The effect of twelve-hour shift working on absence attributed to sickness.

In a review of the medical and social aspects of shift work Taylor (1970) points out that many of the most important questions relating to shift work remain to be answered. One of these questions, on which evidence to date has been almost nonexistent, is the effect of a twelve-hour shift system on absence attributed to sickness. An opportunity to examine this occurred in 1973 when a change was made from an eight-hour to a twelve-hour shift work system by men employed as process workers in an oil refining and petrochemicals plant. Under the eight-hour system, in eight weeks a shift worker had six periods of seven consecutive eight-hour shifts, four periods of two consecutive days off, and two periods of three consecutive days off-that is, 42 days at work, 14 off, with an average working week of 42 hours. Under the twelve-hour system, in eight weeks a shift worker has seven periods of four consecutive twelve-hour shifts, and seven periods of four consecutive days off-that is, 28 days at work, 28 off, with the same average working week of 42 hours. Absence attributed to sickness is deemed to start on the first working day that a person is not at work and to end on the calendar day preceding return to work. A certificate to cover sickness absence is required after three days. Sick pay is paid for absence of both short and long duration. It includes the shift differential, which did not alter with the change in system.