Shift work is an employment practice designed to keep a service or production line operational at all times. The practice typically sees the day divided into shifts, set periods of time during which different groups of workers perform their duties. The term "shift work" includes both long-term night shifts and work schedules in which employees change or rotate shifts.
In medicine and epidemiology, shift work is considered a risk factor for some health problems in some individuals, as disruption to circadian rhythms may increase the probability of developing cardiovascular disease, cognitive impairment, diabetes, altered body compositionSooriyaarachchi P, Jayawardena R, Pavey T, King N. Shift work and body composition: a systematic review and meta-analysis. Minerva Endocrinology. 2021 Jun.https://doi.org/10.23736/s2724-6507.21.03534-x and obesity, among other conditions.
Shift schedule and shift plan
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. The most common plan for eight-hour workdays is the three-shift plan, where each day is divided into three eight-hour blocks, with the first shift beginning in the morning, and each worker works during the same block every workday.
Rotation of shifts can be fast, in which a worker changes shifts more than once a week, or slow, in which a worker changes shifts less than once a week. Rotation can also be forward, when a subsequent shift starts later, or backward, when a subsequent shift starts earlier. Evidence supports forward rotating shifts are more adaptable for shift workers' circadian physiology.
One main concern of shift workers is knowing their schedule more than two weeks at a time. Shift work is stressful. When on a rotating or ever changing shift, workers have to worry about daycare, personal appointments, and running their households. Many already work more than an eight-hour shift. Some evidence suggests giving employees schedules more than a month in advance would give proper notice and allow planning, their stress level would be reduced.
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. Eight-hour shifts and twelve-hour shifts are common in manufacturing and health care. Twelve-hour shifts are also used with a very slow rotation in the petroleum industry. Twenty-four-hour shifts are common in health care and emergency services.
Management
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. Multiple factors need to be considered when developing optimal shift work schedules, including shift timing, length, frequency and length of breaks during shifts, shift succession, worker commute time, as well as the mental and physical stress of the job. These practices and policies can include selecting an appropriate shift schedule or rota and using an employee scheduling software to maintain it, setting the length of shifts, managing overtime, increasing lighting levels, providing shift worker lifestyle training, retirement compensation based on salary in the last few years of employment (which can encourage excessive overtime among older workers who may be less able to obtain adequate sleep), or screening and hiring of new shift workers that assesses adaptability to a shift work schedule. Mandating a minimum of 10 hours between shifts is an effective strategy to encourage adequate sleep for workers. Allowing frequent breaks and scheduling 8- or 10-hour shifts instead of 12-hour shifts can also minimize fatigue and help to mitigate the negative health effects of shift work. Even though studies support 12-hour shifts are associated with increased occupational injuries and accident (higher rates with subsequent, successive shifts), a synthesis of evidence cites the importance of all factors when considering the safety of a shift.
Algorithmic scheduling of shift work can lead to what has been colloquially termed as "clopening" where the shift-worker has to work the closing shift of one day and the opening shift of the next day back-to-back resulting in short rest periods between shifts and fatigue. Co-opting employees to fill the shift roster helps to ensure that the human costs are taken into account in a way which is hard for an algorithm to do as it would involve knowing the constraints and considerations of each individual shift worker and assigning a cost metric to each of those factors. Shift based hiring which is a recruitment concept that hires people for individual shifts, rather than hiring employees before scheduling them into shifts enables shift workers to indicate their preferences and availability for unfilled shifts through a shift-bidding mechanism. Through this process, the shift hours are evened out by human-driven market mechanism rather than an algorithmic process. This openness can lead to work hours that are tailored to an individual's lifestyle and schedule while ensuring that shifts are optimally filled, in contrast to the generally poor human outcomes of fatigue, stress, estrangement with friends and family and health problems that have been reported with algorithm-based scheduling of work-shifts.
History
The shift work system in modern industrial manufacturing originated in the late 18th century.
In 1867, Karl Marx wrote on the shift work system in Capital, Volume 1: Capitalist production therefore drives, by its inherent nature, towards the appropriation of labour throughout the whole of the 24 hours in the day. But since it is physically impossible to exploit the same individual labour-power constantly, during the night as well as the day, capital has to overcome this physical obstacle. An alternation becomes necessary, between the labour-powers used up by day and those used up by night ... It is well known that this shift-system, this alternation of two sets of workers, predominated in the full-blooded springtime of the English cotton industry, and that at the present time it still flourishes, among other places, in the cotton-spinning factories of the Moscow gubernia. This 24-hour process of production exists today as a system in many of the as yet 'free' branches of industry in Great Britain, in the blast-furnaces, forges, rolling mills and other metallurgical establishments of England, Wales and Scotland.Marx, Karl. "The Working Day" Capital: Volume 1, 1867.
The Cromford Mill, starting from 1772, ran day and night with two twelve-hour shifts.
Shift work was once characteristic primarily of the manufacturing industry, where it has a clear effect of increasing the use that can be made of capital equipment and allows for up to three times the production compared to just a day shift. It contrasts with the use of overtime to increase production at the margin. Both approaches incur higher wage costs. Although 2nd-shift worker efficiency levels are typically 3–5% below 1st shift, and 3rd shift 4–6% below 2nd shift, the productivity level, i.e. cost per employee, is often 25% to 40% lower on 2nd and 3rd shifts due to fixed costs which are "paid" by the first shift.Alan Blinder and William Baumol 1993, Economics: Principles and Policy, Harcourt Brace Jovanovich, San Diego, p. 687.
Adoption It is estimated that 15–20% of workers in industrialized countries are employed in shift work. Shift work is common in the transportation sector as well. Some of the earliest instances appeared with the railroads, where freight trains have clear tracks to run on at night.
Shift work is also the norm in fields related to public protection and healthcare, such as law enforcement, emergency medical services, firefighting, security and hospitals. Shift work is a contributing factor in many cases of medical errors. Shift work has often been common in the armed forces. Military personnel, pilots, and others that regularly change time zones while performing shift work experience jet lag and consequently suffer sleep disorders.
Those in the field of meteorology, such as the National Weather Service and private forecasting companies, also use shift work, as constant monitoring of the weather is necessary. Much of the Internet services and telecommunication industry relies on shift work to maintain worldwide operations and uptime.
Service industries now increasingly operate on some shift system; for example a restaurant or convenience store will normally be open on most days for much longer than a working day.
There are many industries requiring 24/7 coverage that employ workers on a shift basis, including:
Caregiver Direct support professional Customer service, including call centers Data center and IT operations Death care (medical examiner or coroner) Emergency services Police Firefighting Emergency medical services Entertainment Casino workers Health care Funeral workers Hospitality Logistics and transportation Railways Ship crew Manufacturing Flight testing Military Mining Public utilities Nuclear power Fossil fuel Solar, wind, and hydro power Retail Telecommunications Television Radio broadcasting Security Weather
Health effects
Shift work increases the risk for the development of many disorders.
Sleep disorders
Shift work increases the risk of sleep 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 health consequences of shift work may depend on chronotype, that is, being a day person or a night person, and what shift a worker is assigned to. When the individual's chronotype is the opposite of shift timing (e.g., a day person working night shift), there is a greater risk of circadian rhythm disruption.
Artificial lighting may additionally contribute to disturbed homeostasis.
Nighttime workers sleep an average of one to four hours less than daytime workers.
Hormonal and endocrine problems The risk of diabetes mellitus type 2 is increased in shift workers, especially men. People working rotating shifts are more vulnerable than others.
Working rotating shift work regularly during a two-year interval has been associated with a 9% increased the risk of early menopause compared to women who work no rotating shift work. The increased risk among rotating night shift workers was 25% among women predisposed to earlier menopause. Early menopause can lead to a host of other problems later in life. A recent study, found that women who worked rotating night shifts for more than six years, 11% experienced a shortened lifespan.
Shift work increases the risk of obesity, metabolic disorders, gastrointestinal disorders, musculoskeletal disorders, and reproductive disorders. Muscle health is also compromised by shift work: altered sleep and eating times, changes to appetite-regulating hormones and total energy expenditure, increased snacking and binge drinking, and reduced protein intake can contribute to negative protein balance, increases in insulin resistance and increases in body fat, resulting in weight gain and more long-term health challenges.
Cancer