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How shift work disrupts workers’ health and lives

[fa icon="calendar"] 2/14/18 4:55 PM / by SAMTRAC


Cover image 14 February 2018.jpg

Despite a century-long optimism about reducing the number of working hours and considerable progress in legal measures limiting working hours, the differences in actual working hours between industrialised and developing countries remain considerable – without any clear sign of hours being reduced. In fact, with work space and time becoming more flexible, people appear to be working a greater number – not fewer – hours.


According to an editorial in the March 2010 issue of the Scandinavian Journal of Work and Environmental Health, shift work is ‘…one of the most serious occupational health problems of our time’. We cannot continue to ignore taking preventative and curative public health actions in anticipation of further data.


What is shift work?

A standard work day consists of a shift scheduled between 07h00 and 18h00. Shift work can be defined as work scheduled outside of these ‘normal’ hours. Examples include:

  • evening schedule (beginning after 15h00 and ending before 00h00);
  • night schedule (beginning after 23h00 and ending before 11h00);
  • rotating shift schedule (day, afternoon/evening, night);
  • split shifts (two scheduled periods of work each day);
  • being on call; and
  • an irregular schedule.


In 2005, the International Labour Organization (ILO) reported the average number of weekly working hours among a variety of developed and developing countries:

  No universal statutory limit 35–39 hours 40 hours 41–46 hours 48 hours More than 48 hours
Industrialised countries Australia, Denmark, Germany, Ireland, United Kingdom (48-hour limit on total hours) Belgium, France Austria, Canada, Finland, Italy, Japan, Luxembourg, Netherlands, New Zealand, Norway, Portugal, Spain, Sweden, United States Switzerland (workers in industrial enterprises, offices, technical posts and sales staff in large commercial enterprises)   Switzerland (all other workers)
Africa Nigeria, Seychelles Chad Algeria, Benin, Burkina Faso, Cameroon, Congo, Côte d’Ivoire, Djibouti, Gabon, Madagascar, Mali, Mauritania, Niger, Rwanda, Senegal, Togo Angola, Burundi, Cape Verde, Democratic Republic of Congo, Guinea-Bissau, Morocco, Namibia, South Africa, United Republic Tanzania Mozambique, Tunisia Kenya
Asia India, Pakistan   China, Indonesia, Republic of Korea, Mongolia Singapore Cambodia, Lao People’s Democratic Republic, Malaysia, Philippines, Thailand, Vietnam  
Caribbean Jamaica, Grenada   Bahamas Cuba, Dominican Republic Haiti  
Central and Eastern Europe     Bulgaria, Czech Republic, Estonia, Latvia, Lithuania, the former Yugoslav Republic of Macedonia, Romania, Russian Federation, Slovakia, Slovenia      
Latin America     Ecuador Belize, Brazil, Chile, El Salvador, Honduras, Uruguay (commerce), Venezuela Argentine, Bolivia, Colombia, Costa Rica, Guatemala, Mexico, Nicaragua, Panama, Paraguay, Peru, Uruguay (industry)  
Middle East     Egypt   Jordan, Lebanon  


4 ways shift work affects worker health

The human body functions according to a natural sleep-wake/day-night 24 hour cycle referred to as a circadian rhythm. This rhythm helps to maintain most internal functions, ranging from body temperature and hormone levels, to blood pressure and sleep/wake patterns. It is guided by environmental cues such as darkness and light and day and night. Shift work, particularly involving work at night, disrupts the circadian rhythm. This disruption has been linked with cancer and a range of other health and social impacts in shift workers.



The International Agency for Research on Cancer (IARC) has designated shift work involving circadian rhythm disruption as ‘probably carcinogenic to humans’ (Group 2A). In their findings, IARC cited studies of nurses and female flight attendants who developed excess levels of breast cancer. Studies have also found elevated risks of prostate, colorectal and endometrial cancers for shift workers. In 2009, the Danish National Board of Industrial Injuries became the first compensation system in the world to recognise the link between working night shifts and the development of breast cancer.


Workplace injuries

Research suggest night, evening, rotating and irregular shifts are all linked with an elevated risk of workplace incidents resulting in injuries. According to Ontario’s Institute for Work and Health (IWH), evidence suggests six to seven per cent of workplace injuries can be attributed to the higher risk of injury associated with risk work. The Institute’s same study found that the risk is more pronounced for women, as women are more likely to be responsible for childcare and household work, and therefore have more difficulty adjusting to shift work and maintaining regular sleep schedules.


Mental health and work-life balance

Anxiety, depression and stress are just some of the mental health issues reported by shift workers. Working shifts can also complicate family, social and community life. Most social activities are scheduled at night or on weekends – times when shift workers may be working. Scheduling ‘quality’ time with a spouse or children may be difficult. Fatigue may also impact ‘quality’ time. Shift workers experience higher divorce rates compared to workers employed on day shifts.


Other health effects

A 2012 study found shift work was associated with:

  • a 23 per cent increased risk of a heart attack
  • a 24 per cent increased risk of a coronary event, and
  • a five per cent increased risk of having a stroke.


Shift work is also linked with reproductive health problems including excess risk of:

  • miscarriages
  • pre-term delivery
  • low birth weight, and
  • delayed foetal development.


Studies have found shift workers also suffer from excess gastrointestinal disorders, including ulcers and heartburn. Shift work has also been linked to excess diabetes. Violence or its potential is also a concern for shift workers who work alone or in other vulnerable situations.


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