-clock or 24/7 operations can significantly influence shift worker alertness (and hence safety) and performance.
• The 42-hour work-week allows for the most even distribution of work time. A 3:1 ratio of work days to days off is most effective for eight-hour shifts, and a 2:2 ratio of work days to days off is most effective for twelve-hour shifts.
• The shift plan or rota is the central component of a shift schedule. The schedule includes considerations of shift overlap, shift change times and alignment with the clock, vacation, training, shift differentials, holidays, etc., whereas the shift plan determines the sequence of work and free days within a shift system.