Why have working hour restrictions apparently not improved patient safety?

Restrictions on hours worked by medical trainees have been in place in the United Kingdom since 1996 and across the United States since 2003. In their systematic review (doi:10.1136/bmj.d1580), Moonesinghe and colleagues concluded that these restrictions have had no negative impact on patient care and medical education; similar results were found in other reviews.1 2 3 It is reassuring that these changes do not seem to have negatively affected education, although we will not know their full impact until several years after these trainees are in independent practice. However, given that one of the fundamental principles behind these reforms was to improve patient safety,4 why have they not benefited patients⇑?

It seems self evident that a reduction in work hours should lead to improvements in patient safety and outcomes. Irrefutable evidence shows that fatigue impairs performance on standardised assessments, both in cognitive and procedural specialties.5 In the real world, however, a simple mandate of working fewer hours may not have improved …