Reliable individual differences in preterm infants' excitation management.

2 large independent cohorts of preterm infants ranging between 32 weeks and term were given a neurobehavioral assessment (the NAPI) that measures, among other things, individual differences in excitation management. This assessment, which has high test-retest reliability and developmental and clinical validity, presents each infant with an identical sequence of events. Infant reactions to the standard stimulation provided by this assessment were used as measures of differential excitability. The results showed that over a period of weeks, preterms were highly self-consistent in their reactions. Highly reliable individual differences between infants were also seen. The self-consistencies and individual differences were independent of the infants' prior medical complications. With very few exceptions, these results replicated over the 2 independent cohorts. The individual consistencies and differences in excitation management found in this study might predispose children to later differences in temperament.

Prediction of the development of low birth weight preterm infants by a new neonatal medical index.

A new neonatal medical index (NMI) was used to predict the mental and motor development of low birth weight, preterm infants up to 3-years-old. The NMI is a summary score of only a few clinically salient items that are readily available on brief chart review. The sample consisted of 512 of 608 infants randomly assigned to the control group of the eight-site Infant Health and Development Program and on whom the complete set of developmental outcome measures was available. The developmental tests administered were the Bayley Scales at 12 and 24 months and the Stanford-Binet at 3 years. The findings indicated the NMI was predictive of later cognitive and motor development, and in infants born weighing less than 1500 g, the effects of neonatal medical complications continued to adversely influence these children's development to at least 3 years of age. In the heavier babies the developmental effects of sociodemographic factors predominated by 24 months and beyond.

Establishing the reliability and developmental validity of a neurobehavioral assessment for preterm infants: a methodological process.

The Neurobehavioral Assessment of the Preterm Infant was developed in 3 phases: a pilot study, an exploratory study, and a validation study. In the exploratory study, clusters characterized by conceptual cohesion and face validity were systematically subjected to statistical analyses to determine whether they also had high test-retest reliability and developmental validity. In the validation study, a shortened version of the test was used with an independent cohort of 290 preterm infants. A step-by-step methodological process was used to test whether the results from the exploratory study would generalize over cohorts, different versions of the test, different hospitals, and changes in examiners. This process yielded 7 highly stable, developmentally valid, and representative preterm neurobehavioral functions that generalized over the exploratory and the validation studies. These were: motor development and vigor, scarf sign, popliteal angle, alertness and orientation, percent asleep ratings, irritability, and vigor of crying.

Sleep enhanced and irritability reduced in preterm infants: differential efficacy of three types of waterbeds.

The purpose of this study was to determine whether waterbeds enhance preterm infants' sleep and reduce irritability, and whether plain, continuously, or intermittently oscillating waterbeds are differentially effective in producing these effects. The baseline states and motility of 52 stable preterm infants were assessed on two consecutive days for 100 minutes each. The infants then were randomly assigned to four groups: a control group who remained on the incubator mattress, or to one of the three experimental groups, each using a different waterbed. On days 3 and 4 in the assigned test condition, the infants' states and motility were again assessed for 100 minutes each day. The results indicate that, compared with infants in the control group, infants assigned to any of the waterbed groups slept significantly more and better, had significantly fewer unsmooth movements, state changes, and transitional states, and were significantly less irritable. Differential treatment effects were found, with infants on continuously oscillating waterbeds showing the most marked reductions in irritability, restlessness, state changes, and unsmooth movements. Thus, to enhance restful sleep and to reduce irritability and/or restlessness, it would be clinically advantageous to use waterbeds in the care of preterm infants. Since even the simple, nonoscillating waterbed improved sleep and reduced restlessness, the use of these beds would be the least costly to achieve these effects.

Infant stimulation. Issues of theory and research.

This article addresses the topic of infant stimulation from two directions. The first is the developmental relevance of stimulation for infants in general; the second is the issue of differences in responsiveness to stimulation on the part of individual infants. The author will elucidate the conceptual differences between these two issues by giving examples, mostly from intervention studies with preterm infants.

Stable individual differences in developmentally changing preterm infants: a replicated study.

In a longitudinal study with the Neurobehavioral Maturity Assessment (NB-MAP), developmental changes and stability of individual differences were assessed in 2 independent samples of preterm infants ranging from 32 weeks conceptional age to term. Individual stability of response was assessed using regression analysis with repeated measures on subjects. The large majority of the functions tested showed highly significant developmental gains with age and highly significant individual stability of performance across age. These findings replicated well across the 2 cohorts. The results are discussed in the light of the neurobiological stage of development of preterm infants during the last 8 weeks prior to term.

A methodological approach to developing an assessment procedure for testing the neurobehavioral maturity of preterm infants.

Using data from 179 preterm infants, a neurobehavioral maturity assessment was developed by using a process in which clusters characterized by conceptual coherence and face validity were systematically subjected to statistical analyses designed to test whether they also had high test-retest reliability, statistical cohesion, and developmental validity. The psychometric soundness of the test items was made a precondition for their inclusion into the assessment procedure. Also tested were cluster redundancy, as well as the impact of gestational and conceptional age, and of postbirth influences on the functions tested. 8 dimensions of neurobehavioral functioning were found to be stable with a test-retest reliability of at least .6 or higher on 2 consecutive days, nonredundant and developmentally valid. They were: Active Tone/Motor Vigor, Alertness and Orientation, Excitation Proneness, Inhibition Proneness, Scarf Sign, Popliteal Angle, Maturity of Vestibular Response, and Vigor of Crying.

Does a vigorous feeding style influence early development of adiposity?

A prospective study of a cohort of healthy infants observed from birth to 2 years of age was carried out to investigate factors influencing the development of early adiposity. Infant suckling was measured in the laboratory twice during the first month of life. Multiple regression analyses revealed that parental educational level and a measure of feeding behavior, the interval between bursts of suckling, accounted for 18% of the variance in triceps skinfold measures at 1 year of age. A lower level of education and shorter interburst interval were associated with increased adiposity. Two feeding variables, pressure of suckling and the number of reported feeds per day, accounted for 21% of the variance in skinfold thickness at 2 years of age. Fewer, but larger, feeds and a higher sucking pressure were associated with a greater degree of adiposity. It seems that a vigorous infant feeding style, consisting of sucking more rapidly, at higher pressure, with a longer suck and burst duration, and a shorter interval between bursts of sucking, is associated with higher caloric intake and greater adiposity. The early development of this feeding style suggests that it may be a genetically endowed behavior. Breast-feeding protected against early adiposity only to the age of 6 months in this cohort of infants.

Activity level and behavioral style in young children.

A portable microcomputer activity recorder was used to measure a 24-hour sample of activity level in 4-to 8-year-old children. Recorded activity level was not related to parental perception of activity level and did not differentiate children with differing behavioral styles. Parental perception of activity level, on the other hand, significantly differentiated children's behavioral style. Parents may be responding to a composite image of the child's behavioral style when they rate activity level. We urge caution in the use of the term 'activity level', which may have different meanings according to how it is measured.

Physical activity and adiposity: a longitudinal study from birth to childhood.

Physical activity was reassessed in cohort of 52 children aged 4 to 8 years whose activity had been measured during the first 3 days of life. Neonatal adiposity was not significantly correlated with parental adiposity, neonatal physical activity, or gender, nor was neonatal activity significantly correlated with adiposity in childhood. Neonatal adiposity did not predict adiposity in childhood. However, in a stepwise multiple regression, parental adiposity and the children's daytime high activity levels were significantly associated with childhood adiposity. The age or gender of the child did not significantly correlate with childhood adiposity. As parental adiposity increased or daytime high activity of a child decreased, the adiposity in a 4- to 8-year-old child was likely to increase.

The relation between neonatal and later activity and temperament.

Evidence from several longitudinal studies suggests that individual activity characteristics tend to persist over time and to influence the development of temperamental style. The activity of 50 children whose motility had been monitored by an electronic activity monitor when they were neonates was again monitored by an ambulatory microcomputer when they were 4-8 years old. Additionally, the parents of these children filled out the Behavioral Style Questionnaire by McDevitt and Carey. The results showed that the level of the children's day and night activity was unrelated. The vigor of neonatal movements was later positively related to high daytime activity. Also, the least vigorous infants tended to become the most inactive children during the day. The results further showed that the most active neonates became children who, as perceived by their parents, tended to approach rather than withdraw from new experiences.

Effects of vestibular-proprioceptive stimulation on the neurobehavioral development of preterm infants: a pilot study.

This paper reports the results of an intervention study which assessed the effects of compensatory vestibular-proprioceptive stimulation provided by waterbed flotation on the neurobehavioral development of preterm infants. The subjects, who were randomly assigned to experimental and control groups before they were four days old, consisted of infants who were on ventilators for severe RDS. Twenty infants were tested with a new neurobehavioral assessment procedure when they were between 34 and 35 weeks conceptional age. The examiner, a pediatric neurologist, was unaware of the group status of the subjects he examined. The results showed that infants in the experimental group performed significantly better in attending and pursuing animate and inanimate visual and auditory stimuli, demonstrated more mature spontaneous motor behavior, showed significantly fewer signs of irritability and/or hypertonicity and were more than twice as often in th visually alert, inactive state. The assessment procedure, which can be used for longitudinal evaluation of infants ranging between 24 and 36 weeks conceptional age, shows promise of becoming generally useful as a research instrument. Our preliminary results show that the procedure discriminated between an experimental and control group, that inter-observer reliability was readily established and that test-retest reliability is very high in a number of important areas of neurobehavioral functioning.

Effects of water beds on the sleep and motility of theophylline-treated preterm infants.

With evidence accumulating that the sleep of infants receiving theophylline is sharply reduced, this study tested whether water bed flotation could increase the sleep and attenuate the restlessness of preterm infants treated with theophylline for apnea. Seventeen preterm infants served as their own control, off and on gently oscillating water beds. The infants' sleep and motility were assessed on days 3 and 4 during the experimental and control conditions. While on the water bed, the infants had significantly more quiet and active sleep, shorter sleep latencies, fewer state changes, less restlessness during sleep, less waking activity, and fewer jittery and unsmooth movements. Reductions in wakefulness and state changes on the water bed were significantly greater, the longer the infants were receiving theophylline, but they were unrelated to theophylline levels which, for the group as a whole, were relatively low. Residual apnea was not reduced on the water bed. Although water bed flotation significantly improved the infants' sleep and motility, stable behaviour differences among the infants were observed across the experimental and control conditions.

Stability of individual differences of neonatal motor and crying patterns.

Longitudinal research suggests that characteristic levels of individual energy expenditure are enduring over time and influencing personality development. To measure characteristic levels of energy output at the very beginning of life, the activity and crying patterns of 72 normal neonates were monitored for 1-3 days by an electronic activity monitor. This monitor measures crying, noncrying, and total activity of various amplitudes and cry time. Day-to-day stability was highly significant in daytime crying, noncrying and crying activity, and median amplitude of noncrying movements. The amplitude of noncrying movements had the highest day-to-day stability, with correlations of .69-.80 This measure of the vigor of the infants' movements was not related to the infants' activity level as expressed in the frequency of movements and was not confounded by the infants' crying. The activity and crying measures were not significantly affected by the infants' sex or weight, length of labor, maternal parity, or by the analgesic drugs used during labor and delivery. Over the first 3 days of life, the amplitude or vigor of the infants' movements increased, while the frequency of motions did not change significantly.

Relation between prenatal maternal blood pressure and infant irritability.

Chisholm et al. [4], using samples of Navajo and Malaysian newborns, found a significant positive relation between maternal normotensive blood pressures during the second trimester of pregnancy and at delivery and infant irritability in response to the Brazelton Examination. Measuring spontaneous crying with an electronic activity monitor and using a white middle-class American population, this relation was replicated for mothers with normotensive blood pressures during the third trimester of pregnancy. The combined findings of the 3 studies seem to suggest that maternal blood pressure in the latter part of pregnancy, even when within normal limits, is a factor in how irritable normal newborn infants are.

Reduction of sleep apnea and bradycardia in preterm infants on oscillating water beds: a controlled polygraphic study.

The sleep and respiratory patterns of eight apneic preterm infants were polygraphically recorded for 24 hours. This polygraphic study was designed to test and extend our previous finding that gently oscillating water beds reduce apnea in premature infants. The infants who ranged in gestational age from 27 to 32 weeks and in birth weight from 1,077 to 1,650 gm served as their own controls, off and on the water bed. The 24-hour recordings were divided into four time blocks with the infant being placed on the water bed during alternate six-hour periods. Apnea was significantly reduced while the infants were on the oscillating water beds, with the longest apneic periods and those associated with severe bradycardia being reduced the most. Reduction of apnea was most consistent during indeterminate sleep and most pronounced during quiet sleep. Short respiratory pauses and periodic breathing were not significantly reduced. Reductions of central, obstructive, and mixed apneas were approximately equal.