Shiftwork schedules: time of shift

Yesterday, I talked about the factors you need to consider when creating shiftwork schedules for a 24/7 shiftwork operation. Today, I'm talking about the time of day a shift is worked and the implications for shiftworkers.

Twenty-four hour operations usually are usually divided into two or three shifts. Start and end-times depend on the length of the shift.

• Day shift (also called morning or first shift) starts around 5 to 8 a.m. and ends around 2 to 6 p.m.
• Evening shift (also called afternoon or second shift) starts around 2 to 6 p.m. and ends around 10 p.m. to 2 a.m.
• Night shift (also called third, “graveyard shift,” or “mid” shift) starts around 10 p.m. to 2 a.m. and ends around 5 to 8 a.m.

A shiftwork schedule which calls for workers to work 12-hour shifts has two shifts per day – a day shift and a night shift.

Why is the time of shift important?
Because people who work in the late night or early morning hours often feel sleepy and fatigued during their shift. This happens because their body rhythm (also called a circadian rhythm) tells them to be asleep at those times.

Night workers also must sleep during the day, when their circadian rhythm tells them to be awake. Because of this, day sleep is short and feels “light” or unsatisfying. Often, night workers don't get enough sleep during the day to combat nighttime fatigue and sleepiness. Also, day workers sometimes must wake up very early to go to work. This might cause them to cut off their sleep, which makes them feel tired during the day.

Shiftwork schedule times also determine when a worker can see family and friends. Many social events take place in the evening, which means they might be missed by evening or night workers. Parents who work the evening shift might not see their children during the week because they are at work when the kids return from school. If this happens too often, it can be stressful.

In future posts, I'll talk about the other factors to consider when creating a shiftwork schedule or rota -- length of shift, start times, direction of rotation, rotation schedules, etc.

Source: Plain Language About Shiftwork (NIOSH)