Physiological and psychological indicators of stress in a longitudinal study of nurses in the workplace.
Physiological and psychological indicators of stress were measured in a cohort of 20
female nurses working 12 hour, 7.5 hour and 'nine to five' shift patterns in intensive
care units conducted over a period of four years. Saliva samples were collected by each
subject at four specified times during each shift over a period for one week and repeated
every few months. Two consecutive days were used to compare days on duty, days off
duty and the first day at work following days off.
Salivary cortisol levels were measured by RIA. Secretory immunoglobulin A (SIgA),
also a physiological indicator of stress, was determined with an indirect sandwich
ELISA using a monoclonal antibody. Salivary cortisol levels of nurses were higher and
SIgA levels lower prior to starting 12 hour shift following a day off compared with
nurses working other shifts. Simultaneous psychological measures obtained by selfreports
of perceived demands, coping and moods showed these nurses did not perceive
themselves to be stressed. The findings of the study suggest that nurses working 12 hour
shifts prepare for work differently perhaps in anticipation of long hours of work.
Furthermore, salivary cortisol levels were considerably higher compared with those cited
in studies of acute stress under laboratory conditions.
In contrast, 20 nurses undertaking an academic examination, considered an acute
stressful event, reported increased anxiety and mental and emotional demands and had
higher salivary cortisol concentrations prior to the event, albeit lower than the
longitudinal study. SIgA levels were lower prior to the examination but not significantly
so. A positive correlation between cortisol and SIgA levels was apparent, however, only
6 months later when the subjects no longer perceived themselves to be stressed.