| Author, Date |
Sample |
Description of Work Schedule |
Health or Safety Measure |
Statistical Methods Controls |
Results Reported by Authors |
| Axelsson et al.1998 |
28 power plant workers:
- Gender/age not clearly reported for performance testing
- Sweden |
3-shift fast forward rotation with 8-h shifts Monday to Thursday, 12-h shifts Friday to Sunday (4 - 7 on, 2 - 10 off), M 35 h/wk |
Simple reaction time and 10 minute vigilance tests compared 8-h and 12-h shifts at the beginning and end of 3 day shifts and 3 night shifts |
Repeated measures ANOVA with Huynh-Feldt epsilon correction method |
No significant performance differences between 8-h and 12-h shifts on simple reaction time tests and vigilance tasks. |
| Brake and Bates 2001 |
- 45 male underground miners acclimatized to hot work environment
- 15 controls in sedentary thermo neutral conditions
- Australia |
- First summer worked 6-h shifts
- Intervention during next summer was self-paced 10-h, 12-h, or 12.5-h shifts
- Data collected during day and night shifts, but did not report time-of-day effects
- Work h/wk not reported |
Pre- and post-intervention at shift start, middle, and end for several shifts collected continuous heart rate:
- Polar ECG-type recorders
- Cycle ergometer heart rates with pedal rate = 50 rpm at 100 Watts. |
Student's t-test |
- No significant changes in full shift continuous heart rate reported between 6-h shifts and self-paced extended shifts.
- Cycle ergometer heart rate showed significant increase between start and end of shift (p< .01).
- In 24 workers measured at start, middle, and end of extended shifts, ergometer heart rate showed significant increase between shift start and mid-shift (P=0.001), followed by significant decrease between mid-shift and shift end (p=0.04). |
| Hanecke et al. 1998 |
1.2 million workers' compensation records for "accidents" at work:
- Gender/age not reported
- Germany |
1994 Workers compensation records:
- Hour at work when "accident" occurred: 1st to 12th hour, > 12th hour
- Time of day "accident" occurred
- Interaction: time of day by hour at work |
- 1994 workers' compensation records of "accident" at work leading to > 3 days absence
- Used two German work hour surveys in 1992 and 1993 to estimate population exposed (the denominator) |
-Chi Square
- Relative risk |
- Relative risk for "accident" increased exponentially beyond the 9th hour at work.
- Interaction for time of day by hour at work (Chi-square = 71484, df = 264; p < 0.0001) suggests "accident" risk beyond 8th or 9th hour was greater for evening and night shifts as compared with days. |
| Johnson and Sharit 2001 |
Production workers at one manufacturing site:
- One division (n = 350, 90% male) that changed shift length was compared with other divisions (n = about 7700, 84% male)
- Age groups: > 30, 30 - 39, 40 - 49, >50
- United States |
- 8-h 3-shift rotation changes to 12-h day/night rotation
- Work h/wk not available |
- OSHA work-related injury/illness records examined over 10 years (2 y before schedule change, 8 y after change)
- Hours of Work Questionnaire measured overall health and digestive symptoms while on 8-h shifts, 11 months after change to 12-h shifts, and 8 y after change |
- Z-scores adjusted for age and gender
- Tested standardized incident/illness rate, lost time case rate, lost workday rate
- Chi Square for independence tested digestive symptoms |
- Significant increases found only in control group for injury rates, lost time case rates, lost workday rates (all p< .05).
- Digestive symptoms and overall perceived health showed improvement after changing to 12-h schedule (p < 0.001). |
| Lipscomb et al. 2002a |
1,163 working nurses randomly selected from two states:
- Age M 45
- Women 95%
- United States |
One-time questionnaire:
- Work h/day: <= 8; 9 - 11; >= 12
- Work h/wk: <=40; 41 - 49;>=50
- Work days/wk: 1 - 5; 6 - 7
- Day shift versus other
Interactions: h/shift by h/wk |
One-time Nordic Survey of Musculoskeletal Symptoms |
Logistic regression adjusted for age |
- Compared to 8-h shift, >= 12-h/ day increased risk for back disorders (OR 1.61, CI 1.05 - 2.48).
- Interactions suggested that >= 12-h/day combined with >= 40-h/week elevated risk for disorders of neck (OR 2.30, CI 1.03 - 5.11), shoulder (OR 2.48, CI 1.07 - 5.77), and back (OR 2.67, CI 1.26 - 5.66). |
| Lowden et al. 1998 |
14 shift workers, 9 day workers at a chemical plant:
- Gender age not reported for subsample
- Sweden |
8-h 3-shift backward fast rotation with M 40 h/wk changed to 12-h day/night fast rotation (2N, 5 off, 2D, 2 off, 3N) with M 36 h/wk |
Before shift change and 10 months after tested simple visual reaction time at beginning and end of shift |
- ANOVA
- Chi square
- Newman-Keuls post hoc procedures |
Simple visual reaction-time results showed no differences in performance with the change from an 8-h 3-shift rotation to a 12-h day/night rotation |
