Shiftwork - Fundamentals and Assessment Tools for Occupational Ergonomics - page 641

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Shiftwork

32.1 Introduction ............................. 32-1
32.2 Circadian Factors .......................... 32-2
32.3 Sleep Factors ............................. 32-4
32.4 Domestic Factors .......................... 32-6
32.5 Solutions . . . ............................. 32-6
32.6 Conclusions . ............................. 32-7

Timothy H. Monk
University of Pittsburgh Medical
Center

32.1 Introduction

The ergonomic problem with regard to shiftwork is that of enabling the individual to work at abnor-
mal hours, an activity which runs both counter to his or her own biology (Homo sapiens is a diurnal
species) and counter to the surrounding society which is structured to protect the sleep of day
workers, but not that of night workers, and expects evenings and weekends to be free for social, reli-
gious, athletic, and cultural events. Moreover, shiftwork is not simply restricted to a very small group
of people who can be carefully selected or self-selected to experience minimal problems. Neither is it
restricted to the youngest and fittest of workers who can bid their way out of abnormal hours when
they advance into their middle age. Employment trends, particularly in the manufacturing sector, now
dictate that the “bidding out of shiftwork by seniority” option often no longer applies. For many
middle-aged and late middle-aged workers the only option is between shiftwork and no work.
Thus, approximately one fifth of all employees are engaged in some form of work that requires
their presence outside of the “standard” 7 am to 6 pm working day on a regular basis, and can
thus be regarded as “shiftworkers.”
The proportion of the working population engaged in shiftwork can be expected to rise as second
jobbing and mandatory overtime increase. 1 The fastest growing sector of most Western economies is
the service sector, and people are increasingly demanding and receiving around the clock availability
of such services. Even in the production sector, plant machinery has become so expensive and so
quickly obsolete that it has to be run 24 h per day, 7 days per week, in order for it to be profitable. Also,
many nations have adopted taxation and business evaluation strategies (e.g., in assessing profitability
and providing health insurance) that encourage employers to squeeze as many work hours per year as
possible from their existing employees, rather than hiring new ones, as the volume of business increases.
This may lead to extended work weeks and fewer different work teams covering each 24-h day.
Some people cope well with shiftwork, others poorly. Moore-Ede 2 and others have referred to a shift-
work maladaptation syndrome in those failing to cope. As noted above, shiftwork intolerance stems pri-
marily from the fact that we are a diurnal species, designed to be asleep at night and alert and active
during the day, and that we have constructed a society which is built around this biological reality.

32-1