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Charles A Czeisler

Publications and source records attributed to Charles A Czeisler.

At least 19 recordsLinked to original sources
PubMed2006

Extended work duration and the risk of self-reported percutaneous injuries in interns.

CONTEXT: In their first year of postgraduate training, interns commonly work shifts that are longer than 24 hours. Extended-duration work shifts are associated with increased risks of automobile crash, particularly during a commute from work. Interns may be at risk for other occupation-related injuries. OBJECTIVE: To assess the relationship between extended work duration and rates of percutaneous injuries in a diverse population of interns in the United States. DESIGN, SETTING, AND PARTICIPANTS: National prospective cohort study of 2737 of the estimated 18,447 interns in US postgraduate residency programs from July 2002 through May 2003. Each month, comprehensive Web-based surveys that asked about work schedules and the occurrence of percutaneous injuries in the previous month were sent to all participants. Case-crossover within-subjects analyses were performed. MAIN OUTCOME MEASURES: Comparisons of rates of percutaneous injuries during day work (6:30 am to 5:30 pm) after working overnight (extended work) vs day work that was not preceded by working overnight (nonextended work). We also compared injuries during the nighttime (11:30 pm to 7:30 am) vs the daytime (7:30 am to 3:30 pm). RESULTS: From a total of 17,003 monthly surveys, 498 percutaneous injuries were reported (0.029/intern-month). In 448 injuries, at least 1 contributing factor was reported. Lapse in concentration and fatigue were the 2 most commonly reported contributing factors (64% and 31% of injuries, respectively). Percutaneous injuries were more frequent during extended work compared with nonextended work (1.31/1000 opportunities vs 0.76/1000 opportunities, respectively; odds ratio [OR], 1.61; 95% confidence interval [CI], 1.46-1.78). Extended work injuries occurred after a mean of 29.1 consecutive work hours; nonextended work injuries occurred after a mean of 6.1 consecutive work hours. Injuries were more frequent during the nighttime than during the daytime (1.48/1000 opportunities vs 0.70/1000 opportunities, respectively; OR, 2.04; 95% CI, 1.98-2.11). CONCLUSION: Extended work duration and night work were associated with an increased risk of percutaneous injuries in this study population of physicians during their first year of clinical training.

Accidents, Occupational↗
PubMed2006

Interns' compliance with accreditation council for graduate medical education work-hour limits.

CONTEXT: Sleep deprivation is associated with increased risk of serious medical errors and motor vehicle crashes among interns. The Accreditation Council for Graduate Medical Education (ACGME) introduced duty-hour standards in 2003 to reduce work hours. OBJECTIVE: To estimate compliance with the ACGME duty-hour standards among interns. DESIGN, SETTING, AND PARTICIPANTS: National prospective cohort study with monthly Web-based survey assessment of intern work and sleep hours using a validated instrument, conducted preimplementation (July 2002 through May 2003) and postimplementation (July 2003 through May 2004) of ACGME standards. Participants were 4015 of the approximately 37 253 interns in US residency programs in all specialties during this time; they completed 29 477 reports of their work and sleep hours. MAIN OUTCOME MEASURE: Overall and monthly rates of compliance with the ACGME standards. RESULTS: Postimplementation, 1068 (83.6%; 95% confidence interval [CI], 81.4%-85.5%) of 1278 of interns reported work hours in violation of the standards during 1 or more months. Working shifts greater than 30 consecutive hours was reported by 67.4% (95% CI, 64.8%-70.0%). Averaged over 4 weeks, 43.0% (95% CI, 40.3%-45.7%) reported working more than 80 hours weekly, and 43.7% (95% CI, 41.0%-46.5%) reported not having 1 day in 7 off work duties. Violations were reported during 3765 (44.0%; 95% CI, 43.0%-45.1%) of the 8553 intern-months assessed postimplementation (including vacation and ambulatory rotations), and during 2660 (61.5%; 95% CI, 60.0%-62.9%) of 4327 intern-months during which interns worked exclusively in inpatient settings. Postimplementation, 29.0% (95% CI, 28.7%-29.7%) of reported work weeks were more than 80 hours per week, 12.1% (95% CI, 11.8%-12.6%) were 90 or more hours per week, and 3.9% (95% CI, 3.7%-4.2%) were 100 or more hours per week. Comparing preimplementation to postimplementation responses, reported mean work duration decreased 5.8% from 70.7 (95% CI, 70.5-70.9) hours to 66.6 (95% CI, 66.3-66.9) hours per week (P<.001), and reported mean sleep duration increased 6.1% (22 minutes) from 5.91 (95% CI, 5.88-5.94) hours to 6.27 (95% CI, 6.23-6.31) hours per night (P<.001). However, reported mean sleep during extended shifts decreased 4.5%, from 2.69 (95% CI, 2.66-2.73) hours to 2.57 (95% CI, 2.52-2.62) hours (P<.001). CONCLUSION: In the first year following implementation of the ACGME duty-hour standards, interns commonly reported noncompliance with these requirements.

Adult↗
PubMed2006

Decreased sensitivity to phase-delaying effects of moderate intensity light in older subjects.

Aging is associated with a change in the relationship between the timing of sleep and circadian rhythms, such that the rhythms occur later with respect to sleep than in younger adults. To investigate whether a difference in the phase-delaying response to evening light contributes to this, we conducted a 9-day inpatient study in 10 healthy older (> or =65 y.o.) subjects. We assessed circadian phase in a constant routine, exposed each subject to a 6.5h broad-spectrum light stimulus beginning in the early biological night, and reassessed circadian phase. The stimuli spanned a range from very dim (approximately 2 lx) to very bright (approximately 8000 lx) indoor light. We found a significant dose-response relationship between illuminance and the phase shift of the melatonin rhythm, with evidence that sensitivity, but not the maximal response to light, differed from that of younger adults. These findings suggest an age-related reduction in the phase-delaying response to moderate light levels. However, our findings alone do not explain the altered phase relationship between sleep and circadian rhythms associated with aging.

Aged↗
PubMed2006

Recovery from medical errors: the critical care nursing safety net.

BACKGROUND: Safety initiatives have primarily focused on physicians despite the fact that nurses provide the majority of direct inpatient care. Patient surveillance and preventing errors from harming patients represent essential nursing responsibilities but have received relatively little study. METHODS: The study was conducted between July 2003 and July 2004 in a 10-bed academic coronary care unit. Direct observation of nursing care and solicited and institutional incident reports were used to find potential incidents. Two physician reviewers rated incidents as to the presence, preventability, and potential severity of harm of errors and associated factors. RESULTS: Overall data were collected for 147 days, including 150 hours of direct observation. One hundred forty-two recovered medical errors were found, including 61% (86/142) during direct observations. Most errors (69%; 98/142) were intercepted before reaching the patients. Errors that reached patients included 13% that were mitigated before resulting in harm and 18% that were ameliorated before more severe harm could occur. DISCUSSION: Protecting patients from the potentially dangerous consequences of medical errors is one of the many ways critical care nurses improve patient safety. Interventions designed to increase the ability of nurses to recover and promptly report errors have the potential to improve patient outcomes.

Academic Medical Centers↗
PubMed2006

Diurnal variation in CSF orexin-A in healthy male subjects.

STUDY OBJECTIVE: Orexin-A is hypothesized to promote wakefulness, and we examined whether cerebrospinal fluid (CSF) orexin-A levels are higher during the waking period in man. DESIGN: Within-subjects, repeated-measures design with balanced ordering of sampling at approximately 5 AM and 5 PM. PARTICIPANTS: Eight healthy young males. MESUREMENTS: CSF orexin-A levels and standard polysomnography. RESULTS: Orexin-A levels during the sleep period were 4% higher than during the waking period (314.9 pg/ml versus 302.8 pg/ml, p < 0.03). Sleep period orexin-A levels were negatively correlated with REM sleep as a percentage of total sleep time (p < 0.05). The day and night levels of orexin-A were strongly correlated within subjects (r = 0.97; p < 0.0001) even though the samples were collected 1-2 weeks apart. CONCLUSIONS: Orexin-A levels in lumbar CSF are slightly higher at 5 AM than at 5 PM. Because orexin release is thought to be highest during the waking period, this observation was unexpected and may reflect a long delay between the release of orexin and its appearance in lumbar CSF. Orexin-A levels vary moderately between subjects, but are quite consistent within the same subject. Thus, for the diagnostic evaluation of narcolepsy, the time of CSF collection should have little impact.

Adult↗
PubMed2006

Sleep-facilitating effect of exogenous melatonin in healthy young men and women is circadian-phase dependent.

STUDY OBJECTIVES: To investigate the effects of a physiologic and a pharmacologic dose of exogenous melatonin on sleep latency and sleep efficiency in sleep episodes initiated across a full range of circadian phases. DESIGN: Double-blind placebo-controlled parallel-group design in a 27-day forced desynchrony paradigm with a 20-hour scheduled sleep-wake cycle. SETTING: Private suite of a general clinical research center, in the absence of time-of-day information. SUBJECTS: Thirty-six healthy, 18- to 30-year-old, men (n = 21) and women (n = 15). INTERVENTIONS: Oral melatonin (0.3 mg or 5.0 mg) or identical-appearing placebo was administered 30 minutes prior to each 6.67-hour sleep episode during forced desynchrony. MEASUREMENTS AND RESULTS: Both doses of melatonin improved polysomnographically determined sleep efficiency from 77% in the placebo group to 83% for sleep episodes occurring during circadian phases when endogenous melatonin was absent. However, this remained below the average sleep efficiency of 88% observed during sleep episodes scheduled during the circadian night, when endogenous melatonin was present. Melatonin did not significantly affect sleep initiation or core body temperature. Melatonin appeared to maintain efficacy across the study and did not significantly affect percentages of slow-wave sleep or rapid eye movement sleep. CONCLUSIONS: Exogenous melatonin administration possesses circadian-phase-dependent hypnotic properties, allowing for improved consolidation of sleep that occurs out of phase with endogenous melatonin secretion during the circadian night. The results support the hypothesis that both exogenous and endogenous melatonin attenuate the wake-promoting drive from the circadian system.

Administration, Oral↗
PubMed2006

When policy meets physiology: the challenge of reducing resident work hours.

Considerable controversy exists regarding optimal work hours for physicians and surgeons in training. In a series of studies, we assessed the effect of extended work hours on resident sleep and health as well as patient safety. In a validated nationwide survey, we found that residents who had worked 24 hours or longer were 2.3 times more likely to have a motor vehicle crash following that shift than when they worked < 24 hours, and that the monthly risk of a crash increased by 16.2% after each extended duration shift. We also found in a randomized trial that interns working a traditional on-call schedule slept 5.8 hours less per week, had twice as many attentional failures on duty overnight, and made 36% more serious medical errors and nearly six times more serious diagnostic errors than when working on a schedule that limited continuous duty to 16 hours. While numerous opinions have been published opposing reductions in extended work hours due to concerns regarding continuity of patient care, reduced educational opportunities, and traditionally-defined professionalism, there are remarkably few objective data in support of continuing to schedule medical trainees to work shifts > 24 hours. An evidence-based approach is needed to minimize the well-documented risk that current work hour practices confer on resident health and patient safety while optimizing education and continuity of care.

Accidents, Traffic↗
PubMed2006

Sleep and wakefulness out of phase with internal biological time impairs learning in humans.

Sleep-wake homeostatic and internal circadian timedependent brain processes interact to regulate human brain function so that alert wakefulness is promoted during the daytime and consolidated sleep is promoted at nighttime. The consequence of chronically altering the normal relationship between these processes for human brain function is largely unknown. We tested cognitive and vigilance performance while subjects lived in the laboratory for over a month. The subjects lived on either 24.0- or 24.6-hr day lengths. Half of the subjects tested maintained a normal relationship between sleep-wakefulness and internal circadian time (synchronized group), whereas the other half did not (nonsynchronized group). Levels of the sleep-promoting hormone melatonin were high during scheduled sleep in the synchronized group, whereas melatonin levels were high during scheduled wakefulness in the nonsynchronized group. Failure to adapt to the scheduled day length was dependent upon individual differences in intrinsic circadian period. Total sleep time was reduced, sleep latency and Rapid Eye Movement (REM) latency were shortened, and wakefulness after sleep onset was increased in the nonsynchronized group. Cognitive performance improved (i.e., learning) in the synchronized group, whereas learning was significantly impaired in the nonsynchronized group. Attention progressively declined in both groups, suggesting that 8 hr of scheduled sleep per night is insufficient to maintain brain vigilance even when sleep occurs at an appropriate biological time. Our results establish that proper alignment between sleep-wakefulness and internal circadian time is crucial for enhancement of cognitive performance. In addition, our results demonstrate that exposure to dim light (approximately 25 lx) is sufficient to expand the range of entrainment in humans.

Adult↗
PubMed2006

Impact of extended-duration shifts on medical errors, adverse events, and attentional failures.

BACKGROUND: A recent randomized controlled trial in critical-care units revealed that the elimination of extended-duration work shifts (> or =24 h) reduces the rates of significant medical errors and polysomnographically recorded attentional failures. This raised the concern that the extended-duration shifts commonly worked by interns may contribute to the risk of medical errors being made, and perhaps to the risk of adverse events more generally. Our current study assessed whether extended-duration shifts worked by interns are associated with significant medical errors, adverse events, and attentional failures in a diverse population of interns across the United States. METHODS AND FINDINGS: We conducted a Web-based survey, across the United States, in which 2,737 residents in their first postgraduate year (interns) completed 17,003 monthly reports. The association between the number of extended-duration shifts worked in the month and the reporting of significant medical errors, preventable adverse events, and attentional failures was assessed using a case-crossover analysis in which each intern acted as his/her own control. Compared to months in which no extended-duration shifts were worked, during months in which between one and four extended-duration shifts and five or more extended-duration shifts were worked, the odds ratios of reporting at least one fatigue-related significant medical error were 3.5 (95% confidence interval [CI], 3.3-3.7) and 7.5 (95% CI, 7.2-7.8), respectively. The respective odds ratios for fatigue-related preventable adverse events, 8.7 (95% CI, 3.4-22) and 7.0 (95% CI, 4.3-11), were also increased. Interns working five or more extended-duration shifts per month reported more attentional failures during lectures, rounds, and clinical activities, including surgery and reported 300% more fatigue-related preventable adverse events resulting in a fatality. CONCLUSIONS: In our survey, extended-duration work shifts were associated with an increased risk of significant medical errors, adverse events, and attentional failures in interns across the United States. These results have important public policy implications for postgraduate medical education.

Adult↗
PubMed2006

Short-wavelength sensitivity for the direct effects of light on alertness, vigilance, and the waking electroencephalogram in humans.

STUDY OBJECTIVES: To assess the wavelength-dependent sensitivity of the acute effects of ocular light exposure on alertness, performance, waking electroencephalogram (EEG), and cortisol. DESIGN: A between-subjects design was employed to compare the effects of exposure to 460-nm or 555-nm light for 6.5 hours during the biological night. SETTING: Intensive Physiological Monitoring Unit, Brigham and Women's Hospital, Boston, MA. PATIENTS AND PARTICIPANTS: Sixteen healthy adults (8 women; mean age +/- SD = 23.3 +/- 2.4 years). INTERVENTIONS: Subjects were exposed to equal photon densities (2.8 x 10(13) photons x cm(-2) x s(-1)) of either 460-nm (n = 8) or 555-nm (n = 8) monochromatic light for 6.5 hours, 15 minutes after mydriasis. MEASUREMENTS AND RESULTS: Subjects underwent continuous EEG/electrooculogram recordings and completed a performance battery every 30 to 60 minutes. As compared with those exposed to 555-nm light, subjects exposed to 460-nm light had significantly lower subjective sleepiness ratings, decreased auditory reaction time, fewer attentional failures, decreased EEG power density in the delta-theta range (0.5-5.5 Hz), and increased EEG power density in the high-alpha range (9.5-10.5 Hz). Light had no direct effect on cortisol. CONCLUSIONS: Short-wavelength sensitivity to the acute alerting effects of light indicates that the visual photopic system is not the primary photoreceptor system mediating these responses to light. The frequency-specific changes in the waking EEG indicate that short-wavelength light is a powerful agent that immediately attenuates the negative effects of both homeostatic sleep pressure and the circadian drive for sleep on alertness, performance, and the ability to sustain attention.

Adult↗
PubMed2006

Sleep deficit: the performance killer. A conversation with Harvard Medical School Professor Charles A. Czeisler.

Companies today glorify the executive who logs 100-hour workweeks, the road warrior who lives out of a suitcase in multiple time zones, and the negotiator who takes a red-eye to make an 8 A.M. meeting. But to Dr. Charles A. Czeisler, the Baldino Professor of Sleep Medicine at Harvard Medical School, this kind of corporate behavior is the antithesis of high performance. In fact, he says, it endangers employees and puts their companies at risk. In this interview, Czeisler describes four neurobiological functions that affect sleep duration and quality as well as individual performance. When these functions fall out of alignment because of sleep deprivation, people operate at a far lower level of performance than they would if they were well rested. Czeisler goes on to observe that corporations have all kinds of policies designed to protect employees- rules against smoking, sexual harassment, and so on-but they push people to the brink of self-destruction by expecting them to work too hard, too long, and with too little sleep. The negative effects on cognitive performance, Czeisler says, can be similar to those that occur after drinking too much alcohol: "We now know that 24 hours without sleep or a week of sleeping four or five hours a night induces an impairment equivalent to a blood alcohol level of .1%. We would never say, 'This person is a great worker! He's drunk all the time!' yet we continue to celebrate people who sacrifice sleep for work." Czeisler recommends that companies institute corporate sleep policies that discourage scheduled work beyond 16 consecutive hours as well as working or driving immediately after late-night or overnight flights. A sidebar to this article summarizes the latest developments in sleep research.

Administrative Personnel↗
PubMed2005

Scheduling of sleep/darkness affects the circadian phase of night shift workers.

Shift work results in a misalignment between circadian timing and the sleep/wake schedule, leading to irregular and poor quality sleep. Inconsistent input from the daily light cycle further interferes with circadian entrainment. It has been hypothesized that scheduling the sleep/dark cycle on the night shift could aid in promoting adaptation to night shift work by facilitating appropriate phase shifts. In a simulated shift-work study, we compared the ability of two sleep/dark schedules to shift circadian phase. Our results indicate that scheduled sleep/darkness can aid in adaptation to night shift work by inducing both advance and delay phase shifts, depending on the timing of the sleep schedule, although the size of the phase shifts are not sufficient to produce complete adaptation to the night shift. These results have applications to night shift workers, particularly in occupations in which alterations in the timing of light exposure cannot be achieved during working hours.

Adaptation, Physiological↗
PubMed2005

Modafinil for excessive sleepiness associated with shift-work sleep disorder.

BACKGROUND: Patients with shift-work sleep disorder chronically have excessive sleepiness during night work and insomnia when attempting to sleep during the day. We evaluated the use of modafinil for treating sleepiness in patients with this disorder. METHODS: In a three-month, double-blind trial, we randomly assigned 209 patients with shift-work sleep disorder to receive either 200 mg of modafinil or placebo before the start of each shift. Assessments were performed with the use of the nighttime Multiple Sleep Latency Test, the Clinical Global Impression of Change, the Psychomotor Vigilance Test, diaries of patients, and daytime polysomnography. After randomization, we conducted monthly assessments. RESULTS: Treatment with modafinil, as compared with placebo, resulted in a modest improvement from baseline in mean (+/-SEM) nighttime sleep latency (the interval between the time a person attempts to fall asleep and the onset of sleep) (1.7+/-0.4 vs. 0.3+/-0.3 minutes, respectively; P=0.002), and more patients had improvement in their clinical symptoms (74 percent vs. 36 percent, respectively; P<0.001). Patients who were receiving modafinil also had a reduction in the frequency and duration of lapses of attention during nighttime testing of their performance on the Psychomotor Vigilance Test (change from baseline, a reduction in lapse frequency of 2.6 vs. an increase of 3.8, respectively; P<0.001), and proportionally fewer patients reported having had accidents or near accidents while commuting home (29 percent vs. 54 percent, respectively; P<0.001). Despite these benefits, patients treated with modafinil continued to have excessive sleepiness and impaired performance at night. Modafinil did not adversely affect daytime sleep as compared with placebo. Headache was the most common adverse event. CONCLUSIONS: Treatment with 200 mg of modafinil reduced the extreme sleepiness that we observed in patients with shift-work sleep disorder and resulted in a small but significant improvement in performance as compared with placebo. However, the residual sleepiness that was observed in the treated patients underscores the need for the development of interventions that are even more effective.

Adult↗
PubMed2005

Temporal dynamics of late-night photic stimulation of the human circadian timing system.

The light-dark cycle is the primary synchronizing factor that keeps the internal circadian pacemaker appropriately aligned with the environmental 24-h day. Although it is known that ocular light exposure can effectively shift the human circadian pacemaker and do so in an intensity-dependent manner, the curve that describes the relationship between light intensity and pacemaker response has not been fully characterized for light exposure in the late biological night. We exposed subjects to 3 consecutive days of 5 h of experimental light, centered 1.5 h after the timing of the fitted minimum of core body temperature, and show that such light can phase advance shift the human circadian pacemaker in an intensity-dependent manner, with a logistic model best describing the relationship between light intensity and phase shift. A similar sigmoidal relationship is also observed between light intensity and the suppression of plasma melatonin concentrations that occurs during the experimental light exposure. As with a simpler, 1-day light exposure during the early biological night, our data indicate that the human circadian pacemaker is highly sensitive even to typical room light intensities during the late biological night, with approximately 100 lux evoking half of the effects observed with light 10 times as bright.

Adult↗
PubMed2005

Extended work shifts and the risk of motor vehicle crashes among interns.

BACKGROUND: Long work hours and work shifts of an extended duration (> or =24 hours) remain a hallmark of medical education in the United States. Yet their effect on health and safety has not been evaluated with the use of validated measures. METHODS: We conducted a prospective nationwide, Web-based survey in which 2737 residents in their first postgraduate year (interns) completed 17,003 monthly reports that provided detailed information about work hours, work shifts of an extended duration, documented motor vehicle crashes, near-miss incidents, and incidents involving involuntary sleeping. RESULTS: The odds ratios for reporting a motor vehicle crash and for reporting a near-miss incident after an extended work shift, as compared with a shift that was not of extended duration, were 2.3 (95 percent confidence interval, 1.6 to 3.3) and 5.9 (95 percent confidence interval, 5.4 to 6.3), respectively. In a prospective analysis, every extended work shift that was scheduled in a month increased the monthly risk of a motor vehicle crash by 9.1 percent (95 percent confidence interval, 3.4 to 14.7 percent) and increased the monthly risk of a crash during the commute from work by 16.2 percent (95 percent confidence interval, 7.8 to 24.7 percent). In months in which interns worked five or more extended shifts, the risk that they would fall asleep while driving or while stopped in traffic was significantly increased (odds ratios, 2.39 [95 percent confidence interval, 2.31 to 2.46] and 3.69 [95 percent confidence interval, 3.60 to 3.77], respectively). CONCLUSIONS: Extended-duration work shifts, which are currently sanctioned by the Accreditation Council for Graduate Medical Education, pose safety hazards for interns. These results have implications for medical residency programs, which routinely schedule physicians to work more than 24 consecutive hours.

Accidents, Traffic↗