Sleep architecture is related to the season of PSG recording in 8-month-old infants

The role of light exposure in infant circadian rhythm establishment: A scoping review perspective

Environmental light exposure plays a role in the entrainment of the infant circadian rhythm, which is crucial for growth and development. This scoping review aims to evaluate existing literature linking the role of light exposure in the development of the infant circadian rhythm. This scoping review is conducted in accordance with the PRISMA-ScR guidelines. The search strategy was conducted in a total of six databases (PubMed, Cochrane Database of Systematic Reviews, Science Direct, Google Scholar, Taylor and Francis, and Wiley) as of August 2024. Reviews, narrative studies, observational studies, and experimental studies published from 2012 to 2024 were extracted. These studies discussed the role of light exposure on the development of infant circadian rhythm. A total of 25 studies were retrieved (3 observational studies, 6 experimental studies, and 16 reviews). Evidence showed that cycled lighting is beneficial for the entrainment of the infant circadian rhythm according to the 24-h light-dark cycle. Cycled lighting improved nighttime sleep and daytime wakefulness, promoting optimum growth and development. Limited experimental studies were conducted due to the ethical considerations of infants as study participants. Conclusions: Given the benefits of cycled lighting in the development of the circadian rhythm development, it should be implemented in both healthcare and home settings to promote optimum growth and development of the infant.

Postnatal Development of the Circadian Rhythmicity of Human Pineal Melatonin Synthesis and Secretion (Systematic Review)

Introduction: According to current knowledge, at birth, the pineal gland and melatonin receptors are already present and the suprachiasmatic nucleus is largely functional, and noradrenaline, the key pineal transmitter, can be detected in the early foetal period. It is still unclear why the pineal gland is not able to start its own pulsatile synthesis and secretion of melatonin in the first months of life, and as a result, infants during this time are dependent on an external supply of melatonin. Method: The causes and consequences of this physiological melatonin deficiency in human infancy are examined in a systematic review of the literature, in which 40 of 115 initially selected publications were evaluated in detail. The references of these studies were checked for relevant studies on this topic. References from previous reviews by the author were taken into account. Results: The development and differentiation of the pineal gland, the pinealocytes, as the site of melatonin synthesis, and the development and synaptic coupling of the associated predominantly noradrenergic neural pathways and vessels and the associated Lhx4 homebox only occurs during the first year of life. Discussion: The resulting physiological melatonin deficiency is associated with sleep disorders, infant colic, and increased crying in babies. Intervention studies indicate that this deficiency should be compensated for through breastfeeding, the administration of nonpooled donor milk, or through industrially produced chrononutrition made from nonpooled cow's milk with melatonin-poor day milk and melatonin-rich night milk.

Contributions of the light environment and co-sleeping to sleep consolidation into nighttime in early infants: A pilot study

BACKGROUND

Sleep consolidation into nighttime is considered the primary goal of sleep development in early infants. However, factors contributing to sleep consolidation into nighttime remain unclear.

AIM

To clarify the influences of the light environment and nighttime co-sleeping on sleep consolidation into nighttime in early infants.

STUDY DESIGN

Cross-sectional study.

SUBJECTS AND METHODS

Sleep-wake time and light stimulation were measured in infants for 4 consecutive days using actigraphy. The infants' mothers were asked to complete a sleep events diary and a questionnaire about childcare, including "co-sleeping", defined as when the infant and mother slept on the same surface throughout the night.

OUTCOME MEASURES

The data were analyzed with a focus on daytime and nighttime sleep parameters.

RESULTS

Daytime light stimulation reduced daytime "active sleep", tended to reduce daytime sleep, and increased daytime waking. Nighttime light stimulation reduced nighttime "quiet sleep" and nighttime sleep and increased nighttime waking. Co-sleeping reduced nighttime waking, and, as a result, nighttime sleep time and sleep efficiency increased. Co-sleeping reduced daytime sleep and tended to increase daytime waking. Consequently, co-sleeping tended to increase the ratio of nighttime sleep to daytime sleep.

CONCLUSIONS

The present findings suggest that an appropriate light environment promotes daytime waking and nighttime sleep in early infants, but it does not contribute to sleep consolidation into nighttime by itself. On the other hand, co-sleeping may promote sleep consolidation into nighttime. Therefore, further methods for safe co-sleeping need to be established while avoiding risk factors for sudden unexpected death in infancy/sudden infant death syndrome.

Seasonal variations of nonmotor symptoms in patients with Parkinson's disease in Southeast China

BACKGROUND

Studies suggest seasonal fluctuations of symptoms in Parkinson's disease (PD) patients in Western countries. However, the association between seasonal change and variation in nonmotor symptoms (NMS) in Chinese PD patients is unclear. Here, we studied whether there is a change rule with annual cycle with severity of NMS for patients with PD in Southeast China.

METHODS

We studied 1005 PD patients between April 2008 and October 2020. Patients were classified into four seasons according to the 24 Chinese solar terms, based on assessment date. We compared comprehensive NMS scales and polysomnography parameters among groups and conducted further analysis of disease severity.

RESULTS

Among the 1005 patients studied, the mean age was 64.2 ± 9.7 years and 569 (56.6%) of them were men. Relative to the summer group, patients assessed during winter had higher Scales for Outcomes in Parkinson's disease-Autonomic Dysfunction (SCOPA-AUT) scores ( P  = 0.045). The sleep efficiency factor scores of Pittsburgh Sleep Quality Index in patients were higher during spring than summer ( P  = 0.009). Among patients who completed polysomnography during the same period ( n  = 135), compared with summer follow-ups, we observed a higher percentage of NREMS1 in winter and spring follow-ups ( P  = 0.042, P  = 0.011), a higher NREMS1 time in spring follow-ups ( P  = 0.0024), a lower NREMS2 time in winter follow-ups ( P  = 0.007), and a higher percentage of phasic rapid eye movement (REM)-sleep without atonia in autumn and winter follow-ups ( P  = 0.026 and P  = 0.020, respectively). In a subset of patients with PD and REM sleep behavior disorder (RBD; n  = 182), those visited during winter had higher scores for RBD questionnaire-Hong Kong and its factor 1 (dream-related sub-score) than those visited during summer ( P  = 0.034, P  = 0.020). We observed similar findings for SCOPA-AUT and sleep efficiency factor scores in early stage patients in subgroup analysis.

CONCLUSIONS

PD patients assessed for follow-up during summer showed less severe symptoms of autonomic dysfunction and RBD symptoms than those assessed in winter, and less sleep disturbance than those in spring and winter, suggesting that seasonal change and NMS fluctuation are related, especially in patients with early stage PD.

The Architecture of Early Childhood Sleep Over the First Two Years

INTRODUCTION

The architecture and function of sleep during infancy and early childhood has not been fully described in the scientific literature. The impact of early sleep disruption on cognitive and physical development is also under-studied. The aim of this review was to investigate early childhood sleep development over the first two years and its association with neurodevelopment.

METHODS

This review was conducted according to the 2009 PRISMA guidelines. Four databases (OVID Medline, Pubmed, CINAHL, and Web of Science) were searched according to predefined search terms.

RESULTS

Ninety-three studies with approximately 90,000 subjects from demographically diverse backgrounds were included in this review. Sleep is the predominant state at birth. There is an increase in NREM and a decrease in REM sleep during the first two years. Changes in sleep architecture occur in tandem with development. There are more studies exploring sleep and early infancy compared to mid and late infancy and early childhood.

DISCUSSION

Sleep is critical for memory, learning, and socio-emotional development. Future longitudinal studies in infants and young children should focus on sleep architecture at each month of life to establish the emergence of key characteristics, especially from 7-24 months of age, during periods of rapid neurodevelopmental progress.

Season is related to the slow wave and sigma activity of infants and toddlers

OBJECTIVE/BACKGROUND

Slow wave activity (SWA) and sigma frequency activity (SFA) are hallmarks of NREM sleep EEG and important indicators of neural plasticity, development of the central nervous system, and cognition. However, little is known about the factors that modulate these sleep EEG activities, especially in small children.

PATIENTS/METHODS

We analyzed the power spectral densities of SWA (1-4 Hz) and SFA range (10-15 Hz) from six EEG derivations of 56 infants (8 months) and 60 toddlers (24 months) during their all-night sleep and during the first and the last half of night sleep. The spectral values were compared between the four seasons.

RESULTS

In the spring group of infants, compared with the darker seasons, SFA was lower in the centro-occipital EEG derivations during both halves of the night. The SWA findings of the infants were restricted to the last half of the night (SWA2) and frontally, where SWA2 was higher during winter than spring. The toddlers presented less frontal SWA2 during winter compared with autumn. Both age groups showed a reduction in both SWA and SFA towards the last half of the night.

CONCLUSIONS

The sleep EEG spectral power densities are more often associated with seasons in infants' SFA range. The results might stem from seasonally changing light exposure, but the exact mechanism warrants further study. Moreover, contrary to the adult-like increment of SFA, the SFA at both ages was lower at the last part of the night sleep. This suggests different regulation of spindle activity in infants and toddlers.