Publications

BACKGROUND: The effects on patient safety of eliminating extended-duration work shifts for resident physicians remain controversial.

METHODS: We conducted a multicenter, cluster-randomized, crossover trial comparing two schedules for pediatric resident physicians during their intensive care unit (ICU) rotations: extended-duration work schedules that included shifts of 24 hours or more (control schedules) and schedules that eliminated extended shifts and cycled resident physicians through day and night shifts of 16 hours or less (intervention schedules). The primary outcome was serious medical errors made by resident physicians, assessed by intensive surveillance, including direct observation and chart review.

RESULTS: The characteristics of ICU patients during the two work schedules were similar, but resident physician workload, described as the mean (±SD) number of ICU patients per resident physician, was higher during the intervention schedules than during the control schedules (8.8±2.8 vs. 6.7±2.2). Resident physicians made more serious errors during the intervention schedules than during the control schedules (97.1 vs. 79.0 per 1000 patient-days; relative risk, 1.53; 95% confidence interval [CI], 1.37 to 1.72; P<0.001). The number of serious errors unitwide were likewise higher during the intervention schedules (181.3 vs. 131.5 per 1000 patient-days; relative risk, 1.56; 95% CI, 1.43 to 1.71). There was wide variability among sites, however; errors were lower during intervention schedules than during control schedules at one site, rates were similar during the two schedules at two sites, and rates were higher during intervention schedules than during control schedules at three sites. In a secondary analysis that was adjusted for the number of patients per resident physician as a potential confounder, intervention schedules were no longer associated with an increase in errors.

CONCLUSIONS: Contrary to our hypothesis, resident physicians who were randomly assigned to schedules that eliminated extended shifts made more serious errors than resident physicians assigned to schedules with extended shifts, although the effect varied by site. The number of ICU patients cared for by each resident physician was higher during schedules that eliminated extended shifts. (Funded by the National Heart, Lung, and Blood Institute; ROSTERS ClinicalTrials.gov number, NCT02134847.).

The North American Menopause Society held the 2019 Pre-Meeting Symposium on September 25, 2019, in Chicago, Illinois, to review the current state of the science related to the physiology of the perimenopause and to address management of the most prevalent and pressing clinical issues. The perimenopause, as defined by the Stages of Reproductive Aging Workshop + 10, encompasses the menopause transition as well as the first year following menopause, the final menstrual period. This phase in the continuum of women's reproductive lives had been one of the least well understood. Fortunately, contributions from a number of prospective, longitudinal, decades-long studies have provided a better understanding of the perimenopause, whereas posing important new questions related to symptom interaction and linkages between symptoms and long-term health. There is now added clarity to distinguish the effects of reproductive hormonal changes from aging. The variation in symptoms, including vasomotor symptoms, among women over time including differences in experiences by ethnicity and race, provides paradigm shifts in clinical perspective. Refinements in understanding the character, timing, and potential predictive markers for menstrual cycles during the transition have emerged. From the perspective of myriad clinical management challenges, significant progress in recommendations for evaluation and therapeutic approaches has been achieved. Finally, recognizing the menopause transition as an opportunity to initiate positive lifestyle changes to enhance future health was emphasized.

OBJECTIVE: Dysregulated responses to experimental stress paradigms may indicate exposure to chronic stress. Vasomotor symptoms (VMS) are linked with diminished quality of life and psychological stress, but induced stress responsivity has received limited investigation. We examined whether women with and without VMS differ in their evoked hypothalamic-pituitary-adrenal axis, subjective, hemodynamic, and thermal stress responses.

METHODS: A total of 37 midlife women (27 VMS+; 10 VMS-) completed 2 experimental stress paradigms: (1) Montreal Imaging Stress Task (MIST; computerized social-evaluative stressor) and (2) Quantitative Sensory Testing (QST; thermal stress task). Responses on a five-domain (range 0-50) Visual Analog Scale, salivary cortisol (hypothalamic-pituitary-adrenal axis), and hemodynamic indices (blood pressure, heart rate) were measured before and after each task to compare within-person change between groups. Thermal sensitivity was assessed on the QST.

RESULTS: On the MIST, the VMS+ group showed a smaller cortisol release (0.01 vs 0.07 μg/dL; P = 0.046; corresponding to 54% vs 83% increases), and subjective stress response (21.2- vs 31.1-point Visual Analog Scale increase, P = 0.05; corresponding to 2427% vs 2863% increases) but no hemodynamic difference, compared to the VMS- group. The QST did not provoke stress responses via cortisol release or subjective report, but the VMS+ group tended to perceive heat at a higher temperature (38.5°C vs 36.4°C, P = 0.08).

CONCLUSIONS: Women with VMS exhibited both diminished cortisol and subjective stress responses to the MIST, and reduced thermal sensitivity on QST compared to women without VMS. Dysregulated stress responsivity provides preliminary evidence suggesting that VMS may represent a chronic stress condition.

OBJECTIVES: The association between sleep and adiposity (indexed by body mass index or waist-to-hip ratio) has typically been evaluated using a single dimension of self-reported sleep. However, other dimensions and behavioral measures of sleep may also be associated with adiposity. This study evaluated whether multidimensional sleep health calculated from actigraphy and self-report was longitudinally associated with adiposity in a sample of midlife women who have a high prevalence of sleep disturbances and adiposity.

DESIGN: Longitudinal study with 11-14 years of follow-up time between the sleep health assessment and body mass index / waist-to-hip ratio measurements.

PARTICIPANTS: Two hundred and twenty-one midlife women enrolled in the Study of Women's Health Across the Nation Sleep Study.

MEASUREMENTS: Multidimensional sleep health was quantified using actigraphy (M[SD] = 29.1[7.2] nights) measures of sleep efficiency, midpoint, duration, regularity, and self-report measures of alertness and satisfaction. Each component was dichotomized and summed; higher values indicated better sleep health. Height, body weight, and waist and hip circumference were measured at the sleep study and at follow-up. Linear regression models were used to assess associations between sleep health and adiposity, adjusting for demographic and menopausal covariates.

RESULTS: There was no substantial within-person change in adiposity over time. Better sleep health was cross-sectionally and longitudinally associated with lower adiposity in unadjusted, but not in adjusted, models. Individual sleep health components were not associated with adiposity after adjustment.

CONCLUSION: We did not observe cross-sectional or longitudinal associations between multidimensional sleep health and adiposity. The sleep-adiposity link may be weaker in midlife adults than in other age groups.

OBJECTIVE: To identify groups of women who share levels and patterns of change in follicle-stimulating hormone (FSH), self-reported sleep maintenance problems, and frequent vasomotor symptoms (VMS) up to 10 years before and after their final menstrual period and to evaluate their premenopausal characteristics.

METHOD: Group-based multi-trajectory modeling grouped 1,407 women from the Study of Women's Health Across the Nation who had an observed natural menopause and did not use hormone therapy, based on repeated measures of FSH, sleep maintenance problems, and frequent VMS relative to final menstrual period. Multivariable analyses assessed race/ethnicity, body mass index, smoking, and depressive symptoms as predictors of group membership.

RESULTS: Women formed five distinct groups: (1) low symptoms (low VMS/sleep problems)/high FSH rise (N = 552; 39.2%); (2) moderate VMS and sleep problems/low FSH rise (N = 169; 12.0%); (3) dominant sleep problems (lower VMS/high sleep problems)/high FSH rise (N = 203; 14.4%); (4) dominant VMS (high VMS/lower sleep problems)/high FSH rise (N = 297; 21.1%)); and (5) high symptoms (high VMS/high sleep problems)/intermediate FSH rise (N = 186; 13.2%)). Multivariate analyses showed that race/ethnicity, premenopausal body mass index and depressive symptoms, and increasing depressive symptoms during the early phase of the transition predicted group membership.

CONCLUSIONS: Women can be classified based on shared levels and patterns of FSH, sleep maintenance problems, and frequent VMS across the menopause transition. Either VMS or sleep maintenance problems can be dominant in the face of high FSH. Experiencing one menopause-related symptom or hormone profile does not automatically imply that another is also being experienced.

We explored the predictive value of a neurobehavioral performance assessment under rested baseline conditions (evaluated at 8 hours awake following 8 hours of sleep) on neurobehavioral response to moderate sleep loss (evaluated at 20 hours awake two days later) in 151 healthy young participants (18-30 years). We defined each participant's response-to-sleep-loss phenotype based on the number of attentional failures on a 10-min visual psychomotor vigilance task taken at 20 hours awake (resilient: less than 6 attentional failures, n = 26 participants; non-resilient: 6 or more attentional failures, n = 125 participants). We observed that 97% of rested participants with 2 or more attentional failures (n = 73 of 151) and 100% of rested participants with 3 or more attentional failures (n = 57 of 151) were non-resilient after moderate sleep loss. Our approach can accurately identify a significant proportion of individuals who are at high risk for neurobehavioral performance impairment from staying up late with a single neurobehavioral performance assessment conducted during rested conditions. Additional methods are needed to predict the future performance of individuals who are not identified as high risk during baseline.

CONTEXT: Studies suggest that female reproductive hormones are under circadian regulation, although methodological differences have led to inconsistent findings.

OBJECTIVE: To determine whether circulating levels of reproductive hormones exhibit circadian rhythms.

DESIGN: Blood samples were collected across ∼90 consecutive hours, including 2 baseline days under a standard sleep-wake schedule and ∼50 hours of extended wake under constant routine (CR) conditions.

SETTING: Intensive Physiological Monitoring Unit, Brigham and Women's Hospital.

PARTICIPANTS: Seventeen healthy premenopausal women (22.8 ± 2.6 years; nine follicular; eight luteal).

INTERVENTIONS: Fifty-hour CR.

MAIN OUTCOME MEASURES: Plasma estradiol (E2), progesterone (P4), LH, FSH, SHBG, melatonin, and core body temperature.

RESULTS: All hormones exhibited significant 24-hour rhythms under both standard sleep-wake and CR conditions during the follicular phase (P < 0.05). In contrast, only FSH and SHBG were significantly rhythmic during the luteal phase. Rhythm acrophases and amplitudes were similar between standard sleep-wake and CR conditions. The acrophase occurred in the morning for P4; in the afternoon for FSH, LH, and SHBG; and during the night for E2.

CONCLUSIONS: Our results confirm previous reports of ∼24-hour rhythms in many female reproductive hormones in humans under ambulatory conditions but demonstrate that these hormones are under endogenous circadian regulation, defined as persisting in the absence of external time cues. These results may have important implications for the effects of circadian disruption on reproductive function.

We studied the dynamics of melatonin suppression and changes in cortisol levels in humans in response to light exposure at night using high-frequency blood sampling. Twenty-one young healthy participants were randomized to receive either intermittent bright ( 9,500 lux) light (IBL), continuous bright light (CBL) or continuous dim ( 1 lux) light (VDL) for 6.5 h during the biological night (n = 7 per condition). Melatonin suppression occurred rapidly within the first 5 min and continued until the end of each IBL stimuli (t1/2 =  13 min). Melatonin recovery occurred more slowly between IBL stimuli (half-maximal recovery rate of  46 min). Mean melatonin suppression ( 40%) and recovery ( 50%) were similar across IBL stimuli. Suppression dynamics under CBL were also rapid (t1/2 =  18 min), with no recovery until the light exposure ended. There was a significant linear increase of cortisol levels between the start and end of each IBL stimulus. Under CBL conditions cortisol showed trimodal changes with an initial linear activating phase, followed by an exponential inhibitory phase, and a final exponential recovery phase. These results show that light exposure at night affects circadian driven hormones differently and that outcomes are influenced by the duration and pattern of light exposure.

Although evidence exists for a daily rhythm in bone metabolism, the contribution of factors such as melatonin levels, the light-dark cycle, and the sleep-wake cycle is difficult to differentiate given their highly correlated time courses. To examine these influences on bone resorption, we collected 48-h sequential urine samples under both ambulatory (8-h sleep:16-h wake) and constant routine (CR) (constant wake, posture, nutrition and dim light) conditions from 20 healthy premenopausal women. Urinary 6-sulphatoxymelatonin (aMT6s; ng/h) and the bone resorption marker amino-terminal cross-linked collagen I telopeptide (NTx; bone collagen equivalents nM/h) were assayed and fit by cosinor models to determine significant 24-h rhythms and acrophase. Most participants had significant 24-h aMT6s rhythms during both ambulatory and CR conditions (95 and 85%, respectively), but fewer had significant 24-h NTx rhythms (70 and 70%, respectively). Among individuals with significant rhythms, mean (± SD) aMT6s acrophase times were 3:57 ± 1:50 and 3:43 ± 1:25 h under ambulatory and CR conditions, respectively, and 23:44 ± 5:55 and 3:06 ± 5:15 h, respectively, for NTx. Mean 24-h levels of both aMT6s and NTx were significantly higher during CR compared with ambulatory conditions (p < 0.0001 and p = 0.03, respectively). Menstrual phase (follicular versus luteal) had no impact on aMT6s or NTx timing or 24-h levels. This study confirms an endogenous circadian rhythm in NTx with a night-time peak when measured under CR conditions, but also confirms that environmental factors such as the sleep-wake or light-dark cycles, posture or meal timing affects overall concentrations and peak timing under ambulatory conditions, the significance of which remains unclear.