Shiftwork - health effects

There is increasing evidence becoming available that shift work can lead to very serious consequences.

Shift work can be described as any shift outside the normal daylight hours of 7am to 6pm.

Increasing research is linking  shift work to poorer sleep, circadian rhythm disturbances, and strains on family and social life. Night work and shift work have been linked to serious conditions from cancer to heart disease. Fatigue can be deadly. In our society it is not possible to eliminate shift work, and so it is necessary to develop strategies to make critical services available while keeping workers healthy and everyone around them safe.

In addition to more workers working shift work, there are growing numbers of workers working long hours on a regular basis - or others having to juggle more than one job over several parts of the day. Every extra hour on the job is one less spent someone's off-the-job responsibilities (eg with family). When the day is too full to fit everything in, it is often sleep that gets the short shrift.

The hours we work and the hours we sleep are a crucial health and safety issue.

Page Overview

Shift work disorder (SWD)

Shift work disorder (SWD), which is characterized by insomnia and excessive sleepiness related with shift work, is one of the most common health problems in shift workers.

Shift work disorder causes insomnia, fatigue, worse work performance, an increased likelihood of workplace incidents ('accidents'), and a poor quality of life. In addition, SWD is associated with decreased productivity and increased economic costs. The correct management of SWD is important to prevent sleep disturbances and maintain work performance in shift workers.

To diagnose and evaluate SWD, it is necessary to take detailed medical histories, assess the severity of sleep disturbances, and evaluate shift workers' sleep using a sleep diary and actigraphy (a non-invasive method of monitoring human rest/activity cycles). The work-fitness evaluation should include recommendations on how shift workers can reduce their sleep disturbances and increase work performance, as well as the assessment of work performance. A recent research paper reviews previous research on the evaluation, diagnosis, and management of SWD and summarizes the work-fitness evaluation of SWD. Read more: Tae-Won Jang: Work-Fitness Evaluation for Shift Work Disorder [Open access] Int. J. Environ. Res. Public Health 2021, 18(3), 1294;

Back to top

2015 Health Survey for England survey conducted by the Health and Social Care Information Centre

The results of this survey are as follows:

    • Shift workers have higher rates of obesity and ill-health than the general population.
      The data from the survey showed that 30% of shift workers were obese, compared with 24% of men and 23% of women working normal hours.
    • 40% of men and 45% of women on shifts had long-standing health conditions, such as back-pain, diabetes or chronic obstructive pulmonary disease, compared with 36% and 39% of the rest of the population.
    • 'Night owls' are also more likely to smoke, which could exacerbate many of the illnesses they are at risk of developing.
    • Shift work is most common in the 16-24 age group; an age group that should exhibit better levels of health and cognitive performance.
      The rates fell with age so that fewer than a third of men and a fifth of women were working shifts after the age of 55.

Back to top

US National Institute for Occupational Safety and Health (NIOSH) Work and Sleep Blog

What are the risks of long work hours and shift work?

Risks for Workers:

  • Sleep deprivation   
  • Lack of adequate time to recover from work
  • Decline in mental function and physical ability, including emotional fatigue and a decline in the function of the body's immune system 
  • Higher rates of depression, occupational injury, and poor perceived health
  • Higher prevalence of insomnia among shift workers with low social support
  • Increased risk of illness and injury
  • Strain on personal relationships, such as marriage and family life
  • Increased risk of long-term health effects, such as heart disease, gastrointestinal disorders, mood disturbances, and cancer

Risks for Employers:

  • Reduced productivity
  • Increase in errors
  • Absenteeism and presenteeism (present at work but not fully functioning because of health problems or personal issues) 
  • Increased health care and worker compensation costs
  • Workforce attrition due to disability, death, or moving to jobs with less demanding schedules

Risks to the Community:

Potential increase in errors by workers leading to:
  • Medical errors
  • Vehicle crashes
  • Industrial disasters
Read more:

Back to top

Canadian Institute for Work and Health

September, 2010

The Canadian Institute for Work and Health, an independent not-for-profit organisation whose mission is to conduct and share OHS research, has published an issues briefing on the impact of shift work on health. The research has noted some concerns involved with shift work.

The key messages from the research are:

    • People who work night shifts are likely to have shorter sleep duration and/or poorer sleep quality than regular day workers.
    • Long-term exposure to night shift work may elevate the risk of breast cancer. There are also findings pointing to an elevated risk of colorectal cancer.
    • Some studies indicate an elevated risk of preterm delivery, gastrointestinal disorders and mental health problems among shiftworkers.
    • Research findings regarding a causal link between shiftwork and heart disease are inconsistent.
    • Shiftworkers, especially those working at night, face a higher risk of workplace injury than regular day workers.
    • Promising approaches to mitigate the adverse effects of shiftwork include restricting successive evening or night.
    • Shifts to three shifts, limiting weekend work, moving from backward to forward shift rotation and using a participatory approach to the design of shift schedules.
    • More research is needed to resolve some of the questions regarding the health effects of shift work, and to investigate the impact of interventions designed to mitigate the adverse consequences of shiftwork on health.

Back to top

UK Trade Union Congress

In 2009 the UK peak union council, the TUC undertook a special report on Shiftwork: While you were sleeping, and published it in their Hazards Magazine  The report begins:

Shiftwork and work at night has been linked to a wide range of health problems, including breast cancer (1), prostate cancer (2), non-Hodgkin's lymphoma (3), heightened accident risk (4), heart disease risk factors (5) and pregnancy problems (6). There is emerging evidence that these health effects combined make shiftworkers, particularly women shiftworkers, far more likely to take early ill-health retirement (7).

The report provides a great background on what are non-typical hours, how shiftwork affects the body, the evidence of links between shiftwork and breast cancer, and heart disease, and reproductive health. It provides some advice on what to do at the workplace, facts and fiction around shiftwork and an "action plan" for reps. In addition, all the information is referenced.

Back to top

2021 Shift Work and Heart Problems Study

Long-term night shifts are “significantly associated” with heart-related health problems in UK workers, according to a 2021 study. Researchers from China, Hong Kong, the USA and Sweden examined UK data and found working late hours was linked with irregular and fast heart rate, with women potentially at greater risk.

Working night shifts also increased the risk of coronary heart disease (CHD), according to the paper published in the European Heart Journal. Researchers have previously looked how night shift work impacts health (Risks 891), including a 2018 study finding an increased risk of CHD from rotating shift patterns.

The authors of this study say they believe it is the first of its kind to test the association between night shift work and atrial fibrillation (AF) - a heart condition causing an irregular and often abnormally fast heart rate.  

The study - which used information from 283,657 people in the UK Biobank database - found “both current and lifetime night shift exposure were significantly associated” with a risk of atrial fibrillation regardless of genetics. The findings suggested that among people who worked an average of between three and eight night shifts a month for 10 years or more, the risk increased to 22 per cent compared with daytime workers.

Previous research has also found women who worked night shifts had an increased risk of developing type 2 diabetes, breast cancer (Risks 958), asthma (Risks 974) and faced a greater risk of miscarriage (Risks 891). Night shifts have also been linked to a higher risk of road traffic accidents while travelling home from a shift (Risks 808).
Read more: Ningjian Wang and others. Long-term night shift work is associated with the risk of atrial fibrillation and coronary heart disease, European Heart Journal, 2021;, ehab505. Published 10 August 2021. Independent.

Back to top


1. Sarah Megdala and others. Night work and breast cancer risk: A systematic review and meta-analysis, European Journal of Cancer, volume 41, issue 13, pages 2023-2032, 2005.

2. Tatsuhiko Kubo and others. Prospective cohort study of the risk of prostate cancer among rotating-shift workers: Findings from the Japan Collaborative Cohort Study, American Journal of Epidemiology, volume 164, pages 549-555, 2006.

3. T Lahti and others. Night-time work predisposes to non-Hodgkin lymphoma, International Journal of Cancer, volume 123, pages 2148–2151, 2008.

4. Kenneth N Fortson. The diurnal pattern of on-the-job injuries, Monthly Labor Review, pages 18-25, September 2004 [pdf].

5. Y Fujino and others. A prospective cohort study of shift work and risk of ischemic heart disease in Japanese male workers, American Journal of Epidemiology, volume 164, pages 128-135, 2006.

6. Lisa A Pompeii others. Physical exertion at work and the risk of preterm delivery and small-for-gestational-age birth, Obstetrics & Gynaecology, volume 106, pages 1279-1288, 2005 [abstract - full article can be downloaded from this page].

7. Finn Tüchsen, Karl Bang Christensen, Thomas Lund, and Helene Feveile. A 15 year prospective study of shift work and disability pension, Occupational and Environmental Medicine, volume 65, pages 283–285, 2008.

Last amended August 2021

Back to top