Synchronizing circadian rhythms in early infancy

Relationship between circadian salivary melatonin levels and sleep-wake behavior in infants

BACKGROUND

There have been calls for more aggressive intervention for infants with failure in development of a sleep-wake rhythm. If development of the 'biological clock' in infants can be assessed by measuring melatonin, this may provide a useful indicator of the sleep-wake rhythm development. Thus, we investigated relationship between circadian salivary melatonin concentrations and sleep-wake behavioral parameters in infants.

METHODS

Sixty-seven mothers who had infants aged 3-15 months were requested to record sleep-wake behavior of their baby for 2 days, and to collect their baby's saliva four times daily in the morning (06:00-09:00 h), noon (11:00-13:00 h), evening (16:00-18:00 h), and night (19:00-22:00 h) for measurement of melatonin concentrations by ELISA.

RESULTS

The mean melatonin concentrations of the saliva were: morning 40 ± 4 pg/mL, noon 14 ± 3 pg/mL, evening 15 ± 3 pg/mL, and night 23 ± 4 pg/mL. The melatonin concentrations, at each measurement point, were highest in infants aged 3-5 months, and decreased as age increased. Morning melatonin concentrations showed a negative correlation with nocturnal sleep duration (P<0.05). Increased morning concentrations were related to early waking time (P<0.05). In infants with open air baths on most days, evening and night melatonin concentrations were significantly lower (P<0.05).

CONCLUSION

Salivary melatonin concentrations in infants between 06:00 and 22:00 decreased by age, and elevation of morning values may indicate an immature sleep-wake rhythm. Frequent open air baths may contribute to decreased melatonin levels.

Perinatal nutrient restriction induces long-lasting alterations in the circadian expression pattern of genes regulating food intake and energy metabolism

OBJECTIVE

Several lines of evidence indicate that nutrient restriction during perinatal development sensitizes the offspring to the development of obesity, insulin resistance and cardiovascular disease in adulthood via the programming of hyperphagia and reduced energy expenditure. Given the link between the circadian clock and energy metabolism, and the resetting action of food on the circadian clock, in this study, we have investigated whether perinatal undernutrition affects the circadian expression rhythms of genes regulating food intake in the hypothalamus and energy metabolism in the liver.

DESIGN

Pregnant Sprague-Dawley rats were fed ad libitum either a control (20% protein) or a low-protein (8% protein) diet throughout pregnancy and lactation. At weaning, pups received a standard diet and at 17 and 35 days of age, their daily patterns of gene expression were analyzed by real-time quantitative PCR experiments.

RESULTS

17-day-old pups exposed to perinatal undernutrition exhibited significant alterations in the circadian expression profile of the transcripts encoding diverse genes regulating food intake, the metabolic enzymes fatty acid synthase and glucokinase as well as the clock genes BMAL1 and Period1. These effects persisted after weaning, were associated with hyperphagia and mirrored the results of the behavioral analysis of feeding. Thus, perinatally undernourished rats exhibited an increased hypothalamic expression of the orexigenic peptides agouti-related protein and neuropeptide Y. Conversely, the mRNA levels of the anorexigenic peptides pro-opiomelanocortin and cocaine and amphetamine-related transcripts were decreased.

CONCLUSION

These observations indicate that the circadian clock undergoes nutritional programming. The programming of the circadian clock may contribute to the alterations in feeding and energy metabolism associated with malnutrition in early life, which might promote the development of metabolic disorders in adulthood.

Development of fetal and neonatal sleep and circadian rhythms

The origin of sleep and circadian rhythms development is found during the fetal period. Both quiet (NREM) and active (REM) sleep are distinguishable during the last 10 weeks of gestation. Comparable to fetuses, low risk preterm infants recorded at 30-40 weeks postconceptional age, had a similar development of sleep i.e. an increase in quiet sleep and a decrease in indeterminate sleep. A further development in sleep organization characterized by increased slow wave and spindle activity during quiet sleep and coupling with circadian rhythm takes place during the first 6 months of life in both term and preterm infants.Circadian rhythm of fetal heart rate synchronized with maternal rest-activity, heart rate, cortisol, melatonin, and body temperature rhythms is present during the last 10 weeks of gestation. Although maternally influenced, circadian rhythm antenatally becomes ultradian at birth. Both preterm and term infants show a significant increase in circadian body temperature rhythm amplitude during the first 3 months of life.

Preterm infant temperature circadian rhythm: possible effect of parental cosleeping

The purpose of this study was to describe the circadian rhythm of abdominal skin temperature and explore factors related to the timing of circadian rhythm acrophase. Thirty-four preterm infants (gestational age 26 to 33 weeks) were studied in the home environment at 44 to 46 weeks postconceptional age. Insulated abdominal skin was monitored continuously, and parents recorded sleep/wake activity over a 24-h period. Circadian rhythm was analyzed using cosinor analysis. Using MANCOVA, the effects of cosleeping, feeding method, night feeding, hospital stay, time home, and illness on acrophase were determined. Infants demonstrated evidence of developing circadian rhythm of temperature. Cosleeping and length of hospital stay were significantly related to acrophase. The mean acrophase for cosleeping infants was 07:44 (95% confidence interval = 05:12, 11:08), whereas that for non-cosleeping infants was 22.05 (95% confidence interval = 17:31, 01:42). Proximity with parents during nighttime hours may serve to entrain preterm infant circadian rhythm.

Influence of light in the NICU on the development of circadian rhythms in preterm infants

The fetal biological clock is an endogenous clock capable of generating circadian rhythms and responding to maternal entraining signals. By at least the third trimester of pregnancy fetal diurnal rhythms are entrainable by maternal day-night rhythms. Maternal illness during pregnancy and premature birth are obvious clinical factors that may adversely affect circadian rhythm development. Premature birth of the fetus has a most dramatic impact on maternal fetal interactions. The effect on biorhythms appears to be temporary and is greatest on the most immature infants. The results to date support the importance of fetal circadian rhythms and the relative lack of these rhythms in the preterm infant. It is well known that growth and development in the prematurely born infant are influenced by a multitude of factors; clearly, the neonatal intensive care unit is not a surrogate for the maternal placental unit. This article reviews what is known about circadian development in the human infant with an emphasis on the unique circumstances of the preterm infant. The research on the short- and long-term effects of environmental interventions on circadian, sleep, and neurologic development is discussed. Although an earlier onset of circadian development did not result with cycled lighting in the neonatal nursery, there may still be important biological effects that have not been studied. There are sufficient data to state that there is no reason for continuing a chaotic, noncircadian environmental approach for the care of the prematurely born infant.

Movements in autistic disorder

Autistic disorder, an extremely disabling syndrome with onset in early childhood, is associated with multiple comorbid conditions. Although autistic disorder is heterogeneous in its manifestations, there is a subgroup of individuals with autistic disorder who display movements that appear to be unique for the disorders. Hand flapping and a variety of movements termed stereotypies may be pathognomonic of autistic disorder. Therefore, identification of a movement disorder characteristic of autistic disorder may imply that the individual has autistic disorder.