their counterparts who work days to face divorce; for married mothers, fixed nights increase the odds by a factor of 3. Effects of resident sleep deprivation on patients The public and the medical education establishment recognize that long hours can be counter-productive, since sleep deprivation increases rates of medical errors and affects attention and working memory. Chronically sleep-deprived people also tend to strongly underestimate their degree of impairment. A study found that after 24 hours of sustained wakefulness, hand-eye coordination decreased to a level equal to the performance observed at a blood alcohol concentration of roughly 0.10%. In a meta-analysis of 959 physicians, staying awake for a continuous 24 to 30 hours decreased physicians' overall performance by nearly 1 standard deviation and clinical performance by more than 1.5 standard deviations. Competence is affected by the number of work hours, number of continuous work hours, regularity of sleep, and frequency and speed of handovers to the next shift. "Night float" seems to have particularly bad effects, due to the circadian misalignment cause by abrupt switches between day and night shifts, but is the most commonly used method of adapting to duty hour restrictions. Many studies have found performance impairment in medical residents due to sleep deprivation. The average sleep time was less for the same emergency department residents working night shifts than when working day shifts, and they took longer to intubate a mannequin and made more errors in a triage simulation when working on the night shift than the day shift. First year medical residents given an EKG arrhythmia-detection task performed significantly worse while sleep-deprived than when well-rested. Medical residents were also found to take more time and make more errors on laparoscopic procedures after one night on call. A 2004 landmark study found reducing sleep deprivation substantially reduced errors in intensive care units. The study redesigned first-year junior doctors' schedules to minimize the effects of sleep deprivation, circadian disruption, and handover problems, assigning four shifts where there had been three and allowing an hour's overlap for handovers at the ends of shifts. Each junior doctor was closely observed under both schedules. Errors were recorded (and corrected); they were then rated for severity by other doctors blinded to which treatment the errors had occurred under. Doctors and observers inevitably knew that they were part of a study. In 2015 two controlled studies of the effect of the ACGME-mandated maximum shift