The effect of hyperoxia on muscle sympathetic nerve activity: a systematic review and meta-analysis.

PURPOSE: We conducted a meta-analysis to determine the effect of hyperoxia on muscle sympathetic nerve activity in healthy individuals and those with cardio-metabolic diseases. METHODS: A comprehensive search of electronic databases was performed until August 2022. All study designs (except reviews) were included: population (humans; apparently healthy or with at least one chronic disease); exposures (muscle sympathetic nerve activity during hyperoxia or hyperbaria); comparators (hyperoxia or hyperbaria vs. normoxia); and outcomes (muscle sympathetic nerve activity, heart rate, blood pressure, minute ventilation). Forty-nine studies were ultimately included in the meta-analysis. RESULTS: In healthy individuals, hyperoxia had no effect on sympathetic burst frequency (mean difference [MD] - 1.07 bursts/min; 95% confidence interval [CI] - 2.17, 0.04bursts/min; P = 0.06), burst incidence (MD 0.27 bursts/100 heartbeats [hb]; 95% CI - 2.10, 2.64 bursts/100 hb; P = 0.82), burst amplitude (P = 0.85), or total activity (P = 0.31). In those with chronic diseases, hyperoxia decreased burst frequency (MD - 5.57 bursts/min; 95% CI - 7.48, - 3.67 bursts/min; P < 0.001) and burst incidence (MD - 4.44 bursts/100 hb; 95% CI - 7.94, - 0.94 bursts/100 hb; P = 0.01), but had no effect on burst amplitude (P = 0.36) or total activity (P = 0.90). Our meta-regression analyses identified an inverse relationship between normoxic burst frequency and change in burst frequency with hyperoxia. In both groups, hyperoxia decreased heart rate but had no effect on any measure of blood pressure. CONCLUSION: Hyperoxia does not change sympathetic activity in healthy humans. Conversely, in those with chronic diseases, hyperoxia decreases sympathetic activity. Regardless of disease status, resting sympathetic burst frequency predicts the degree of change in burst frequency, with larger decreases for those with higher resting activity.

The effect of hypoxemia on muscle sympathetic nerve activity and cardiovascular function: a systematic review and meta-analysis.

We conducted a systematic review and meta-analysis to determine the effect of acute poikilocapnic, high-altitude, and acute isocapnia hypoxemia on muscle sympathetic nerve activity (MSNA) and cardiovascular function. A comprehensive search across electronic databases was performed until June 2021. All observational designs were included: population (healthy individuals); exposures (MSNA during hypoxemia); comparators (hypoxemia severity and duration); outcomes (MSNA; heart rate, HR; and mean arterial pressure, MAP). Sixty-one studies were included in the meta-analysis. MSNA burst frequency increased by a greater extent during high-altitude hypoxemia [P < 0.001; mean difference (MD), +22.5 bursts/min; confidence interval (CI) = -19.20 to 25.84] compared with acute poikilocapnic hypoxemia (P < 0.001; MD, +5.63 bursts/min; CI = -4.09 to 7.17) and isocapnic hypoxemia (P < 0.001; MD, +4.72 bursts/min; CI = -3.37 to 6.07). MSNA burst amplitude was only elevated during acute isocapnic hypoxemia (P = 0.03; standard MD, +0.46 au; CI = -0.03 to 0.90), and MSNA burst incidence was only elevated during high-altitude hypoxemia [P < 0.001; MD, 33.05 bursts/100 heartbeats; CI = -28.59 to 37.51]. Meta-regression analysis indicated a strong relationship between MSNA burst frequency and hypoxemia severity for acute isocapnic studies (P < 0.001) but not acute poikilocapnia (P = 0.098). HR increased by the same extent across each type of hypoxemia [P < 0.001; MD +13.81 heartbeats/min; 95% CI = 12.59-15.03]. MAP increased during high-altitude hypoxemia (P < 0.001; MD, +5.06 mmHg; CI = 3.14-6.99), and acute isocapnic hypoxemia (P < 0.001; MD, +1.91 mmHg; CI = 0.84-2.97), but not during acute poikilocapnic hypoxemia (P = 0.95). Both hypoxemia type and severity influenced sympathetic nerve and cardiovascular function. These data are important for the better understanding of healthy human adaptation to hypoxemia.

Muscle sympathetic nerve activity during pregnancy: A systematic review and meta-analysis.

We conducted a systematic review and meta-analysis to quantify the impact of healthy and complex pregnancy on muscle sympathetic nerve activity (MSNA) at rest, and in response to stress. Structured searches of electronic databases were performed until February 23, 2022. All study designs (except reviews) were included: population (pregnant individuals); exposures (healthy and complicated pregnancy with direct measures of MSNA); comparator (individuals who were not pregnant, or with uncomplicated pregnancy); and outcomes (MSNA, BP, and heart rate). Twenty-seven studies (N = 807) were included. MSNA burst frequency was higher in pregnancy (n = 201) versus non-pregnant controls (n = 194) (Mean Differences [MD], MD: 10.6 bursts/min; 95% CI: 7.2, 14.0; I2  = 72%). Accounting for the normative increase in heart rate with gestation, burst incidence was also higher during pregnancy (Pregnant N = 189, non-pregnant N = 173; MD: 11 bpm; 95% CI: 8, 13 bpm; I2  = 47%; p < 0.0001). Meta-regression analyses confirmed that although sympathetic burst frequency and incidence are augmented during pregnancy, this was not significantly associated with gestational age. Compared to uncomplicated pregnancy, individuals with obesity, obstructive sleep apnea, and gestational hypertension exhibited sympathetic hyperactivity, while individuals with gestational diabetes mellitus or preeclampsia did not. Uncomplicated pregnancies exhibited a lesser response to head-up tilt, but an exaggerated sympathetic responsiveness to cold pressor stress compared to non-pregnant individuals. MSNA is higher in pregnant individuals and further increased with some, but not all pregnancy complications. PROSPERO registration number: CRD42022311590.

A complicated Glenn procedure: risk factors and association with adverse long-term neurodevelopmental and functional outcomes.

OBJECTIVES: To determine potentially modifiable risk factors for a complicated Glenn procedure (cGP) and whether a cGP predicted adverse neurodevelopmental and functional outcomes. A cGP was defined as post-operative death, heart transplant, extracorporeal life support, Glenn takedown, or prolonged ventilation. METHODS: All 169 patients having a Glenn procedure from 2012 to 2017 were included. Neurodevelopmental assessments were performed at age 2 years in consenting survivors (n = 156/159 survivors). The Bayley Scales of Infant and Toddler Development-3rd Edition (Bayley-III) and the Adaptive Behavior Assessment System-2nd Edition (ABAS-II) were administered. Adaptive functional outcomes were determined by the General Adaptive Composite (GAC) score from the ABAS-II. Predictors of outcomes were determined using univariate and multiple variable linear or Cox regressions. RESULTS: Of patients who had a Glenn procedure, 10/169 (6%) died by 2 years of age and 27/169 (16%) had a cGP. Variables statistically significantly associated with a cGP were the inotrope score on post-operative day 1 (HR 1.04, 95%CI 1.01, 1.06; p = 0.010) and use of inhaled nitric oxide post-operatively (HR 7.31, 95%CI 3.19, 16.76; p < 0.001). A cGP was independently statistically significantly associated with adverse Bayley-III Cognitive (ES -10.60, 95%CI -17.09, -4.11; p = 0.002) and Language (ES -11.43, 95%CI -19.25, -3.60; p = 0.004) scores and adverse GAC score (ES -14.89, 95%CI -22.86, -6.92; p < 0.001). CONCLUSIONS: Higher inotrope score and inhaled nitric oxide used post-operatively were associated with a cGP. A cGP was independently associated with adverse 2-year neurodevelopmental and functional outcomes. Whether early recognition and intervention for risk of a cGP can prevent adverse outcomes warrants study.

Emergency Department Visits During Pregnancy.

STUDY OBJECTIVE: Pregnant women often seek care in an emergency department (ED). We sought to describe the frequency, characteristics, and factors associated with increased ED visits during pregnancy. METHODS: We conducted a retrospective cohort study using administrative health data of all pregnancies resulting in a live birth at 20 or more weeks of gestation in Alberta, Canada, from 2011 to 2017. The primary outcome was the occurrence of any ED visit during pregnancy. The secondary outcomes were ED visit characteristics and discharge disposition. We calculated rate ratios (RRs) and 95% confidence intervals (CIs) for associations between sociodemographic and clinical factors and increased ED visits during pregnancy using random-effect negative binomial regression adjusting for multiple pregnancies per person during the study period. RESULTS: We included 255,929 pregnancies from 193,965 women. Of all the pregnancy episodes followed, 37.3% (95% CI 37.1 to 37.5) had at least 1 ED visit, resulting in a total of 226,811 ED visits and an overall ED visit rate of 94.0 visits per 100 pregnancies (95% CI 93.6 to 94.3). Most visits were nonobstetric (46.4%) and resulted in ED discharge (85.3%). Increased ED visits were associated with living in remote (RR 6.9; 95 %CI 6.7 to 7.1) or rural (RR 3.4; 95% CI 3.4 to 3.5) areas, younger age (RR 1.9; 95% CI 1.8 to 2.0), intensive prenatal care (RR 1.5; 95% CI 1.5 to 1.5), major/moderate health conditions (RR 1.6; 95% CI 1.6 to 1.6), mental health conditions (RR 1.6; 95% CI 1.5 to 1.6), and high antepartum risk score (RR 1.1; 95% CI 1.1 to 1.1). CONCLUSION: Approximately 1 in 3 women in our sample visited the ED during pregnancy. A higher number of visits occurred in those with rural/remote residence, younger maternal age, and concomitant health conditions.

Associations between demographic and parental factors and infant sleep characteristics.

Although sleep problems are highly prevalent in infants, the intrinsic and extrinsic factors that influence sleep consolidation and regulation in this age group are not well understood. This study aimed to examine the cross-sectional associations of demographic and parental factors with infant sleep characteristics. Participants were 97 Canadian mother-infant dyads primarily from Edmonton, Alberta. Demographic factors (e.g., infant age), parenting practices (e.g., sleep position, sleep initiation methods), and infants sleep characteristics (e.g., the frequency of nighttime awakenings) were assessed using the Brief Infant Sleep Questionnaire. Maternal sleep characteristics (e.g., nighttime sleep duration) were assessed using Actigraph accelerometers. Infant age (mean = 4.24 ± 2.90) was associated with most infant sleep characteristics. In multiple regression models for infant nighttime sleep duration, after removing influential observations, a negative association for side (vs. prone) sleep position was, respectively, observed. In multiple regression models for the frequency of nighttime awakenings in infants, positive associations for infants falling asleep while feeding (vs. in bed alone) and side (vs. prone) sleep position were consistently observed after removing influential observations. Lower nighttime sleep efficiency (B = - 0.08, 95%CI: - 0.13, - 0.02) and longer nighttime wake after sleep onset (B = 1.03, 95%CI: 0.41, 1.65) in mothers were associated with more frequent nighttime awakenings in infants. After removing influential observations, more frequent nighttime awakenings (B = 0.35; 95%CI: 0.09, 0.61) and longer total sleep duration (B = 0.33, 95%CI: 0.11, 0.55) in mothers were also associated with more frequent nighttime awakenings in infants. Sleep initiation methods with less parental involvement, and more continuous and efficient maternal nighttime sleep, tended to be associated with less interrupted infant sleep.

Influence of Obstructive Sleep Apnea Severity on Muscle Sympathetic Nerve Activity and Blood Pressure: a Systematic Review and Meta-Analysis.

BACKGROUND: We conducted meta-analyses to identify relationships between obstructive sleep apnea (OSA) severity, muscle sympathetic nerve activity (MSNA), and blood pressure (BP). We quantified the effect of OSA treatment on MSNA. METHODS: Structured searches of electronic databases were performed until June 2021. All observational designs (except reviews) were included: population (individuals with OSA); exposures (OSA diagnosis and direct measures of MSNA); comparator (individuals without OSA or different severity of OSA); outcomes (MSNA, BP, and heart rate). RESULTS: Fifty-six studies (N=1872) were included. MSNA burst frequency was higher in OSA (27 studies; n=542) versus controls (n=488; mean differences [MDs], +15.95 bursts/min [95% CI, 12.6-17.6 bursts/min]; I2=86%). As was burst incidence (20 studies; n=357 OSA, n=312 Controls; MD, +22.23 bursts/100 hbs [95% CI, 18.49-25.97 bursts/100 hbs]; I2=67%). Meta-regressions indicated relationships between MSNA and OSA severity (burst frequency, R2=0.489; P<0.001; burst incidence, R2=0.573; P<0.001). MSNA burst frequency was related to systolic pressure (R2=0.308; P=0.016). OSA treatment with continuous positive airway pressure reduced MSNA burst frequency (MD, 11.91 bursts/min [95% CI, 9.36-14.47 bursts/min] I2=15%) and systolic (n=49; MD, 10.3 mm Hg [95% CI, 3.5-17.2 mm Hg]; I2=42%) and diastolic (MD, 6.9 mm Hg [95% CI, 2.3-11.6 mm Hg]; I2=37%) BP. CONCLUSIONS: MSNA is higher in individuals with OSA and related to severity. This sympathoexcitation is also related to BP in patients with OSA. Treatment effectively reduces MSNA and BP, but limited data prevents an assessment of the link between these reductions. These data are clinically important for understanding cardiovascular disease risk in patients with OSA. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: CRD42021285159.

TV time, physical activity, sedentary behaviour and cardiometabolic biomarkers in pregnancy-NHANES 2003-2006.

OBJECTIVES: This study examined the impacts of individual and combined associations between moderate-to-vigorous physical activity (MVPA) and sedentary time (ST) (accelerometer-derived), as well as MVPA and television (TV) time (self-reported) on cardiometabolic biomarkers during pregnancy. METHODS: Participants were 332 pregnant women from the 2003-2006 cycles of the National Health and Nutrition Examination Survey (NHANES). Multiple linear regression models were conducted to examine the relationships between individual and combinations of high/low MVPA, ST, and TV time with cardiometabolic biomarkers: body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), high-density lipoprotein cholesterol (HDL), and C-reactive protein (CRP). RESULTS: Women with high MVPA (≥ 17 min/day) compared to those with low MVPA (< 17 min/day) had significantly lower BMI. Women with low ST (< 503 min/day) compared to those with high ST (≥ 503 min/day) had significantly lower SBP and DBP. Women with low TV (< 3 h/day) compared to those with high TV (≥ 3 h/day) had significantly lower BMI and log-transformed CRP. Women with a combination of low ST/high MVPA had lower SBP and DBP (ptrend < 0.03). Women with a combination of low TV/high MVPA had lower BMI and log-transformed CRP (ptrend < 0.00). CONCLUSION: We need to consider both physical activity and sedentary time for improved cardiometabolic health during pregnancy.

RéSUMé: OBJECTIFS: Notre étude porte sur les effets des associations individuelles et combinées entre l'activité physique modérée à vigoureuse (APMV) et le temps de sédentarité (TS) (mesuré par accéléromètre), ainsi qu'entre l'APMV et le temps de télévision (TT) (autodéclaré) et les biomarqueurs cardiométaboliques durant la grossesse. MéTHODE: Les participantes étaient 332 femmes enceintes ayant participé aux cycles 2003­2006 de la National Health and Nutrition Examination Survey (NHANES). Des modèles de régression linéaire multiple ont été appliqués aux liens individuels et combinés entre l'APMV, le TS et le TT élevés/faibles et les biomarqueurs cardiométaboliques suivants : indice de masse corporelle (IMC), pression systolique (PS), pression diastolique (PD), cholestérol à lipoprotéines de haute densité (HDL) et protéine C réactive (CRP). RéSULTATS: L'IMC était significativement plus faible chez les femmes dont l'APMV était élevée (≥ 17 min/j) que chez celles dont l'APMV était faible (< 17 min/j). La PS et la PD étaient significativement plus faibles chez les femmes dont le TS était faible (< 503 min/j) que chez celles dont le TS était élevé (≥ 503 min/j). L'IMC et la protéine CRP log-transformée étaient significativement plus faibles chez les femmes dont le TT était faible (< 3 h/j) que chez celles dont le TT était élevé (≥ 3 h/j). La PS et la PD étaient plus faibles (ptendance < 0,03) chez les femmes qui présentaient une combinaison de TS faible et d'APMV élevée. Et l'IMC et la protéine CRP log-transformée étaient plus faibles (ptendance < 0,00) chez les femmes qui présentaient une combinaison de TT faible et d'APMV élevée. CONCLUSION: Il faut tenir compte à la fois de l'activité physique et du temps de sédentarité pour améliorer la santé cardiométabolique durant la grossesse.

Emergency Department Visits During the Postpartum Period: A Canadian Cohort Study.

STUDY OBJECTIVE: Challenges in transitioning from obstetric to primary care in the postpartum period may increase emergency department (ED) visits. This study described the frequency, characteristics, and predictors of maternal ED visits in the postpartum period. METHODS: Retrospective cohort study of all live-birth pregnancies occurring in Alberta (Canada) between 2011 and 2017. Individual-level health and ED utilization data was linked across 5 population health databases. We calculated age-standardized ED visit rates in the postpartum period and used negative binomial regression models to assess the outcome of any ED visit in the postpartum period associated with relevant sociodemographic and clinical factors. Results were reported using rate ratios (RRs) and 95% confidence intervals (95% CIs). RESULTS: Data on 255,929 pregnancies from 193,965 individuals were analyzed. During the study period, 44.7% of pregnancies had 1 or more ED visits; 29.7% of visits occurred within 6 weeks after delivery. Increased postpartum ED visits were associated with living in remote (RR, 2.8; 95% CI, 2.6 to 2.9) or rural areas (RR, 2.3; 95% CI, 2.3 to 2.4), age less than 20 years (RR, 2.5; 95% CI, 2.4 to 2.6), mental (RR, 1.6; 95% CI, 1.6 to 1.7) and major/moderate health conditions (RR, 1.5; 95% CI, 1.5 to 1.6), multiparity 4 or more (RR, 2.0; 95% CI, 1.9 to 2.1), cesarean delivery (RR, 1.4; 95% CI, 1.4 to 1.4), and intensive prenatal care (RR, 1.4; 95% CI, 1.4 to 1.5). CONCLUSION: Almost one third of ED visits in the postpartum occurred within 6 weeks immediately after delivery. Potential gaps in equitable access and quality of prenatal care should be bridged by appropriate transitions to primary care in the postpartum period.

The effects of physical activity on arterial stiffness during pregnancy: an observational study.

The objective of the present study was to investigate the relationship between moderate-to-vigorous physical activity (MVPA) and arterial stiffness in pregnancy. Thirty-nine women participated in this study, resulting in 68 measurements in non-pregnant (NP; n = 21), first (TM1; n = 8), second (TM2; n = 20), and third trimesters (TM3; n = 19). Compliance, distensibility, elasticity, ß-stiffness, and carotid to femoral (central) and carotid to finger (peripheral) pulse wave velocity (PWV) were assessed. MVPA was measured using accelerometry. Multilevel linear regressions adjusted for multiple tests per participant using random effects to generate ß coefficients and 95% confidence intervals (CIs) were performed. Distensibility, elasticity, ß-stiffness, and central- and peripheral-PWV did not differ between pregnant and non-pregnant assessments. Carotid artery compliance was higher in TM2 compared with NP. Central PWV (ß coefficient: -0.14, 95% CI: -0.27, -0.02) decreased from early to mid-pregnancy and increased in late pregnancy. Meeting the MVPA guidelines was significantly associated with central-PWV (adjusted ß coefficient: -0.34, 95% CI: -0.62, -0.06, p = 0.016), peripheral-PWV (adjusted ß coefficient: -0.54, 95% CI: -0.91, -0.16, p = 0.005), and distensibility (adjusted ß coefficient: -0.001, 95% CI: -0.002, -0.0001, p = 0.018), in pregnancy. These results suggest that MVPA may be associated with improved (i.e., reduced) arterial stiffness in pregnancy. Novelty: Central PWV, distensibility, compliance, elasticity, and ß-stiffness, but not peripheral PWV, exhibited curvilinear relationships with gestational age Central and peripheral PWV were lower in pregnant women who met the physical activity guidelines of 150 minutes of moderate-to-vigorous physical activity per week.

The influence of sleep quality on weight retention in the postpartum period.

Poor sleep in the postpartum is often treated as an unavoidable consequence of childbirth. This study aims to compare objective and subjective measures of sleep, explore the relationship between sleep and postpartum weight retention (PPWR), and investigate factors that may contribute to sleep quality in the postpartum period. In this cross-sectional cohort, PPWR, sleep quality (Pittsburgh Sleep Quality Index (PSQI)), and objective sleep and physical activity (accelerometry) were assessed in 109 women 0-52 weeks postpartum. Anthropometric and demographic data were collected. Gestational weight gain (GWG) was classified as inadequate, appropriate, or excessive according to Institute of Medicine guidelines. Average GWG (33.7 lbs) and PPWR (5.39 lbs) were not different between "good" (PSQI < 6) and "bad" (PSQI ≥ 6) sleepers. Following adjustment, mothers with excessive GWG who were "bad" sleepers had 5.26 higher odds of PPWR ≥ 10 lbs compared with all other combinations of GWG and PSQI. PSQI was not correlated with total sleep time (accelerometer-derived). Light activity and moderate-to-vigorous physical activity (MVPA) were associated with reduced odds of being a "bad" sleeper. The influence of GWG on PPWR was modified by postpartum sleep quality. Both light activity and meeting the MVPA guidelines in the postpartum were associated with higher sleep quality. Novelty Subjectively rated poor sleep may represent the number of awakenings and wake after sleep onset in postpartum women. Poor postpartum sleep quality increases excessive postpartum weight retention in women with excessive GWG. Women doing light-to-vigorous physical activity in the postpartum are less likely to experience poor sleep quality.

Sleep, circadian rhythm, and gut microbiota.

From asthma and heart disease to diabetes and obesity, the human microbiome plays a role in the pathogenesis of each chronic health condition plaguing today's society. Recent work has shown that the gut microbiota and its metabolites exhibit diurnal rhythmicity which predominantly respond to the feeding/fasting cycle. Persistent jet lag, an obesogenic diet, and clock gene deficiency can dampen the oscillatory nature of gut bacterial composition, which can subsequently be rescued by time restricted feeding. Contrastingly, gut microbial metabolites influence central and hepatic clock gene expression and sleep duration in the host and regulate body composition through circadian transcription factors. Both sleep fragmentation and short sleep duration are associated with gut dysbiosis which may be due to activation of the HPA-axis. Metabolic disturbances associated with sleep loss may in fact be mediated through the overgrowth of specific gut bacteria. Reciprocally, the end products of bacterial species which grow in response to sleep loss are able to induce fatigue. Furthermore, probiotic supplementation has been found to improve subjective sleep quality. Sleep quality and duration may be an important target for supporting healthy gut microbiota composition, but the cyclic nature of this relationship should not be overlooked.

Longitudinal study of cerebral blood flow regulation during exercise in pregnancy.

Cerebrovascular adaptation to pregnancy is poorly understood. We sought to assess cerebrovascular regulation in response to visual stimulation, hypercapnia and exercise across the three trimesters of pregnancy. Using transcranial Doppler (TCD) ultrasound, middle and posterior cerebral artery mean blood velocities (MCAvmean and PCAvmean) were measured continuously at rest and in response to (1) visual stimulation to assess neurovascular coupling (NVC); (2) a modified Duffin hyperoxic CO2 rebreathe test, and (3) an incremental cycling exercise test to volitional fatigue in non-pregnant (n = 26; NP) and pregnant women (first trimester [n = 13; TM1], second trimester [n = 21; TM2], and third trimester [n = 20; TM3]) in total 47 women. At rest, MCAvmean and PETCO2 were lower in TM2 compared to NP. PCAvmean was lower in TM2 but not TM1 or TM3 compared to NP. Cerebrovascular reactivity in MCAvmean and PCAvmean during the hypercapnic rebreathing test was not different between pregnant and non-pregnant women. MCAvmean continued to increase over the second half of the exercise test in TM2 and TM3, while it decreased in NP due to differences in ΔPETCO2 between groups. Pregnant women experienced a delayed decrease in MCAvmean in response to maximal exercise compared to non-pregnant controls which was explained by CO2 reactivity and PETCO2 level.

Prenatal depression and birth mode sequentially mediate maternal education's influence on infant sleep duration.

RATIONALE: Sleep duration is critical to growth, learning, and immune function development in infancy. Strategies to ensure that national recommendations for sleep duration in infants are met require knowledge of perinatal factors that affect infant sleep. OBJECTIVES: To investigate the mechanistic pathways linking maternal education and infant sleep. METHODS: An observational study was conducted on 619 infants whose mothers were enrolled at the Edmonton site of the CHILD birth cohort. Infant sleep duration at three months was assessed using the Brief Infant Sleep Questionnaire. Maternal education was collected via maternal report. Prenatal and postnatal depression scores were obtained from the 20-item Center for Epidemiologic Studies Depression Scale (CES-D). Birth records and maternal report were the source of covariate measures. Mediation analysis (PROCESS v3.0) was used to examine the indirect effects of maternal education on infant sleep duration mediated through prenatal depression and birth mode. MEASUREMENTS AND MAIN RESULTS: At three months of age, infants slept on average 14.1 h. Lower maternal education and prenatal depression were associated with significantly shorter infant sleep duration. Emergency cesarean section birth was associated with 1-hour shorter sleep duration at three months compared to vaginal birth [without intrapartum antibiotic prophylaxis] (ß: -0.99 h; 95% CI: -1.51, -0.48). Thirty percent of the effect of lower maternal education on infant total sleep duration was mediated sequentially through prenatal depression and birth mode (Total Indirect Effects: -0.12, 95% CI: -0.22, -0.03, p < 0.05). CONCLUSIONS: Prenatal depression and birth mode sequentially mediate the effect of maternal education on infant sleep duration.

Peripheral chemoreceptor deactivation attenuates the sympathetic response to glucose ingestion.

Acute increases in blood glucose are associated with heightened muscle sympathetic nerve activity (MSNA). Animal studies have implicated a role for peripheral chemoreceptors in this response, but this has not been examined in humans. Heart rate, cardiac output (CO), mean arterial pressure, total peripheral conductance, and blood glucose concentrations were collected in 11 participants. MSNA was recorded in a subset of 5 participants via microneurography. Participants came to the lab on 2 separate days (i.e., 1 control and 1 experimental day). On both days, participants ingested 75 g of glucose following baseline measurements. On the experimental day, participants breathed 100% oxygen for 3 min at baseline and again at 20, 40, and 60 min after glucose ingestion to deactivate peripheral chemoreceptors. Supplemental oxygen was not given to participants on the control day. There was a main effect of time on blood glucose (P < 0.001), heart rate (P < 0.001), CO (P < 0.001), sympathetic burst frequency (P < 0.001), burst incidence (P = 0.01), and total MSNA (P = 0.001) for both days. Blood glucose concentrations and burst frequency were positively correlated on the control day (r = 0.42; P = 0.03) and experimental day (r = 0.62; P = 0.003). There was a time × condition interaction (i.e., normoxia vs. hyperoxia) on burst frequency, in which hyperoxia significantly blunted burst frequency at 20 and 60 min after glucose ingestion only. Given that hyperoxia blunted burst frequency only during hyperglycemia, our results suggest that the peripheral chemoreceptors are involved in activating MSNA after glucose ingestion.

Extreme pregnancy: maternal physical activity at Everest Base Camp.

High-altitude natives employ numerous physiological strategies to survive and reproduce. However, the concomitant influence of altitude and physical activity during pregnancy has not been studied above 3,700 m. We report a case of physical activity, sleep behavior, and physiological measurements on a 28-yr-old third-trimester pregnant native highlander (Sherpa) during ascent from 3,440 m to Everest Base Camp (~5,300 m) over 8 days in the Nepal Himalaya and again ~10 mo postpartum during a similar ascent profile. The participant engaged in 250-300 min of moderate to vigorous physical activity per day during ascent to altitude while pregnant, with similar volumes of moderate to vigorous physical activity while postpartum. There were no apparent maternal, fetal, or neonatal complications related to the superimposition of the large volumes of physical activity at altitude. This report demonstrates a rare description of physical activity and ascent to high altitude during pregnancy and points to novel questions regarding the superimposition of pregnancy, altitude, and physical activity in high-altitude natives.

Sympathetic baroreflex gain in normotensive pregnant women.

Muscle sympathetic nerve activity is increased during normotensive pregnancy while mean arterial pressure is maintained or reduced, suggesting baroreflex resetting. We hypothesized spontaneous sympathetic baroreflex gain would be reduced in normotensive pregnant women relative to nonpregnant matched controls. Integrated muscle sympathetic burst incidence and total sympathetic activity (microneurography), blood pressure (Finometer), and R-R interval (ECG) were assessed at rest in 11 pregnant women (33 ± 1 wk gestation, 31 ± 1 yr, prepregnancy BMI: 23.5 ± 0.9 kg/m(2)) and 11 nonpregnant controls (29 ± 1 yr; BMI: 25.2 ± 1.7 kg/m(2)). Pregnant women had elevated baseline sympathetic burst incidence (43 ± 2 vs. 33 ± 2 bursts/100 heart beats, P = 0.01) and total sympathetic activity (1,811 ± 148 vs. 1,140 ± 55 au, P < 0.01) relative to controls. Both mean (88 ± 3 vs. 91 ± 2 mmHg, P = 0.4) and diastolic (DBP) (72 ± 3 vs. 73 ± 2 mmHg, P = 0.7) pressures were similar between pregnant and nonpregnant women, respectively, indicating an upward resetting of the baroreflex set point with pregnancy. Baroreflex gain, calculated as the linear relationship between sympathetic burst incidence and DBP, was reduced in pregnant women relative to controls (-3.7 ± 0.5 vs. -5.4 ± 0.5 bursts·100 heart beats(-1)·mmHg(-1), P = 0.03), as was baroreflex gain calculated with total sympathetic activity (-294 ± 24 vs. -210 ± 24 au·100 heart beats(-1)·mmHg(-1); P = 0.03). Cardiovagal baroreflex gain (sequence method) was not different between nonpregnant controls and pregnant women (49 ± 8 vs. 36 ± 8 ms/mmHg; P = 0.2). However, sympathetic (burst incidence) and cardiovagal gains were negatively correlated in pregnant women (R = -0.7; P = 0.02). Together, these data indicate that the influence of the sympathetic nervous system over arterial blood pressure is reduced in normotensive pregnancy, in terms of both long-term and beat-to-beat regulation of arterial pressure, likely through a baroreceptor-dependent mechanism.