Types of shiftwork

Longer shifts of 9 to 12 hours increase the working day, but these are usually worked on only 3 or 4 days a week, instead of 5 or 6. This is a popular way of working as it seems that there is extra free time every week.

Shifts can be fixed so that you work the same hours at the same time every day over a long period.

Shifts can also rotate, so that your hours change according to a pre-set sequence over a period. A rotating shift has a pattern that follows a certain speed and direction. The speed is the number of shifts that you work at a particular start time, before you change to another start time. The direction can be ' forward' - mornings, then afternoons, then nights; or ' backward' - nights, then afternoons, then mornings. So, if you were working on a forward rotating shift, you would work mornings for, say, a week, then afternoons for the next week, then nights for the next  week, and then back to mornings again.

A common 3-shift rotating system is:

Effects on human beings

As a human being, you have a 'daily body clock' or circadian rhythm (animals have this too). Your temperature, heart rate, blood pressure and mental ability are synchronised so that they are higher during daylight hours than at night, when the body is prepared to sleep and recover from the day's activities. Even if the normal influences of day and night are taken away, such as natural light and knowledge of the time, this internal clock still works and operates a cycle of between 22 and 25 hours.

We all need a period of undisturbed sleep to keep our health and well-being. An adult human needs about 8 hours' sleep per night, although there are big variations between individuals. How many hours of sleep do you and your friends need (honestly!)? Is it the same as adults that you know? There may well be a difference as length of sleep needed is mainly down to your age. A baby needs 15-17 hours of sleep every day during its first six months, but old people sleep less and less and it is often broken up into short naps.

Night workers often suffer from disturbed daytime sleep, which may be due to increased noise, but it is more likely due to the body just not being ready to sleep during the day. This lack of good quality sleep among night workers can lead to chronic fatigue, which can be shown as tiredness, irritability and depression. They may also suffer from loss of appetite and digestive problems. These symptoms quickly disappear when they return to normal work and sleep patterns.

Workers on late or night shifts often feel isolated from their family and friends because they are working when others are socialising. Family life can be difficult.

About two-thirds of shift workers suffer from some kind of ill-health, and about one-quarter have to give up shiftwork because of major health problems.

There is no single, optimum shift system. The design of a shift systems is usually driven by a number of factors, including legislation about daily working hours and the Working Time Directive, and agreements among the workforce. The most important requirements from a human point of view, is that loss of sleep should be as little as possible, and there should be enough time for family and social contact.

Legal requirements for working time

The Working Time Regulations (WTR) came into force on 1 October 1998. The Regulations implement the European Working Time Directive and parts of the Young Workers Directive which relate to the working time of adolescent workers (workers above the minimum school leaving age but below 18). Certain sectors are excluded from the scope of the Regulations.

Guidelines for shiftwork design

Night work is not recommended, but if it cannot be avoided, then the following guidelines should be considered:

• Ideally, night shift workers should be not be younger than 25 or older than 50 years of age.
• Build in single night shifts rather than consecutive ones, as the circadian rhythm is not significantly altered by a single night shift.
• Plan at least 24 hours free time after each night shift for workers to catch up on sleep.
• Maintain a quickly rotating shift system rather than a slow one, to reduce the number of similar consecutive shifts.
• Operate a forward rotation of shift.
• Extended work days of 9 to 12 hour shifts should only be considered if the nature of the work and work load are light, adequate time off is given, and sickness/absence cover is provided.
• Consider a 07:00-15:00-23:00 or 08:00-16:00-24:00 shift pattern.
• Limit consecutive work days to 5-7, with occasional free weekends and at least 2 consecutive days off to aid recovery.
• Include at least one hot meal break per shift.