Shift work

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.

[1][2][3] 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 composition[4] and obesity, among other conditions.

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.

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.

[10] Women whose work involves night shifts have a 48% increased risk of developing breast cancer.

[11][12] This may be due to alterations in circadian rhythm: melatonin, a known tumor suppressor, is generally produced at night and late shifts may disrupt its production.

[12] The WHO's International Agency for Research on Cancer listed "shift work that involves circadian disruption" as probably carcinogenic.

The increased risk among rotating night shift workers was 25% among women predisposed to earlier menopause.

[16][17] A recent study, found that women who worked rotating night shifts for more than six years, eleven percent experienced a shortened lifespan.

Women who worked rotating night shifts for more than 15 years also experienced a 25 percent higher risk of death due to lung cancer.

Some shift patterns can exacerbate fatigue by limiting rest, increasing stress, overworking staff or disrupting their time off.

[37] Shift work disrupts cognitive ability and flexibility and impairs attention, motivation, decision making, speech, vigilance, and overall performance.

[37][38] 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.

[37][38] The EU directive allows for limited derogations from the regulation, and special provisions allow longer working hours for transportation and offshore workers, fishing vessel workers, and doctors in training (see also medical resident work hours).

[9] The Alaska Oil Spill Commission's final report on the Exxon Valdez oil spill disaster found that it was "conceivable" that excessive work hours contributed to crew fatigue, which in turn contributed to the vessel's running aground.

[42] 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.

When on a rotating or ever changing shift, workers have to worry about daycare, personal appointments, and running their households.

[11] Free online training programs are available to educate workers and managers about the risks associated with shift work and strategies they can use to prevent these.

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.

[57][58] Mental (cognitive) fatigue due to inadequate sleep an/or disturbances of circadian rhythms is a common contributor to accidents and untoward incidents.

[60][61] One method used within an FRMS is objective fatigue modeling to predict periods of high risk within a 24-hour shift plan.

Zopiclone has also been investigated as a potential treatment, but it is unclear if it is effective in increasing daytime sleep time in shift workers.

An especially high prevalence of short sleep duration was reported by night shift workers in the transportation and warehousing (69.7%) and health-care and social assistance (52.3%) industries.

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.

Military personnel, pilots, and others that regularly change time zones while performing shift work experience jet lag and consequently suffer sleep disorders.

Much of the Internet services and telecommunication industry relies on shift work to maintain worldwide operations and uptime.