Poster group
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poster
Group child care has become normative in the United States. Day care can be challenging for infants, who must negotiate separations from attachment figures.These challenges place demands on adaptive systems including the physiological systems involved in stress management. The hypothalamic-pituitary-adrenocortical(HPA) system has been implicated in social adaptation. The HPA system produces the hormone cortisol, which can be measured in saliva. Cortisol levels in humansfollow a daily rhythm, rising in the morning and falling throughout the afternoon. Chronically high cortisol may have implications for immune system functioning and the developing central nervous system. Previous studies of cortisol-behavior relations of toddlers and preschoolers show an atypical rise in cortisol in the afternoon in daycare but not at home. However, little is known about infants in daycare. The purpose of the present study was three-fold:(a) to enhance existing knowledge of the developing HPA system in infancy (b) toexamine daily patterns of cortisol levels in infants in day care compared to cortisol patterns at home (c) to examine the relationship between child temperament, cortisol reactivity, quality of child care facility, and the infant's affect, activity level, engagement in play, distress level, and felt security at day care.Twenty-five normally developing infants were recruited fromfour child care centers in a large midwestern city. Two of the centers were affiliated with major universities. The other two centers were YMCA facilities in lower working class areas. Infants ranged in age from three months to 18 months, with a mean age of ten months. Salivary cortisol was sampled in the morning and in the afternoon on two different days at the center and again at home. The saliva was collected by having the children mouth cotton dental rolls dipped in a few grains of dry presweetened Kool-aid*. This author and a lab research associate observed infants in the morning and again in the afternoon, coding the infants' affect, activity level, distress level, involvement in play,interactions with others, and response to soothing. Kappas ranged from .80 to 97. Teachers and parents each completed a temperament questionnaire, and information was obtained about each child's attachment relationship(s) at the daycare. Mean cortisol levels at day care will be compared with mean cortisol levels at home. Hierarchical regression analyses will be performed with temperament, affect, and play behavior composites as blocks representing easy and difficult behavioral styles, and morning and afternoon cortisol values as the criterion. It is expected that, overall, infants will show a normative pattern of cortisolsecretion both in day care and at home, with higher cortisol in the morning and decreasing levels of cortisol during the afternoon. Infants with more challenging behavior styles, i.e. a more difficult temperament, who are in a lower quality child care setting will have higher cortisol levels in the afternoon while at day care.
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Past work has shown that infants reared in orphanages exhibit physical growth and behavioral delays (Rutter et al., 1998). Some children rapidly return to normal developmental trajectories, while others continue to exhibit marked delays (Ames, 1997). Often, physical growth retardation and cognitive delays at adoption do not strongly predict later recovery (Rutter et al., 1998). In addition, several studies have shown that institutional rearing alters the activity of stress-sensitive physiological systems, in particular the hypothalamic-pituitary-adrenocortical (HPA) system (Carlson & Earls, 1997; Gunnar, in press). In the orphanage, the daily rhythm of cortisol appears blunted, while at six years post-adoption, children exhibited elevated cortisol levels across the day. In the present study, we attempted to determine whether alterations in HPA activity might serve as a more sensitive index of the impact of institutionalization and would be more predictive of cognitive functioning several months after adoption, than would physical growth measures. Participants included 25 children adopted into the United States, between the ages of four and eighteen months, from orphanages primarily in Russia and China. Children were matched on age and sex to Minnesotan children reared in their families of origin. The children were assessed at two and eight months post-adoption. Physical growth measures were obtained at both assessments, two days of home salivary cortisol were obtained at wake-up, mid-morning, mid-afternoon, and bedtime at the first assessment, and the Bayley Scales of Infant Development were administered at the second assessment. Using appropriate international norms, we found post-institutionalized children to be growth delayed in length (mean Z -.93, SD 1.19), weight (mean Z -.80, SD .84), and head circumference (mean Z -.84, SD .83) two months following adoption. Growth measures improved between two and eight months post-adoption, such that by eight months, length and weight were less than a half-standard deviation below the mean. Analyses also indicate that the post-institutionalized children exhibited significant cognitive (M 86.36, SD 14.48) and motor (M 86.92, SD 14.86) delays eight months following adoption.As in the Romanian institutionalized children studied by Carlson and Earls (1997), the post-institutionalized children in the current study also exhibited a blunting in the daily rhythm of cortisol production relative to family-reared children, F(3, 21) 2.99, p .05. Physical growth delays within two months of adoption were not significantly correlated with Bayley scores, when controlling for age (partial r's ranged from -.11 to .15). With the exception of one relatively high-functioning child, blunting of the daily cortisol pattern was significantly related to cognitive functioning as assessed by the Bayley (r -.54, p .058). Surprisingly, the most delayed children exhibited the least blunting in cortisol production, suggesting that dampened activity of the HPA system might have served to protect cognitive development.
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In both the preterm and fullterm neonate, the heart rate (HR) and respiratory rate (RR) are continually varying. Rhythmic components of HR variability (HRV) and RR variability (RRV) generated by the cardiorespiratory circuitry and autonomic nervous system (ANS) may provide important information as to disturbances in the homeostasis of the high-risk neonate. Earlier recognition of risk will lead to improved plans of care, decreased sequelae and morbidity, shortened lengths of stay and justifiable health care expenditures. We investigated the influence of maturation on RR variability (RRV) in 26 spontaneously breathing healthy preterm neonates at 32 weeks post-conceptional age (PCA) and 38 full-term healthy neonates at 38-40 weeks gestational age on the second day of life by evaluating the subject's natural resting breathing using the Alan variance. Informed consent was obtained and the electrocardiograph leads were gently placed in the standard position on a sleeping neonate. After ensuring the neonate was again asleep, the HR and RR were collected for 15 minutes, digitized at 500 samples per second and uploaded to a bedside computer. The Minilogger recorded time intervals between successive breaths. If t(i) is the time between breath i and breath i+1 for a given neonate, then the instantaneous rate of that interval is defined to be its reciprocal, while the mean rate is the number of intervals divided by the total time of measurement. RRV is often quantified by the standard deviation [L. Brochard, Breathing: Does regular mean normal?, Crit. Care Med. 26 (1998), 1773-1774], but that statistic is unreliable for data that is either nonstationary or fractal, situations in which the Allan variance is a good estimator of variability [D. B. Percival and P. Guttorp, In: Wavelets in Geophysics, edited by E. Foufoula-Georgiou and P. Kumar, 325 (Academic Press, New York, 1994)]. It is well-known that physiological variables such as RR often are nonstationary and RR also has fractal properties [Szeto HH, Cheng PY, Decena JA, Wu DL, Cheng Y, and Dwyer D, Fractal properties in fetal breathing dynamics, Am. J. Physiol. 263 (1992), R141-R147], so the Allan variance is a better measure of RRV than the standard deviation. The Allan variance of N instantaneous rates at a scale of k intervals is estimated by the estimator used by [D. B. Percival and P. Guttorp, In: Wavelets in Geophysics, edited by E. Foufoula-Georgiou and P. Kumar, 325 (Academic Press, New York, 1994)]. This quantity has units of breaths/min^2; RRV can be expressed in units of breaths/min by defining an Allan deviation, a(k), as the square root of the Allan variance. We computed a(1), a(2), a(4), a(8), a(16), and a(32) for each of the 26 preterm and 38 fullterm neonates and found that a(4) gives the best separation between the two groups, with more RRV in the preterm group. The difference in RRV between the two groups can be seen by comparing the most typical preterm series with the most typical fullterm series; the high point at the beginning of the first series elevates its value of a(4). The mean rate is much less effective in separating the two groups. The two-sided Wilcoxon rank-sum test indicates that a(4) is higher for preterm neonates than for fullterm neonates at the 5% significance level (P3D0.02). The same test fails to find a significant difference between the mean respiratory rates of preterm and fullterm neonates. RRV is thus lower for more mature neonates, while the mean rate is the same. These results suggest that RRV is a more important indicator of neurological development than the mean respiratory rate.
poster
The timing of oral responses to an artificial nipple (AN) is related to theintrinsic fluctuations in motor activity of newborn rats (Bacher, Robertson& Smotherman, submitted) and late gestation fetal rats (Reilly, Robertson,MacLennan & Smotherman, 1997). Newborn rats' oral responsiveness to an ANis also related to temperature. For example, newborns exhibit more oralgrasp responses when an AN is warm (Koffman, Petrov, Varlinskaya &Smotherman, 1998). Given the importance of temperature in regulatingnewborn rats' motor behavior (e.g., huddle dynamics, Alberts, 1978), weexamined the effects of brief (15 sec) warming on the relationships betweengeneral motor activity and early appetitive behavior.Methods. Newborn rats (N24, 12 females) were studied 3-4 hours afterCesarean delivery. After a 5 min. acclimation, an AN was presented(gentle, perioral stimulation with the tip of the nipple) for 18 min.Experimental subjects received warmth, Control subjects did not. A smalllamp (15 W) was turned on for the first 15 sec of every 2 min period. Thelamp produced a transient increase (3.5 degrees C) in the air temperaturesurrounding the pup which returned to baseline (35 degrees C) after about 1min. The baseline temperature did not increase across the nine 2-minintervals of the experiment (p.78). Motor activity was measured (60 Hz)using a piezoelectric element as a movement sensor. Thresholds were set toremove respiratory signals and noise from the movement data. Oral graspresponses were recorded with an electronic event marker. Each experimentwas videotaped. Data acquisition was controlled by the video signal whichsynchronized the video data and the analog measurements.Variables. Effects of warmth were studied with respect to the number andduration oral grasp responses, level and variability of general motoractivity, and features of cyclic organization in motor activity (frequency,strength and irregularity of the dominant peak, and number of significantpeaks).Results. Experimental (N12) and Control (N12) groups did not differ inthe overall level, variability, and cyclic organization in motor activity.However, on a shorter time scale, pups became more active during warming (p.046). Warmed pups exhibited fewer oral grasp responses than pups notwarmed (M 14 +/- SEM 1.5 vs. 18.7 +/- 1.9, p.059), but longer (21 +/- 5.1vs. 9 +/- 2 sec, p.033).Conclusions and speculations. (1) Brief warmth induced brief motoractivation in newborn rats. However, the absence of effects of briefwarming on the cyclic organization of motor activity suggests that theoscillations are robust. (2) Periodic warmth and/or its accompanying motoractivation facilitated longer grasps in newborn rats. (3) General motoractivity may mediate effects of temperature on oral activity in newbornrats. (4) Warmth and general motor activity may be important features ofthe feeding behavior of newborn human infants. (5) Understanding themechanism(s) of these relationships may provide clues to promoting feedingin human infants.
poster
no abstract
poster
Survival rates for infants born prematurely have improved over the past decade; however, preterm infant care in the perinatal period continues to present a significant health care challenge. A large team of caregivers works towards optimizing outcome for these infants. The developmental specialist is concerned with promoting nursery practices which reduce detrimental stimuli to the lowest possible levels and maximize opportunities for development. Many interventions and environmental modifications have been implemented in nurseries on the premise of providing developmentally appropriate care; however, sufficient objective data regarding the effects of these practices is lacking. One such intervention is the practice of swaddling. Swaddling is defined as the process of tightly wrapping an infant in a blanket, promoting feeling of security, comfort and warmth. The purpose of the present study was to examine effects of swaddling preterm infants. Inclusion criteria for the study were gestational age less than 37 weeks at birth without congenital anomalies. A single subject reversal design (ABA) was used. The independent variable for this study was swaddling the infant, defined as wrapping the baby in a receiving blanket with limbs tightly flexed and hands near mouth. The dependent variables were: number and severity of desaturation events over the study period and hourly samples of behavioral state. On Day 1, baseline recordings of behavioral state and oxygen desaturation events were obtained. On Day 2, recordings were taken during the condition of infant swaddling and on Day 3, baseline recordings were again obtained. Eleven infants have been enrolled in the study to date. Of the infants studied, the majority (n8) had a respiratory condition known as bronchopulmonary dysplasia (BPD), one of the adverse outcomes associated with prolonged dependence on mechanical ventilation. One infant was small for gestational age (SGA) and two infants were premature without complications. Results to date have been analyzed using graphs and plots by individual subjects in accordance with the single subject methodology. Of the infants with BPD, the swaddling appeared to have a positive effect in six of the eight infants studied. The nature of the effect varied. In some of the infants, greater time in behavioral state I (quiet sleep) was observed when swaddled; however, for other infants, more time in behavioral state IV (quiet alert) was noted. Other infants responded positively to swaddling by decreasing time in agitated behavioral states. Likewise, for infants with BPD, the swaddling appeared to be associated with improvement in oxygenation,by decreasing either the number or the severity of desaturation events when swaddled. In the two infants with BPD who did not respond positively to swaddling, there were outlying circumstances. One infant was older at the time the study was initiated (48 weeks) and subsequently died. The other infant had a sepsis workup during the study. The three infants without respiratory disease had no desaturation events during the course of the study. Behavioral state trends in these infants were less dramatic than in the infants with BPD; however, a small tendency to increased proportion of time in the quiet alert behavioral state was noted. These early findings suggest the practice of swaddling infants in the special care nursery may have behavioral and physiologic benefit, particularly for preterm infants with respiratory disease. Further study of infant characteristics associated with response to swaddling and the nature of this response is underway.
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Mothers with normally developing babies were visited in their homes during 13consecutive weeks, when the babies were around 5 to 8 months of age. Basal salivalcortisol measures were taken for both the baby and the mother on arrival. The resultingdata were analyzed with Multilevel Analysis (MlwiN), using a 2-level model.The infants' basal cortisol decreased linearly with age and was negatively related to sleep (i.e.having slept in the half hour preceding the visit). Furthermore, while the infants showedrelative stability across individuals, they displayed great intra-individual variability acrossassessments. Contrarily, the mothers displayed important inter-individual variability,together with a relative stability across assessments. The infants' importantintra-individual variability was not affected by gender, nor time of visit, nor was it relatedto the mothers' basal cortisol. Daily measures of basal cortisol taken in a subgroup ofinfants indicated the day-to-day intra-individual variability to be of the same magnitude as theweek-to-week variability. The question of how the intra-individual variability in basal cortisol affects assessments ofcortisol in infancy is addressed. The aggregation of data with the goal of increasing thereliability of the assessments is shown to be inadequate for infant basal cortisol.