Shift work

Lore & Background

Shift work is an employment practice designed to maintain continuous operation of a service or production line by dividing the day into set periods, with different groups of workers performing duties during each period. This practice includes both long-term night shifts and schedules where employees rotate shifts. The shift plan, or rota, is the central component of a schedule, determining the sequence of work and free days. The most common arrangement for eight-hour workdays is the three-shift plan, where each day is split into three eight-hour blocks, with the first shift starting in the morning.

Rotation can be fast (changing shifts more than once a week) or slow (less than once a week), and forward (starting later) or backward (starting earlier); forward rotation is considered more adaptable for workers’ circadian physiology. Eight-hour and twelve-hour shifts are common in manufacturing and health care, while twenty-four-hour shifts are typical in health care and emergency services. A 3:1 ratio of work days to days off is effective for eight-hour shifts, and a 2:2 ratio for twelve-hour shifts.

Management practices, such as mandating a minimum of ten hours between shifts, scheduling frequent breaks, and using eight- or ten-hour shifts instead of twelve-hour shifts, can reduce fatigue and mitigate negative health effects. Algorithmic scheduling can lead to “clopening,” where a worker closes one day and opens the next with insufficient rest. Shift-based hiring, which hires people for individual shifts via a bidding mechanism, allows workers to indicate preferences and can tailor hours to individual lifestyles. In medicine and epidemiology, shift work is considered a risk factor for health problems, including cardiovascular disease, cognitive impairment, diabetes, altered body composition, and obesity, due to disruption of circadian rhythms.

Reader's Guide

The shift plan or rota is the central component of a shift schedule. The most common plan for eight-hour workdays is the three-shift plan. Rotation of shifts can be fast or slow, and forward or backward. Evidence supports forward rotating shifts are more adaptable for shift workers' circadian physiology.

Mandating a minimum of 10 hours between shifts is an effective strategy to encourage adequate sleep. Allowing frequent breaks and scheduling 8- or 10-hour shifts instead of 12-hour shifts can minimize fatigue. Twelve-hour shifts are associated with increased occupational injuries and accidents.