Estimating the impact of bias in causal epidemiological studies: the case of health outcomes following assisted reproduction.

Researchers interested in causal questions must deal with two sources of error: random error (random deviation from the true mean value of a distribution), and bias (systematic deviance from the true mean value due to extraneous factors). For some causal questions, randomization is not feasible, and observational studies are necessary. Bias poses a substantial threat to the validity of observational research and can have important consequences for health policy developed from the findings. The current piece describes bias and its sources, outlines proposed methods to estimate its impacts in an observational study, and demonstrates how these methods may be used to inform debate on the causal relationship between medically assisted reproduction (MAR) and health outcomes, using cancer as an example. In doing so, we aim to enlighten researchers who work with observational data, especially regarding the health effects of MAR and infertility, on the pitfalls of bias, and how to address them. We hope that, in combination with the provided example, we can convince readers that estimating the impact of bias in causal epidemiologic research is not only important but necessary to inform the development of robust health policy and clinical practice recommendations.

Risk factors for dementia and self-harm: A linkage study.

INTRODUCTION: People living with dementia experience poor mental health and high rates of self-harm. We investigated risk factors for self-harm in people aged > 40 years living with dementia and risk factors for dementia after self-harm. METHODS: Using linked hospital data from New South Wales, Australia, we defined a dementia cohort (n = 154,811) and a self-harm cohort (n = 28,972). Using survival analyses, we investigated predictors of self-harm for the dementia cohort, and predictors of dementia for the self-harm cohort. RESULTS: We found self-harm or dementia diagnoses occurred most often within 24 months of a dementia diagnosis or initial self-harm presentation, respectively. Men living with dementia, and people with complex psychiatric profiles, had the greatest risk of self-harm. Men who had self-harmed had the greatest risk of dementia diagnoses. DISCUSSION: Men and people with complex psychiatric profiles and dementia may particularly benefit from post-diagnosis mental and behavioral support to reduce risk of self-harm.

Hospital service utilisation of people previously hospitalised with different subtypes of psychotic disorder: A record linkage study.

OBJECTIVE: Little research has examined the physical and mental comorbidities, and health service use patterns, of people diagnosed with psychotic disorder subtypes other than schizophrenia spectrum disorders. This study aims to examine the physical and mental comorbidities, and subsequent hospital service use patterns, of individuals previously hospitalised with various psychotic disorder subtypes using linked health service data. METHODS: We included individuals hospitalised with a psychotic disorder in New South Wales, Australia, between 1 July 2002 and 31 December 2014 (N = 63,110). We examined the demographic profile of the cohort and rates of subsequent acute hospital care and ambulatory mental health service use. We compared the rates of subsequent hospital admissions, emergency department presentations and ambulatory mental health treatment days of people hospitalised with different psychotic disorder subtypes to people hospitalised with schizophrenia spectrum disorders using Poisson regression. RESULTS: People most recently hospitalised with mood/affective disorders and psychotic symptoms had a higher rate of subsequent hospital admissions than those most recently hospitalised with schizophrenia spectrum and delusional disorders (adjusted incident rate ratio = 1.06; 95% confidence interval = [1.02, 1.10]), while people most recently hospitalised with drug-induced and other organic (adjusted incident rate ratio = 1.19; 95% confidence interval = [1.12, 1.27]) and acute psychotic disorders (adjusted incident rate ratio = 1.10; 95% confidence interval = [1.03, 1.18]) had more subsequent emergency department presentations than those most recently hospitalised with schizophrenia spectrum and delusional disorders. All three groups had fewer subsequent mental health ambulatory days than those most recently hospitalised with schizophrenia spectrum and delusional disorders (adjusted incident rate ratios = 0.85-0.91). CONCLUSION: The health profiles and subsequent hospital service use patterns of people previously hospitalised with different psychotic disorder subtypes are heterogeneous, and research is needed to develop targeted health policies to meet their specific health needs.

Factors associated with discharge from hospital to residential aged care for younger people with neuropsychiatric disorders: an exploratory case-control study in New South Wales, Australia.

OBJECTIVES: To examine the sociodemographic and diagnostic factors associated with a discharge from hospital to residential aged care (RAC) for younger people (aged 15-64 years) with neuropsychiatric disorders. DESIGN: An exploratory case-control study using a historic cohort of people with neuropsychiatric disorders. Cases were people transferred to RAC on hospital discharge during the study period. Controls were people not transferred to RAC on discharge during the study period. SETTING: Public and private hospital admissions in New South Wales (NSW), Australia. PARTICIPANTS: People aged 15-64 years with a neuropsychiatric disorder hospitalised in NSW between July 2002 and June 2015 (n=5 16 469). OUTCOME MEASURES: The main outcome was transferred to RAC on discharge from hospital. We calculated ORs for sociodemographic and diagnostic factors to determine factors that may impact discharge to RAC. RESULTS: During the period of data capture, 4406 people were discharged from hospitals to RAC. Discharge to RAC was most strongly associated with diagnoses of progressive neurological and cognitive disorders. Acute precipitants of RAC transfer included a broad range of conditions and injuries (eg, Wernicke's encephalopathy, stroke, falls) in the context of issues such as older age, not being partnered (married or de facto), living in areas of lower socioeconomic status, functional issues and the need for palliative care. CONCLUSIONS: There are multiple intersecting and interacting pathways culminating in discharge from hospital to RAC among younger people with neuropsychiatric disorders. Improved capacity for interdisciplinary home care and alternative housing and support options for people with high support needs are required.

Predictors and outcomes of recognition of intellectual disability for adults during hospital admissions: A retrospective data linkage study in NSW, Australia.

Adults with intellectual disability have high health care needs. Despite frequent contact with health services, they often receive inadequate health care. One method to improve health care delivery is reasonable adjustments, that is, the adaptation of health care delivery such that barriers to participation are removed for the person with disability. A starting point for the provision of reasonable adjustments is recognition of intellectual disability during the health care contact. To determine rates and predictors of the recognition of intellectual disability during hospital admissions, and its impact on admission metrics, we examined a population of adults with intellectual disability identified from disability services datasets from New South Wales, Australia between 2005 and 2014. Recognition of intellectual disability was determined by the recording of an International Classification of Diseases 10th revision (ICD-10) diagnostic code for intellectual disability during a given hospital admission. We examined how recognition of intellectual disability related to length of hospital episodes. We found an overall low rate of recognition of intellectual disability (23.79%) across all hospital episodes, with the proportion of hospital episodes recognising intellectual disability decreasing from 2005-2015. Admissions for adults with complex health profiles (e.g., those with many comorbidities, those with Autism Spectrum Disorder, and those admitted for urgent treatment) were more likely to recognise intellectual disability, but admissions for adults with complexity in other domains (i.e., for those in custody, or those with drug and alcohol disorders) were less likely to recognise intellectual disability. Recognition of intellectual disability was associated with longer episodes of care, possibly indicating the greater provision of reasonable adjustments. To improve the recognition of intellectual disability for adults during health service contacts, we advocate for the implementation of targeted initiatives (such as a nationwide disability flag to be included in health service records) to improve the provision of reasonable adjustments.

Data-Driven Techniques for Low-Cost Sensor Selection and Calibration for the Use Case of Air Quality Monitoring.

With the emergence of Low-Cost Sensor (LCS) devices, measuring real-time data on a large scale has become a feasible alternative approach to more costly devices. Over the years, sensor technologies have evolved which has provided the opportunity to have diversity in LCS selection for the same task. However, this diversity in sensor types adds complexity to appropriate sensor selection for monitoring tasks. In addition, LCS devices are often associated with low confidence in terms of sensing accuracy because of the complexities in sensing principles and the interpretation of monitored data. From the data analytics point of view, data quality is a major concern as low-quality data more often leads to low confidence in the monitoring systems. Therefore, any applications on building monitoring systems using LCS devices need to focus on two main techniques: sensor selection and calibration to improve data quality. In this paper, data-driven techniques were presented for sensor calibration techniques. To validate our methodology and techniques, an air quality monitoring case study from the Bradford district, UK, as part of two European Union (EU) funded projects was used. For this case study, the candidate sensors were selected based on the literature and market availability. The candidate sensors were narrowed down into the selected sensors after analysing their consistency. To address data quality issues, four different calibration methods were compared to derive the best-suited calibration method for the LCS devices in our use case system. In the calibration, meteorological parameters temperature and humidity were used in addition to the observed readings. Moreover, we uniquely considered Absolute Humidity (AH) and Relative Humidity (RH) as part of the calibration process. To validate the result of experimentation, the Coefficient of Determination (R2), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE) were compared for both AH and RH. The experimental results showed that calibration with AH has better performance as compared with RH. The experimental results showed the selection and calibration techniques that can be used in designing similar LCS based monitoring systems.

The health service contact patterns of people with psychotic and non-psychotic forms of severe mental illness in New South Wales, Australia: A record-linkage study.

OBJECTIVE: To describe and compare the health profiles and health service use of people hospitalised with severe mental illness, with and without psychotic symptoms. METHODS: We conducted a historical cohort study using linked administrative datasets, including data on public hospital admissions, emergency department presentations and ambulatory mental health service contacts in New South Wales, Australia. The study cohort comprised 169,306 individuals aged 12 years and over who were hospitalised at least once with a mental health diagnosis between 1 July 2002 and 31 December 2014. Of these, 63,110 had a recorded psychotic illness and 106,196 did not. Outcome measures were rates of hospital, emergency department and mental health ambulatory service utilisation, analysed using Poisson regression. RESULTS: People with psychotic illnesses had higher rates of hospital admission (adjusted incidence rate ratio (IRR) 1.26; 95% confidence interval [1.23, 1.30]), emergency department presentation (adjusted IRR 1.17; 95% confidence interval [1.13, 1.20]) and ambulatory mental health treatment days (adjusted IRR 2.90; 95% confidence interval [2.82, 2.98]) than people without psychotic illnesses. The higher rate of hospitalisation among people with psychotic illnesses was driven by mental health admissions; while people with psychosis had over twice the rate of mental health admissions, people with other severe mental illnesses without psychosis (e.g. mood/affective, anxiety and personality disorders) had higher rates of physical health admissions, including for circulatory, musculoskeletal, genitourinary and respiratory disorders. Factors that predicted greater health service utilisation included psychosis, intellectual disability, greater medical comorbidity and previous hospitalisation. CONCLUSION: Findings from this study support the need for (a) the development of processes to support the physical health of people with severe mental illness, including those without psychosis; (b) a focus in mental health policy and service provision on people with complex support needs, and (c) improved implementation and testing of integrated models of care to improve health outcomes for all people experiencing severe mental illness.

Protection from uncertainty in the exploration/exploitation trade-off.

The exploration/exploitation trade-off (EE trade-off) describes how, when faced with several competing alternatives, decision-makers must often choose between a known good alternative (exploitation) and one or more unknown but potentially more rewarding alternatives (exploration). Prevailing theory on how humans perform the EE trade-off states that uncertainty is a major motivator for exploration: the more uncertain the environment, the more exploration that will occur. The current article examines whether exploratory behavior in both choice and attention may be impacted differently depending on whether uncertainty is onset suddenly (unexpected uncertainty), or more slowly (expected uncertainty). It is shown that when uncertainty was expected, participants tended to explore less with their choices, but not their attention, than when it was unexpected. Crucially, the impact of this "protection from uncertainty" on exploration only occurred when participants had an opportunity to learn the structure of the task before experiencing uncertainty. This suggests that the interaction between uncertainty and exploration is more nuanced than simply more uncertainty leading to more exploration, and that attention and choice behavior may index separate aspects of the EE trade-off. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Out of fright, out of mind: impaired memory for information negated during looming threat.

People often need to update representations of information upon discovering them to be incorrect, a process that can be interrupted by competing cognitive demands. Because anxiety and stress can impair cognitive performance, we tested whether looming threat can similarly interfere with the process of updating representations of a statement's truthfulness. On each trial, participants saw a face paired with a personality descriptor. Each pairing was followed by a signal indicating whether the pairing was "true", or "false" (a negation of the truth of the statement), and this signal could be followed by a warning of imminent electric shock (i.e., the looming threat). As predicted, threat of shock left memory for "true" pairings intact, while impairing people's ability to label negated pairings as untrue. Contrary to our predictions, the pattern of errors for pairings that were negated under threat suggested that these mistakes were at least partly attributable to participants forgetting that they saw the negated information at all (rather than being driven by miscategorization of the pairings as true). Consistent with this, linear ballistic accumulator modelling suggested that this impaired recognition stemmed from weaker memory traces rather than decisional processes. We suggest that arousal due to looming threat may interfere with executive processes important for resolving competition between mutually suppressive tags of whether representations in memory are "true" or "false".

The role of uncertainty in attentional and choice exploration.

The exploitation-exploration (EE) trade-off describes how, when making a decision, an organism must often choose between a safe alternative with a known pay-off, and one or more riskier alternatives with uncertain pay-offs. Recently, the concept of the EE trade-off has been extended to the examination of how organisms distribute limited attentional resources between several stimuli. This work suggests that when the rules governing the environment are certain, participants learn to "exploit" by attending preferentially to cues that provide the most information about upcoming events. However, when the rules are uncertain, people "explore" by increasing their attention to all cues that may provide information to help in predicting upcoming events. In the current study, we examine how uncertainty affects the EE trade-off in attention using a contextual two-armed bandit task, where participants explore with both their attention and their choice behavior. We find evidence for an influence of uncertainty on the EE trade-off in both choice and attention. These findings provide support for the idea of an EE trade-off in attention, and that uncertainty is a primary motivator for exploration in both choice and attentional allocation.

A complex flow phantom for medical imaging: ring vortex phantom design and technical specification.

Cardiovascular fluid dynamics exhibit complex flow patterns, such as recirculation and vortices. Quantitative analysis of these complexities supports diagnosis, leading to early prediction of pathologies. Quality assurance of technologies that image such flows is challenging but essential, and to this end, a novel, cost-effective, portable, complex flow phantom is proposed and the design specifications are provided. The vortex ring is the flow of choice because it offers patterns comparable to physiological flows and is stable, predictable, reproducible and controllable. This design employs a piston/cylinder system for vortex ring generation, coupled to an imaging tank full of fluid, for vortex propagation. The phantom is motor-driven and by varying piston speed, piston displacement and orifice size, vortex rings with different characteristics can be produced. Two measurement methods, namely Laser-PIV and an optical/video technique, were used to test the phantom under a combination of configurations. Vortex rings with a range of travelling velocities (approximately 1-80 cm/s) and different output-orifice diameters (10-25 mm) were produced with reproducibility typically better than ±10%. Although ultrasound compatibility has been demonstrated, longer-term ambitions include adapting the design to support comparative studies with different modalities, such as MRA and X-ray-CTA.

Development of an anatomically correct mouse phantom for dosimetry measurement in small animal radiotherapy research.

Significant improvements in radiotherapy are likely to come from biological rather than technical optimization, for example increasing tumour radiosensitivity via combination with targeted therapies. Such paradigms must first be evaluated in preclinical models for efficacy, and recent advances in small animal radiotherapy research platforms allow advanced irradiation protocols, similar to those used clinically, to be carried out in orthotopic models. Dose assessment in such systems is complex however, and a lack of established tools and methodologies for traceable and accurate dosimetry is currently limiting the capabilities of such platforms and slowing the clinical uptake of new approaches. Here we report the creation of an anatomically correct phantom, fabricated from materials with tissue-equivalent electron density, into which dosimetry detectors can be incorporated for measurement as part of quality control (QC). The phantom also allows training in preclinical radiotherapy planning and cross-institution validation of dose delivery protocols for small animal radiotherapy platforms without the need to sacrifice animals, with high reproducibility. Mouse CT data was acquired and segmented into soft tissue, bone and lung. The skeleton was fabricated using 3D printing, whilst lung was created using computer numerical control (CNC) milling. Skeleton and lung were then set into a surface-rendered mould and soft tissue material added to create a whole-body phantom. Materials for fabrication were characterized for atomic composition and attenuation for x-ray energies typically found in small animal irradiators. Finally cores were CNC milled to allow intracranial incorporation of bespoke detectors (alanine pellets) for dosimetry measurement.

Endotoxin-induced cerebral pathophysiology: differences between fetus and newborn.

As the comparative pathophysiology of perinatal infection in the fetus and newborn is uncertain, this study contrasted the cerebral effects of endotoxemia in conscious fetal sheep and newborn lambs. Responses to intravenous bacterial endotoxin (lipopolysaccharide, LPS) or normal saline were studied on three consecutive days in fetal sheep (LPS 1 µg/kg, n = 5; normal saline n = 5) and newborn lambs (LPS 2 µg/kg, n = 10; normal saline n = 5). Cerebro-vascular function was assessed by monitoring cerebral blood flow (CBF) and cerebral vascular resistance (CVR) over 12 h each day, and inflammatory responses were assessed by plasma TNF alpha (TNF-α), nitrate and nitrite concentrations. Brain injury was quantified by counting both resting and active macrophages in the caudate nucleus and periventricular white matter (PVWM). An acute cerebral vasoconstriction (within 1 h of LPS injection) occurred in both the fetus (ΔCVR +53%) and newborn (ΔCVR +63%); subsequently prolonged cerebral vasodilatation occurred in the fetus (ΔCVR -33%) in association with double plasma nitrate/nitrite concentrations, but not in the newborn. Abundant infiltration of activated macrophages was observed in both CN and PVWM at each age, with the extent being 2-3 times greater in the fetus (P < 0.001). In conclusion, while the fetus and newborn experience a similar acute disruption of the cerebral circulation after LPS, the fetus suffers a more prolonged circulatory disruption, a greater infiltration of activated macrophages, and an exaggerated susceptibility to brain injury.

Recombinant human G6PD for quality control and quality assurance of novel point-of-care diagnostics for G6PD deficiency.

BACKGROUND: A large gap for the support of point-of-care testing is the availability of reagents to support quality control (QC) of diagnostic assays along the supply chain from the manufacturer to the end user. While reagents and systems exist to support QC of laboratory screening tests for glucose-6-phosphate dehydrogenase (G6PD) deficiency, they are not configured appropriately to support point-of-care testing. The feasibility of using lyophilized recombinant human G6PD as a QC reagent in novel point-of-care tests for G6PD deficiency is demonstrated. METHODS: Human recombinant G6PD (r-G6PD) was expressed in Escherichia coli and purified. Aliquots were stored at -80°C. Prior to lyophilization, aliquots were thawed, and three concentrations of r-G6PD (representing normal, intermediate, and deficient clinical G6PD levels) were prepared and mixed with a protective formulation, which protects the enzyme activity against degradation from denaturation during the lyophilization process. Following lyophilization, individual single-use tubes of lyophilized r-G6PD were placed in individual packs with desiccants and stored at five temperatures for one year. An enzyme assay for G6PD activity was used to ascertain the stability of r-G6PD activity while stored at different temperatures. RESULTS: Lyophilized r-G6PD is stable and can be used as a control indicator. Results presented here show that G6PD activity is stable for at least 365 days when stored at -80°C, 4°C, 30°C, and 45°C. When stored at 55°C, enzyme activity was found to be stable only through day 28. CONCLUSIONS: Lyophilized r-G6PD enzyme is stable and can be used as a control for point-of-care tests for G6PD deficiency.

The Effect of Gestational Age at Birth on Post-Term Maturation of Heart Rate Variability.

STUDY OBJECTIVE: Preterm birth delays maturation of autonomic cardiovascular control, reflected in reduced heart rate variability (HRV) in preterm compared to term infants at term-equivalent age. It has been suggested that immature cardiovascular control contributes to the increased risk for the sudden infant death syndrome (SIDS) in preterm infants. However, the effects of prone sleeping, the major SIDS risk factor, and of gestational age (GA) at birth on HRV have not been assessed in preterm infants beyond term-equivalent age. SUBJECTS AND METHODS: Very preterm (n = 21; mean GA 29.4 ± 0.3 weeks), preterm (n = 14; mean GA 33.5 ± 0.3 weeks), and term (n = 17; mean GA 40.1 ± 0.3 weeks) infants were recruited and underwent daytime polysomnography at 2-4 weeks, 2-3 months, and 5-6 months post-term corrected age (CA). Infants slept both supine and prone. HRV was assessed in the low frequency (LF) and high frequency (HF) ranges. RESULTS: There was no effect of prone sleeping on HRV parameters in either preterm group. In term infants LF/HF was significantly elevated in the prone position in AS at 2-4 weeks (P < 0.05). HF HRV was significantly reduced (P < 0.05) and LF/HF increased (P < 0.05) in very preterm compared to both preterm and term infants at 2-3 months CA. CONCLUSION: Prone sleeping did not significantly impact on heart rate variability (HRV) in preterm infants. However, reduced maturation of high frequency HRV in very preterm infants resulted in significantly altered sympathovagal balance at 2-3 months corrected age, the age of peak sudden infant death syndrome (SIDS) risk. This may contribute to the increased risk of SIDS in infants born at earlier gestational age.

Preterm Infants Exhibit Greater Variability in Cerebrovascular Control than Term Infants.

STUDY OBJECTIVES: Sudden infant death syndrome (SIDS) remains an important cause of infant death, particularly among infants born preterm. Prone sleeping is the major risk factor for SIDS and this has recently been shown to alter cerebrovascular control in term infants. As preterm infants are at greater risk for SIDS than those born at term, we hypothesized that their cerebrovascular control in the prone position would be reduced compared to term infants. PATIENTS OR PARTICIPANTS: There were 35 preterm (mean gestation 31.2 ± 0.4 w) and 17 term (mean gestation 40.1 ± 0.3 w) infants. DESIGN: Infants underwent daytime polysomnography at 2-4 w, 2-3 mo, and 5-6 mo postterm age. Infants slept both prone and supine and were presented with cardiovascular challenges in the form of 15° head-up tilts (HUT). MEASUREMENTS AND RESULTS: Cerebral tissue oxygenation index (TOI) was recorded using near-infrared spectroscopy (NIRO-200 spectrophotometer, Hamamatsu Photonics KK, Japan) and mean arterial pressure (MAP) was recorded using a Finometer cuff (Finapres Medical Systems, Amsterdam, The Netherlands). In the prone position TOI increased following the HUT (P < 0.05), whereas no change was seen in the supine position. The overall pattern of response was similar in both groups, but more variable in preterm than term infants (P < 0.05). CONCLUSIONS: Cerebrovascular control differs between the prone and supine positions in preterm infants. Although overall the responses to head-up tilts were similar between term and preterm infants, greater variability of responses in preterm infants suggests persisting immaturity of their cerebrovascular control in the first year of life, which may contribute to their increased risk of sudden infant death syndrome.

Gestational age at birth affects maturation of baroreflex control.

OBJECTIVES: To assess the effect of prone sleeping, the major risk factor for sudden infant death syndrome, in the control of blood pressure (BP) in preterm infants born across a range of gestational ages. STUDY DESIGN: Daytime polysomnography was performed at 2-4 weeks, 2-3 months, and 5-6 months postterm age. The participants were 21 very preterm (mean gestation 29.4 ± 0.3 weeks), 14 preterm (mean gestation 33.1 ± 0.3 weeks), and 17 term (mean gestation 40.1 ± 0.3 weeks). BP was measured via a Finometer cuff (Finapres Medical Systems, Amsterdam, The Netherlands) placed around the wrist. Data were recorded both supine and prone. Baroreflex sensitivity (BRS) was calculated via cross-spectral analysis of spontaneous fluctuations in BP. RESULTS: BRS was lower in the prone position in very preterm infants at 2-4 weeks in active sleep (P < .05). Maturation of BRS was delayed in very preterm compared with both preterm and term infants. CONCLUSIONS: Maturation of BRS after term-equivalent age is altered in very preterm infants. Reduced BRS may result in an impaired ability of very preterm infants to respond to cardiovascular stress during infancy and may predispose them to cardiovascular disease later in life.

Cerebral oxygenation in preterm infants.

BACKGROUND AND OBJECTIVE: Prone sleeping is a major risk factor for sudden infant death syndrome (SIDS) and preterm infants are at significantly increased risk. In term infants, prone sleeping is associated with reduced mean arterial pressure (MAP) and cerebral tissue oxygenation index (TOI). However, little is known about the effects of sleeping position on TOI and MAP in preterm infants. We aimed to examine TOI and MAP in preterm infants after term-equivalent age, during the period of greatest SIDS risk. METHODS: Thirty-five preterm and 17 term infants underwent daytime polysomnography, including measurement of TOI (NIRO-200 spectrophotometer, Hamamatsu Photonics KK, Japan) and MAP (Finapress Medical Systems, Amsterdam, Netherlands) at 2 to 4 weeks, 2 to 3 months, and 5 to 6 months postterm age. Infants slept prone and supine in active and quiet sleep. The effects of sleep state and position were determined by using 2-way repeated measures analysis of variance and of preterm birth by using 2-way analysis of variance. RESULTS: In preterm infants, TOI was significantly lower when prone compared with supine in both sleep states at all ages (P < .05). Notably, TOI was significantly lower in preterm compared with term infants at 2 to 4 weeks, in both positions (P < .05), and at 2 to 3 months when prone (P < .001), in both sleep states. MAP was also lower in preterm infants in the prone position at 2 to 3 months (P < .01). CONCLUSIONS: Cerebral oxygenation is reduced in the prone position in preterm infants and is lower compared with age-matched term infants, predominantly in the prone position when MAP is also reduced. This may contribute to their increased SIDS risk.