SHIFTWORK EFFECTS IN NUCLEAR-POWER WORKERS - A FIELD-STUDY USING PORTABLE COMPUTERS

This field study of nuclear power shiftworkers reports the use of hand -held computers to record alertness levels, cognitive task performance and workload ratings. Subjective ratings and performance tasks (Searc h and Memory-5 (SAM-5); Choice Reaction Time (CRT)) were completed on the computers at 2-h intervals during selected shifts in the work sche dule by maintenance crews and reactor operators. Sleep duration and qu ality data were also obtained during the 35-day shift cycle. Workload remained relatively stable across shifts. The night-shift was associat ed with shorter sleep durations and poorer sleep quality. Significantl y lower levels of alertness and poorer performance for components of t he performance tasks were also observed on the night-shift. Time-on-sh ift effects on alertness were evident, whereby for the night-shift, es pecially, alertness dropped dramatically during the early hours. Compo nents of SAM-5 performance showed differential time-on-shift patternin g relative to each shift whereas CRT was unresponsive to time-on-shift effects. Significant variations were observed in alertness and perfor mance components during the 12-h night-shift. Perhaps paradoxically, p erformance on the 12-h night-shift appeared to improve rather than det eriorate during the early-hour period that was associated with the gre atest drop in alertness. This was suggestive of extra effort expenditu re during this critical period.