Jobs that require work outside the traditional daytime hours of approximately 8 AM to 6 PM have become ubiquitous across economically developed nations, but extensive research shows that shift work and long work hours may compromise employee health. Although employers recognize the potential harmful effects of shift work, many argue in favor of maintaining it, citing the nature of the work requiring a 24/7 schedule (e.g., public safety), maximization of production capacity in response to consumer demand, and in some cases, employee preference for long shifts to maximize days off and pay.

In recent publications, P4A researcher Megan McHugh, doctoral student Adovich Rivera, and their colleagues from Northwestern’s Manufacturing and Health Research Program provide evidence on how shift work affects the incidence of chronic illness and overall worker well-being.


The research team conducted systematic reviews of existing meta-analyses to assess the link between shift work or long work hours and chronic conditions. They found:

  • moderate-grade evidence linking shift work to breast cancer and long work hours to stroke; and
  • low-grade evidence suggesting an increased risk of depression, some forms of cardiovascular diseases, and complications of pregnancy with exposure to shift work or long work hours.

The National Institute for Occupational Safety and Health released a Framework for Worker Well-Being the identifies five domains that contribute to workers’ health and quality of life. Through focus groups with workers in the manufacturing industry who work 12-hour and rotating shifts, the researchers found that these work schedules were detrimental to four of the five domains: workplace physical environment and safety climate; health status; work evaluation and experience; and home, community, and society. For example, manufacturing workers found shift work to be stressful because it disrupts sleep patterns and makes it difficult to maintain social relationships. The exception was in the workplace policies and culture domain, as some workers described shift work as necessary, fair, and financially beneficial.

The researchers concluded that, overall, shift work and long work hours are detrimental to employee health and well-being.


Encouraging the elimination of shift work or long work hours is not a goal of this study; indeed, these schedules are largely inevitable in manufacturing and many other industries. However, both workers and employers should be informed of the potential immediate and long-term risks associated with jobs involving shift work or long work hours. Additionally, employers may seek out strategies to mitigate the risk for employees.

For example, additional screening and preventive measures for breast cancer and stroke may be warranted for shift workers and those who work 12-hour shifts. Additionally, results related to worker wellness suggest that traditional workplace wellness benefits (e.g., discounted gym memberships, smoking cessation programs), which have a dubious evidence base, are unlikely to address the challenges associated with shift work. Employers might consider adopting wellness benefits that transcend the boundaries of the traditional workplace, and that can support workers and their families. The US military offers several examples, such as on-site child care, commissaries, and leisure and recreation programs to save time and reduce family stress.

Related Evidence

  • Published August 10, 2020

    Despite extensive research showing that shift work compromises employee health, jobs that require work outside the traditional daytime hours of 8:00 AM to 6:00 PM have become ubiquitous across economically developed nations. Employers enact work scheduling policies based on the needs of company stakeholders and without evidence of the effect of shift work on health care costs, even though the companies ultimately bear the majority of those costs. Researchers Megan McHugh, Dustin D. French, Mary M. Kwasny, Claude R. Maechling, and Jane L. Holl examined the additional health care costs incurred by two large manufacturing companies due to their shift work requirements in this brief published in the Journal of Occupational and Environmental Medicine.

    View Evidence