Daytime Measures Research Articles

Heart Rate Variability, Deceleration Capacity of Heart Rate, and Death: A Veteran Twins Study.

Autonomic function can be measured noninvasively using heart rate variability (HRV), which indexes overall sympathovagal balance. Deceleration capacity (DC) of heart rate is a more specific metric of vagal modulation. Higher values of these measures have been associated with reduced mortality risk primarily in patients with cardiovascular disease, but their significance in community samples is less clear. This prospective twin study followed 501 members from the VET (Vietnam Era Twin) registry. At baseline, frequency domain HRV and DC were measured from 24-hour Holter ECGs. During an average 12-year follow-up, all-cause death was assessed via the National Death Index. Multivariable Cox frailty models with random effect for twin pair were used to examine the hazard ratios of death per 1-SD increase in log-transformed autonomic metrics. Both in the overall sample and comparing twins within pairs, higher values of low-frequency HRV and DC were significantly associated with lower hazards of all-cause death. In within-pair analysis, after adjusting for baseline factors, there was a 22% and 27% lower hazard of death per 1-SD increment in low-frequency HRV and DC, respectively. Higher low-frequency HRV and DC, measured during both daytime and nighttime, were associated with decreased hazard of death, but daytime measures showed numerically stronger associations. Results did not substantially vary by zygosity. Autonomic inflexibility, and especially vagal withdrawal, are important mechanistic pathways of general mortality risk, independent of familial and genetic factors.

Abstract 118: Effects Of Aprocitentan, A Dual Endothelin Receptor Antagonist, On Blood Pressure In Black/African American Patients With Resistant Hypertension: Results From A Randomized, Controlled Study (PRECISION) Including A Withdrawal Phase

Background: Resistant hypertension is prevalent among Black/African American drug-treated hypertensives and may increase cardiovascular risk. We evaluated aprocitentan (APRO) for BP lowering in Black patients with resistant hypertension. Methods: Patients had sitting unattended automated office systolic BP (SBP) ≥140 mmHg despite use of ≥3 antihypertensives of different classes in the year prior. After 4 weeks of combination therapy (amlodipine, valsartan, hydrochlorothiazide), those still hypertensive could enter a 4-week single-blind placebo (PBO) run-in period, followed by a 4-week double-blind period wherein patients were randomized 1:1:1 to APRO 12.5 mg, 25 mg, or PBO. A 32-week single-blind period on APRO 25 mg followed. Patients were then re-randomized 1:1 to APRO 25 mg or PBO in a 12-week withdrawal period. The primary endpoint was change from baseline to Week 4 in mean trough SBP. Changes in SBP from withdrawal baseline (Week 36) to Week 40 and in 24-hour, daytime (09:00-21:00), and nighttime (01:00-06:00) ambulatory BP monitoring (ABPM) measures at Weeks 4 and 40 were also assessed. Results: Eighty-two of 730 patients (11.2%) were Black (APRO 12.5 mg, n = 28; 25 mg, n = 28; PBO, n = 26). At Week 4, APRO and PBO produced similar office SBP reductions (least squares mean difference from PBO, 12.5 mg: 0.63 mmHg; 25 mg: 0.12 mmHg). However, APRO produced pronounced reductions vs PBO in mean 24-hour (12.5 mg: –3.23 mmHg; 25 mg: –7.85 mmHg), daytime (12.5 mg: –6.16 mmHg; 25 mg: –9.13 mmHg), and nighttime (12.5 mg: –2.63 mmHg; 25 mg: –8.53 mmHg) ambulatory SBP. Four weeks after withdrawal, office SBP increased with PBO vs APRO 25 mg (difference: +9.87 mmHg), which was confirmed with ambulatory SBP (difference, 25 mg; 24-hour: +8.13 mmHg, daytime: +3.39 mmHg, nighttime: +9.70 mmHg). Safety in Black patients was comparable to the overall population, with no new signals. During the double-blind period, treatment-emergent adverse events were reported in 6/28 (21.4%), 9/29 (31.0%), and 4/25 (16.0%) patients with APRO 12.5 mg, APRO 25 mg, and PBO. Edema or fluid retention occurred in 3/29 patients (10.3%) on APRO 25 mg, and no patients on APRO 12.5 mg or PBO. Conclusion: APRO was well tolerated and produced clinically relevant reductions in SBP by ABPM in Black patients.

Arterial stiffness and its influence on cerebral morphology and cognitive function.

Recently, arterial stiffness has been associated with cerebral small vessel disease (SVD), brain atrophy and vascular dementia. Arterial stiffness is assessed via pulse wave velocity (PWV) measurement and is strongly dependent on arterial blood pressure. While circadian blood pressure fluctuations are important determinants of end-organ damage, the role of 24-h PWV variability is yet unclear. We here investigated the association between PWV and its circadian changes on brain morphology and cognitive function in community-dwelling individuals. Single-centre, prospective, community-based follow-up study. The study cohort comprised elderly community-based participants of the Austrian Stroke Prevention Family Study which was started in 2006. Patients with any history of cerebrovascular disease or dementia were excluded. The study consists of 84 participants who underwent ambulatory 24-h PWV measurement. White matter hyperintensity volume and brain volume were evaluated by 3-Tesla magnetic resonance imaging (MRI). A subgroup of patients was evaluated for cognitive function using an extensive neuropsychological test battery. PWV was significantly related to reduced total brain volume (p = 0.013), which was independent of blood pressure and blood pressure variability. We found no association between PWV with markers of cerebral SVD or impaired cognitive functioning. Only night-time PWV values were associated with global brain atrophy (p = 0.005). This study shows a relationship of arterial stiffness and reduced total brain volume. Elevations in PWV during night-time are of greater importance than day-time measures.

Nocturnal Delta Power is Associated With Lower Next-Day Pain But Not Pain Catastrophizing: Results From a Cohort of Female Participants With Temporomandibular Joint Pain

Existing data demonstrate reduced delta power during sleep in patients with depression and chronic pain. However, there has been little examination of the relationship between delta power and pain-reports, or pain-catastrophizing. We recruited female participants (n = 111) with insomnia and temporomandibular disorder, and measured nocturnal and daytime measures of pain and pain catastrophizing, and calculated relative nocturnal delta (0.5–4 Hz) power during sleep. We fit linear regression models, and further examined the moderating effect of depressive symptom severity. Lower relative delta power across the whole night was significantly associated with greater nocturnal pain (B = -20.276, P = .025, R2 = 0.214). Lower relative delta power during the first-third of the night, was associated with greater nocturnal pain (B = -17.807, p = 0.019, R2 = 0.217), next-day pain (B = 13.876, P = .039, R2 = 0.195), and next-morning pain (B = -15.751, P = .022, R2 = 0.198). Lower relative delta power during the final-third of the night was significantly associated with greater nocturnal (B = -17.602, P = .029, R2 = 0.207) and next-morning pain (3rd: B = -14.943, P = .042, R2 = 0.187). Depressive symptom severity did not moderate these relationships. Delta power was not significantly associated with nocturnal or daytime pain catastrophizing. These findings demonstrate that greater relative delta power during sleep is associated with lower nocturnal and next-day pain in patients with temporomandibular disorder. This data may guide the use of sleep interventions in clinical pain populations, with the aim of improving pain outcomes. PerspectiveThis article presents data demonstrating an association between increased nocturnal delta power and reduced next-day pain. These findings may help promote interventions which aim to increase nocturnal delta power in clinical pain populations, with the goal of improving pain outcomes.

Twenty-Four-Hour Central Hemodynamic Load in Adults With and Without a History of COVID-19.

BACKGROUNDAlthough hypertension is an established risk factor for severe COVID-19 illness, little is known about the effects of COVID-19 on blood pressure (BP). Central BP measures taken over a 24-hour period using ambulatory blood pressure monitoring (ABPM) adds prognostic value in assessing cardiovascular disease (CVD) risk compared to brachial BP measures taken at a single time point. We assessed CVD risk between adults with and without a history of COVID-19 via appraisal of 24-hour brachial and central hemodynamic load from ABPM.METHODSCross-sectional analysis was performed on 32 adults who tested positive for COVID-19 (29±13 years, 22 females) and 43 adults without a history of COVID-19 (28±12 years, 26 females). Measures of 24-hour hemodynamic load included brachial and central systolic and diastolic BP, pulse pressure, augmentation index (AIx), pulse wave velocity (PWV), nocturnal BP dipping, the ambulatory arterial stiffness index (AASI), and the blood pressure variability ratio (BPVR).RESULTSParticipants who tested positive for COVID-19 experienced 6±4 COVID-19 symptoms, were studied 122±123 days after testing positive, and had mild-to-moderate COVID-19 illness. The results from independent samples t-tests showed no significant differences in any of our 24-hour, daytime, or nighttime measures of central or peripheral hemodynamic load across those with and without a history of COVID-19 (p > 0.05 for all).CONCLUSIONSNo differences in 24-hour brachial or central ABPM measures were detected between adults recovering from mild-to-moderate COVID-19 and controls without a history of COVID-19. Adults recovering from mild-to-moderate COVID-19 do not have increased 24-hour central hemodynamic load.

Non-pharmacological interventions for sleep promotion in hospitalized children.

Non-pharmacological interventions for sleep promotion in hospitalized children.

Night-to-night variation in sleep associates with day-to-day variation in vigilance, cognition, memory, and behavioral problems in Alzheimer's disease.

IntroductionSleep disturbances are commonly reported in people living with Alzheimer's disease (AD), but it is currently unknown whether night‐to‐night variation in sleep predicts day‐to‐day variation in vigilance, cognition, mood, and behavior (daytime measures).MethodsSubjective and objective sleep and daytime measures were collected daily for 2 weeks in 15 participants with mild AD, eight participants with mild cognitive impairment (MCI), and 22 participants with no cognitive impairment (NCI). Associations between daytime measures and four principal components of sleep (duration, quality, continuity, and latency) were quantified using mixed‐model regression.ResultsSleepiness, alertness, contentedness, everyday memory errors, serial subtraction, and behavioral problems were predicted by at least one of the components of sleep, and in particular sleep duration and continuity. Associations between variations in sleep and daytime measures were linear or quadratic and often different between participants with AD and those with NCI.DiscussionThese findings imply that daytime functioning in people with AD may be improved by interventions that target sleep continuity.

How Cattle and Wild Ungulate Use of Riparian Areas Effects Measures of Streambank Disturbance

Improper management of cattle near streams can negatively affect the processes that support stream and riparian ecosystems. To judge the success of riparian management strategies, public land management agencies often evaluate two metrics of livestock disturbance, stubble height and streambank alteration. There are concerns associated with how well these disturbance metrics reflect livestock use and incorporate additional effects due to wild ungulates. We sought to address these questions in 39 riparian areas by using time-lapse cameras to estimate ungulate use and then measuring near stream ungulate disturbance in these same reaches. We found daytime measures of livestock use were related to stubble height and streambank alteration. Explaining the variation in the relationship between stubble height and livestock use was improved by incorporating covariates, whereas covariates did little to improve our understanding of streambank alteration. This suggests greater flexibility in how different stream reaches are managed when stubble height is the guideline. As streambank alteration was explained solely by ungulate use, the simplest way to reduce disturbance was to reduce use. In most stream reaches, the additive presence of wild ungulates was minimal but sufficient to be included in the best models describing the effects of ungulate disturbance. On most days, no cattle were seen in the evaluated riparian reaches. Although large groups of cattle (> 20 individuals) were occasionally observed within riparian areas, they generally occurred in small groups of one to four individuals. Across the riparian reaches we evaluated, cattle presence and density were generally low enough that metrics of livestock disturbance suggested little risk to stream conditions important to aquatic biota. However, there were some riparian areas where cattle stayed too long or occurred in large enough numbers that their use along the streambanks could negatively affect stream habitat conditions.

Nocturnal thoracic volume overload and post‐discharge outcomes in patients hospitalized for acute heart failure

AimsVolume overload and perturbations of pulsatile haemodynamics may precipitate acute heart failure (AHF). Nocturnal thoracic volume overload due to rostral fluid shift during recumbency undetected by daytime measures may impact nighttime haemodynamics and post‐discharge outcomes.Methods and resultsA total of 63 patients (median 60 years, 79.4% men, and left ventricular ejection fraction 29.4%) hospitalized for AHF were enrolled. Once clinical euvolaemia was achieved, noninvasive pulsatile haemodynamics were assessed during daytime followed by circadian monitoring (6 p.m. to 5 a.m.) of thoracic fluid content and thoracic fluid content index (TFCi) using impedance cardiography, normalized electromechanical activation time ratio (EMAT%) using acoustic cardiography, and mean blood pressure using ambulatory blood pressure monitoring before discharge. The primary endpoints were composited of the first hospitalization for heart failure and death from any cause. Patients were also followed for the repeated heart failure hospitalizations. During a median follow‐up duration of 16 months, 33 patients encountered primary composite endpoints (52.4%), and there were 42 hospitalizations developed among 25 patients. An overnight increase in TFCi along with persistently prolonged EMAT% and low mean blood pressure was observed in the eventful group. Overnight increase in TFCi (ΔTFCi, the difference between the measures at 4 a.m. and 6 p.m.) was an independent predictor of primary composite events (hazard ratio and 95% confidence interval: 1.58, 1.07–2.33; P = 0.022) and recurrent composite events (2.22, 1.51–3.26; P < 0.001), after adjusting for potential confounding factors. A high ΔTFCi (≥0.5/kΩ/m2) significantly correlated with higher post‐discharge events (hazard ratio 6.25; 95% confidence interval 2.30–16.96; P < 0.001) in comparison with a low ΔTFCi (<0.5/kΩ/m2). ΔTFCi was significantly associated with EMAT%, estimated glomerular filtration rate, and left ventricular ejection fraction, but not with parameters of pulsatile haemodynamics.ConclusionsNocturnal thoracic volume overload in AHF before discharge, indicating the presence of residual volume overload unidentified by daytime measures, may predict post‐discharge outcomes.

Diurnal rhythm of blood pressure in patients with polycythemia vera.

Polycythemia vera increases the risk of hypertension, but there is limited information about the effect on daily blood pressure fluctuations. This study aimed to demonstrate how diurnal blood pressure rhythm is affected in polycythemia vera patients. Fifty (50) patients (33 men; mean age 48 ± 15 years) with a diagnosis of polycythemia vera and 51 age and sex-matched healthy subjects for the control group were prospectively evaluated. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were evaluated by ambulatory blood pressure monitoring (ABPM) as average 24-hour, daytime and nighttime measures. Average 24-hour SBP and DBP, daytime SBP and DBP were similar in both groups. However, nighttime SBP and DBP were significantly higher in the polycythemia vera group compared with the control group (125.3 ± 17.2 and 73.7 ± 12.2 vs. 118.9 ± 12.2 and 69.5 ± 8.5; P = 0.034 and P = 0.044). Both nocturnal SBP fall and nocturnal DBP fall were blunted in the polycythemia vera group compared with the control group (-6.9 ± 8.9 and -11.3 ± 12.2 vs. -11.6 ± 7.7 and -16.3 ± 12.0, respectively). Both hemoglobin and hematocrit levels were positively correlated with nocturnal SBP fall (r = 0.306, P = 0.002 and r = 0.355, P < 0.001; respectively) in all patients. We found that the polycythemia vera group had significantly decreased nocturnal dipping compared with healthy controls. The SBP fall was also positively correlated with hemoglobin and hematocrit levels.

Association between excessive daytime sleepiness and measures of supraventricular arrhythmia burden: evidence from the Atherosclerosis Risk in Communities (ARIC) study.

Excessive daytime sleepiness is a common sleep complaint among older adults. Assessment of excessive daytime sleepiness is used to screen for obstructive sleep apnea, which may be linked to atrial fibrillation (AF) and other sustained arrhythmias. Using data from the Atherosclerosis Risk in Communities (ARIC) Study cohort, we examined the association of excessive daytime sleepiness with measures of arrhythmia burden derived from a continuous ECG recording device in a community-based sample of older adults. Participating older adults (N= 2306, mean age: 78.9 ± 4.5years, 57.8% female) wore a Zio® XT Patch for 14days. Excessive daytime sleepiness was assessed with the Epworth Sleepiness Scale. Measures of AF and supraventricular arrhythmia burden were derived from the Zio® XT Patch. Multiple adjusted logistic, multinomial, and linear regression models were used to assess associations of excessive daytime sleepiness with AF, AF burden, and supraventricular arrhythmia burden. Approximately 18% of the sample had excessive daytime sleepiness, and 8.5% had AF. After adjustment, excessive daytime sleepiness was not significantly associated with AF (odds ratio (OR), 1.20; Confidence Interval (CI), 0.81-1.75), continuous AF burden (OR, 1.36; CI, 0.85-2.16), or measures of supraventricular arrhythmia burden (SVE burden: β 0.01; 95% CI, -0.09-0.11; SVT burden: β 0.02; 95% CI, -0.04-0.08). In this community-based sample of older adults, excessive daytime sleepiness was not associated with measures of arrhythmia burden. Future studies with objective measures of sleep are needed to further examine the role of sleep in the development and progression of arrhythmia burden.

A Pilot, Randomized Clinical Trial of Bedtime Doses of Prazosin Versus Placebo in Suicidal Posttraumatic Stress Disorder Patients With Nightmares.

Observational studies show an association between nightmares and suicide. Prazosin is proposed as a nightmare treatment. This pilot, randomized clinical trial tested whether treatment of nightmares with prazosin would reduce suicidal ideas in suicidal posttraumatic stress disorder (PTSD) patients. Twenty adult, suicidal PTSD patients with nightmares were blindly and randomly assigned 1:1 to escalating doses of prazosin versus placebo at bedtime only for 8 weeks. All participants had comorbid mood disorders and received stable doses of mood disorder medication. Outcomes of interest were measured weekly and included severity of suicidal ideation, nightmares, PTSD, insomnia, and depression. Longitudinal mixed-effects models assessed change in outcomes over time. All psychometric measures improved over 8 weeks. However, nighttime measures of nightmares and insomnia showed significantly less improvement in the prazosin group, whereas there was no significant change in daytime measures of suicidal ideation and daytime-only PTSD symptoms. Two patients required emergency psychiatric hospitalization, but there were no suicide attempts and no deaths. This study confirmed an effect of nighttime-only prazosin on nighttime symptoms of insomnia and nightmares in suicidal PTSD patients who are experiencing nightmares. Surprisingly, the effect was in the direction opposite of what we expected. Furthermore, prazosin showed no signal on daytime measures including suicidal ideation. The results do not support a larger study of nighttime-only prazosin in suicidal PTSD patients but leave open the possibility of benefit from daytime administration of prazosin.

Obesity Hypoventilation Syndrome: Early Detection of Nocturnal-Only Hypercapnia in an Obese Population.

Hypoventilation in obesity is now divided into five stages; stage 0 (pure obstructive sleep apnea; OSA), stages I/II (obesity-related sleep hypoventilation; ORSH) and stages III/IV (awake hypercapnia, obesity hypoventilation syndrome; OHS). Hypercapnia during the day may be preceded by hypoventilation during sleep. The goal of this study was to determine the prevalence and to identify simple clinical measures that predict stages I/II ORSH. The effect of supine positioning on selected clinical measures was also evaluated. Ninety-four patients with a body mass index > 40 kg/m2 and a spirometric ratio > 0.7 were randomized to begin testing either in the supine or upright seated position on the day of their diagnostic sleep study. Arterialized capillary blood gases were measured in both positions. Oxygen saturation measured by pulse oximetry was also obtained while awake. Transcutaneous CO2 monitoring was performed during overnight polysomnography. Stages I/II ORSH had a prevalence of 19% in an outpatient tertiary hospital setting compared with 61%, 17%, and 3% for stages 0, III/IV, and no sleep-disordered breathing respectively. Predictors for sleep hypoventilation in this group were an awake oxygen saturation of ≤ 93% (sensitivity 39%, specificity 98%, positive likelihood ratio of 22) and a partial pressure of carbon dioxide ≥ 45 mmHg (sensitivity 44%, specificity 98%, positive likelihood ratio of 24) measured in the supine position. ORSH has a similar prevalence to OHS. Awake oxygen saturation and partial pressure of carbon dioxide performed in the supine position may help predict obese patients with sleep hypoventilation without awake hypercapnia. A commentary on this article appears in this issue on page 1455. Registry: Australian New Zealand Clinical Trials Registry, Identifier: ACTRN 12615000135516, URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=367493&isReview=true, Title: A cross-sectional study to identify obese patients who are at risk for developing obesity hypoventilation syndrome (OHS) by investigating the relationship between daytime measures (including supine hypercapnia, distribution of body fat and lung volumes) with the presence of hypoventilation during sleep.

Stability and change in daytime and nighttime sleep in children attending daycare

Many young children experience insufficient or poor quality sleep, which may have implications for adjustment and cognitive performance. This study tested group-level changes and rank-order stability in both daytime and nighttime sleep parameters over a six-month period, from fall to spring, among children receiving high-quality, center-based daycare. A total of 68 preschoolers (54% girls; Mage = 3.80 years, SD = .68) participated. Sleep was assessed via actigraphy for seven days and nights; sleep duration (actual sleep minutes) and quality parameters were derived. Analyses of group-level changes indicated that children’s daytime and nighttime sleep duration did not change significantly from fall to spring. Nighttime sleep quality showed significant improvement, however, such that children had higher sleep efficiency in the spring than in the fall. Rank-order stability in both nighttime and daytime measures of sleep duration and quality was moderate, and stability in daytime sleep quality was low. Results add to a sparse literature examining stability in sleep parameters in young children using actigraphy.

Xanthine oxidase inhibition for the improvement of long-term outcomes following ischaemic stroke and transient ischaemic attack (XILO-FIST) - Protocol for a randomised double blind placebo-controlled clinical trial.

BackgroundAllopurinol, a xanthine oxidase inhibitor, reduced progression of carotid-intima media thickness and lowered blood pressure in a small clinical trial in people with ischaemic stroke. Xanthine oxidase inhibition for improvement of long-term outcomes following ischaemic stroke and transient ischaemic attack (XILO-FIST) aims to assess the effect of allopurinol treatment on white matter hyperintensity progression and blood pressure after stroke. This paper describes the XILO-FIST protocol.MethodsXILO-FIST is a multicentre randomised double-blind, placebo-controlled, parallel group clinical trial funded by the British Heart Foundation and the Stroke Association. The trial has been adopted by the Scottish Stroke Research Network and the UK Clinical Research Network. The trial is registered in clinicaltrials.gov (registration number NCT02122718). XILO-FIST will randomise 464 participants, aged greater than 50 years, with ischaemic stroke within the past month, on a 1:1 basis, to two years treatment with allopurinol 300 mg twice daily or placebo. Participants will undergo brain magnetic resonance imaging, cognitive assessment, ambulatory blood pressure monitoring and blood sampling at baseline and after two years treatment. The primary outcome will be white matter hyperintensity progression, measured using the Rotterdam progression scale. Secondary outcomes will include change in white matter hyperintensity volume, mean day-time systolic blood pressure and measures of cognitive function. Up to 100 will undergo additional cardiac magnetic resonance imaging in a sub-study of left ventricular mass.DiscussionIf white matter hyperintensity progression is reduced, allopurinol could be an effective preventative treatment for patients with ischaemic stroke and clinical endpoint studies would be needed. If allopurinol reduces blood pressure after stroke, then it could be used to help patients reach blood pressure targets.

Can Daytime Measures of Respiratory Sinus Arrhythmia and Breathing Stability Serve as Biomarkers for OSA?

Obstructive sleep apnea (OSA) is by definition a disorder of nighttime breathing however, there is good evidence that impairments in cognitive and cardiovascular function persist in the day and that adults with OSA exhibit daytime CO2 retention and hypoxemia. Although a diagnosis of OSA requires in‐home or in‐laboratory overnight polysomnography, these types of tests are expensive and, due to health insurance quotas, may be limited in availability. Here, we outline simple methods for assessing daytime respiratory sinus arrhythmia (RSA) and respiratory stability that show promise as potential diagnostic tools to identify adults at risk for OSA. We recorded heart rate (finger oxy‐photoplethysmography) and respiration (inductance plethysmography) in adults with obstructive sleep apnea (N=6) and age and BMI matched healthy adults (N=8). Subjects completed five minutes of eupneic breathing, five minutes of paced breathing (7.5 breaths/minute) and after equilibration, five minutes of hyperoxic, hypercapnia (5% FICO2). Using de‐identified data, we obtained estimates of RSA amplitude, RSA stability, and respiratory stability for each subject in each condition and performed a regression analysis to determine the relationship between each of these variables and subjects' apnea hypopnea index (0–25 AHI). Our preliminary results indicate that daytime measures of respiratory stability and RSA can differentiate healthy adults from adults diagnosed with OSA (p&lt;0.006). Importantly, the analysis requires minimal instrumentation and short sampling periods (~5 minutes). Summary schematics arising from the analysis may prove useful as preliminary clinical/diagnostic biomarkers of RSA and cardio‐respiratory coupling in adults at risk for OSA.Support or Funding InformationThis work was supported by start‐up monies (Department of Physiology, University of Arizona) awarded to EFB and by The Finley and Florence Brown Predoctoral Fellowship (Sarver Heart Center, University of Arizona) awarded to JRV.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Increasing heat waves and warm spells in India, observed from a multiaspect framework

AbstractRecent heat waves have been a matter of serious concern for India because of potential impacts on agriculture, food security, and socioeconomic progress. This study examines the trends and variability in frequency, duration, and intensity of hot episodes during three time periods (1951–2013, 1981–2013 and 1998–2013) by defining heat waves based on the percentile of maximum, minimum, and mean temperatures. The study also explores heat waves and their relationships with hydroclimatic variables, such as rainfall, terrestrial water storage, Palmer drought severity index, and sea surface temperature. Results reveal that the number, frequency, and duration of daytime heat waves increased considerably during the post‐1980 dry and hot phase over a large area. The densely populated and agriculturally dominated northern half of India stands out as a key region where the nighttime heat wave metrics reflected the most pronounced amplifications. Despite the recent warming hiatus in India and other parts of the world, we find that both daytime and nighttime extreme measures have undergone substantial changes during or in the year following a dry year since 2002, with the probability distribution functions manifesting a hotter‐than‐normal climate during 1998–2013. This study shows that a few months preceding the 2010 record‐breaking heat wave in Russia, India experienced the largest hot episode in the country's history. Interestingly, both these mega events are comparable in terms of their evolution and amplification. These findings emphasize the importance of planning for strategies in the context of the rising cooccurrence of dry and hot events.

Analysis of nocturnal air temperature in districts using mobile measurements and a cooling indicator

The urban heat island phenomenon is generally defined as an air temperature difference between a city center and the non-urbanized rural areas nearby. However, this description does not encompass the intra-urban temperature differences that exist between neighborhoods in a city. This study investigates the air temperature dynamics of neighborhoods for meteorological conditions that lead to important urban heat island amplitude. Local climate zones (LCZs) have been determined in Nancy, France, and mobile screen-height air temperature measurements are performed using an instrumented vehicle. Initially, hourly measurements are performed within four different LCZs. These results show that air temperature within LCZ demonstrates a nocturnal cooling in two phases, i.e., a first phase between 1 to 3 h before sunset and 3 to 5 h after sunset, and a second phase from 3 to 5 h after sunset to sunrise. During phase 1, neighborhoods exhibit different cooling rate values and air temperature gaps develop between districts, while during phase 2, cooling rates tend to be analogous. Then, a larger meteorological data set is used to investigate these two phases for a selection of 13 LCZs. Normalized cooling rates are calculated between daytime measures and nighttime measures in order to quantify the air temperature dynamics of the studied areas during phase 1. Considering this indicator, three groups are emerging: Results indicate that the relative position of LCZ within the conurbation does not drive air temperature dynamics during phase 1. In addition, measures performed during phase 2 tend to illustrate that cooling rates are similar to all LCZ during this period.

Struggling to Stay Awake: The Sleep Patterns of Adventist Secondary School Students

Sleep deprivation studies indicate that sleep is vital to emotional, physical and behavioural wellbeing. This study presents the results of a survey in which 945 students in Seventh-day Adventist secondary schools responded to questions about the length and quality of their sleep. The study found that: almost one half of the students were at risk of falling short of the recommended number of hours of sleep per night; toward one in every five students were averaging six or fewer hours sleep per night; the quality of sleep (in terms of better sleep habits) and the resulting levels of daytime alertness were clearly linked to having a permanent, personal space for sleep; and finally that academic performance was strongly related to measures of daytime alertness and measures of the quality of sleep habits.

In search of objective components for sleep quality indexing in normal sleep

The main goal of this study was to investigate to what extent polysomnographic (PSG) recordings of nocturnal human sleep can provide information about sleep quality in terms of correlation with a set of daytime measures. These measures were designed with the aim of comprising selected quality of night sleep and consist of subjective sleep quality ratings, neuropsychological tests and physiological parameters. First, a factor analysis model was applied to the large number of daytime measures of sleep quality in order to detect their latent structure. Secondly, in addition to the gold standard sleep staging method to arrive at variables about sleep architecture from PSG, we applied a recently developed continuous sleep representation by considering the probabilistic sleep model (PSM) describing the microstructure of sleep. Significant correlations between sleep architecture and daytime variables of sleep quality were found. Both the factor analysis and the PSM helped maximize the information about this relationship.