Subjective and objective evaluation of sleep and performance in daytime versus nighttime sleep in extended-hours shift-workers at an underground mine

J Occup Environ Med. 2004 Mar;46(3):212-26. doi: 10.1097/01.jom.0000117421.95392.31.


Extended hours of shift work has the potential for adverse consequences for workers, particularly during the nightshift, such as poorer sleep quality during the day, increased worker fatigue, and fatigue-related accidents and decreased work performance. This study examined subjective and objective measurements of sleep and performance in a group of underground miners before and after the change from a backward-rotating 8-hour to a forward-rotating 10-hour shift schedule. The purpose of this study was to evaluate the short- and long-term impact of a shift schedule change on sleep and performance. The results demonstrated improved subjective and objective measures of sleep and performance on the new 10-hour nightshift schedule. The 10-hour nightshift workers subjectively reported more refreshing sleep, fewer performance impairments and driving difficulties than 8-hour nightshift workers. The results of the objective measures of sleep and performance on the 10-hour nightshifts were overall similar or possibly better than those measured on the 10-hour dayshifts. These are some of the first data to suggest that a nightshift that does not encompass the entire night period could have significant benefits to shift-workers. We suggest that these benefits are mostly the result of the timing of the new nightshift start and end times rather than other shift-schedule factors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Accidents, Occupational / prevention & control
  • Adult
  • Analysis of Variance
  • Fatigue / diagnosis*
  • Fatigue / physiopathology
  • Humans
  • Mining*
  • Occupational Diseases / diagnosis*
  • Occupational Diseases / physiopathology
  • Polysomnography
  • Risk Factors
  • Sleep Wake Disorders / diagnosis*
  • Sleep Wake Disorders / physiopathology
  • Surveys and Questionnaires
  • Task Performance and Analysis*
  • Work Schedule Tolerance*