Pre-phototherapy total serum bilirubin levels in extremely preterm infants.

BACKGROUND: Extremely preterm infants are prone to hyperbilirubinemia and its sequelae. Currently recommended thresholds for initiating phototherapy in these newborns are consensus-based (CB). METHODS: A multi-site retrospective cohort study of 642 infants born at 240/7 to 286/7 weeks' gestation, between January 2013 and June 2017, was conducted at three NICUs in Canada. Pre-phototherapy TSB percentile levels at 24 h of age were generated and contrasted with published CB thresholds. RESULTS: Among infants born 240/7 to 256/7 weeks' gestation, the differences between our TSB percentiles vs. the CB threshold of 85.0 µmol/L were 10.0 µmol/L (95% CI, 6.0-16.0) at the 75th percentile and 35.3 µmol/L (95% CI, 26.1-42.8) at the 95th percentile. Respectively, among infants born at 260/7 to 276/7 weeks, differences were 19.4 µmol/L (95% CI, 16.8-23.4) and 43.3 µmol/L (95% CI, 34.7-46.9). Born at 280/7 to 286/7 weeks' gestation, differences between our 75th and 95th TSB percentiles and the CB threshold of 103 µmol/L were 6.9 µmol/L (95% CI, 3.2-12.0) and 36.0 µmol/L (95% CI, 31.0-44.3), respectively. CONCLUSIONS: We provide statistically derived pre-phototherapy TSB levels that may clarify patterns of pre-phototherapy TSB levels in extremely preterm infants. IMPACT: We present statistically derived pre-phototherapy total serum bilirubin levels in a cohort of extremely preterm infants. Most of these preterm infants received phototherapy-some at below currently published thresholds. There are notable differences between our statistically derived pre-phototherapy TSB levels and currently published lower limit TSB thresholds for phototherapy. Our study results assist in the understanding of pre-phototherapy TSB levels in extremely preterm infants.

Mental health trajectories in undergraduate students over the first year of university: a longitudinal cohort study.

OBJECTIVE: This study examined the association between candidate psychosocial and lifestyle variables and the trajectories of clinically significant anxiety and depressive symptoms from entry to completion of first-year university. DESIGN: A longitudinal cohort study PARTICIPANTS: First-year undergraduate students METHODS: We analysed the responses of 1686 first-year undergraduate students attending Queen's University who completed electronic surveys at both the beginning and completion of their academic year. Predictors of change in positive anxiety and depressive symptom screens (based on exceeding validated symptom threshold scores) were identified using logistic regression. RESULTS: Increased university connectedness reduced the odds of emergent significant depressive and anxiety symptoms in healthy students and increased the odds of recovery in students who screened positive at the start of university. Students who screened positive for depression or anxiety at university entry were less likely to recover if they had a lifetime history of internalising disorders. Healthy students who increased their drug use over their first year had higher odds of developing significant levels of both anxiety and depressive symptoms by completion of the academic year. CONCLUSIONS: Moderate to severe levels of anxiety and depressive symptoms are common among students at entry to university and persist over the first year. University connectedness may mitigate the risk of persistent or emergent symptoms, whereas drug use appears to increase these risks. Findings have implications for university well-being initiatives.

Hour-Specific Total Serum Bilirubin Percentiles for Infants Born at 29-35 Weeks' Gestation.

INTRODUCTION: As preterm infants are susceptible to hyperbilirubinemia, they require frequent close monitoring. Prior to initiation of phototherapy, hour-specific total serum bilirubin (TSB) percentile cut-points are lacking in these infants, which led to the current study. METHODS: A multi-site retrospective cohort study of preterm infants born between January 2013 and June 2017 was completed at 3 NICUs in Ontario, Canada. A total of 2,549 infants born at 290/7-356/7 weeks' gestation contributed 6,143 pre-treatment TSB levels. Hour-specific TSB percentiles were generated using quantile regression, further described by degree of prematurity, and among those who subsequently received phototherapy. RESULTS: Among all infants, at birth, hour-specific pre-treatment, TSB percentiles were 36.1 µmol/L (95% confidence interval [CI]: 34.3-39.3) at the 40th, 52.3 µmol/L (49.4-55.1) at the 75th, and 79.5 µmol/L (72.1-89.6) at the 95th percentiles. The corresponding percentiles were 39.3 µmol/L (35.9-43.2), 55.4 µmol/L (52.1-60.2), and 87.1 µmol/L (CI 70.5-102.4) prior to initiating phototherapy and 24.4 µmol/L (20.4-28.8), 35.3 µmol/L (31.1-41.5), and 52.0 µmol/L (46.1-62.4) among those who did not receive phototherapy. Among infants born at 29-32 weeks, pre-treatment TSB percentiles were 53.9 µmol/L (49.4-61.0) and 95.5 µmol/L (77.5-105.0) at the 75th and 95th percentiles, with respective values of 48.7 µmol/L (43.0-52.3), and 74.1 µmol/L (64.8-83.2) for those born at 33-35 weeks' gestation. CONCLUSION: Hour-specific TSB percentiles, derived from a novel nomogram, may inform how bilirubin is described in preterm newborns. Further research of pre-treatment TSB levels is required before clinical consideration.

Exponential decay for binary time-varying covariates in Cox models.

Cox models are commonly used in the analysis of time to event data. One advantage of Cox models is the ability to include time-varying covariates, often a binary covariate that codes for the occurrence of an event that affects an individual subject. A common assumption in this case is that the effect of the event on the outcome of interest is constant and permanent for each subject. In this paper, we propose a modification to the Cox model to allow the influence of an event to exponentially decay over time. Methods for generating data using the inverse cumulative density function for the proposed model are developed. Likelihood ratio tests and AIC are investigated as methods for comparing the proposed model to the commonly used permanent exposure model. A simulation study is performed, and 3 different data sets are presented as examples.