Differences in medical error risk among nurses working two- and three-shift systems at teaching hospitals: a six-month prospective study.

Shift work, including night work, has been regarded as a risk factor for medical safety. However, few studies have investigated the difference in medical error risk between two- and three-shift systems. A total of 1,506 registered nurses working shifts at teaching hospitals participated in this study to evaluate the difference in medical error risk between two- and three-shift systems. After adjustment for potential confounding factors using a log Poisson generalized estimating equation model, the results showed significantly higher frequencies of perceived adverse events over 6 months in the three-shift than in the two-shift system, with estimated mean numbers of adverse events of 1.05 and 0.74, respectively. Shorter intervals after night shifts and greater frequency of night shifts in three-shift systems, which reduce the recovery time from night shift work, may be linked to increased medical errors by nurses.