Igino Fagioli

Sleep patterns in infants under continuous feeding from birth.

Continuous parenteral or enteral feeding of infants with major gastrointestinal problems (prolonged diarrhoeas, inflammatory digestive illnesses, anatomical anomalies necessitating surgical intervention, etc.) brings about a prolonged modification in nutritional and environmental conditions. The consequence of eliminating the feeding rhythms of the waking-sleeping rhythm in 16 infants between 1 and 8 months old were studied. In most of the infants the duration of sleep was close to that given by Kleitman in normals. Slightly decreased in 4 of the infants, these durations never showed significant differences from normative values. No delay was observed in the maturation of sleep patterns. The percentage and mean length of periods of quiet sleep were practically identical for all infants but a number of them showed large amounts of ambiguous sleep. The fact that none of these values evolved with age should be stressed. Paradoxical sleep periodicity was similar to that of normal infants, while the quiet sleep-paradoxical sleep cycles were shorter. In conclusion, the absence of feeding rhythms appeared not to modify greatly the sleep maturation and organization.

Sleep states development in the first year of life assessed through 24-h recordings

Sleep measures have been evaluated in 13 normal infants aged between 2 weeks and 11 months 3 weeks, with 24 h polygraphic records. Values over the whole 24 h period show that quiet sleep (QS) increases with age while paradoxical sleep (PS) and ambiguous sleep (AmbS) decrease; however, when the 24 h period is split into two periods (day-time, night-time) it can be seen that QS increases only during the night-time while PS and AmbS decrease only during the day-time. The QS in older subjects becomes mainly located at the beginning of the night-time period, when particularly long phases take place. The distribution during the night-time of PS (in terms of the amount and of the mean duration of the phases) does not change with age.

Sleep organization in the first year of life: Developmental trends in the quiet sleep–paradoxical sleep cycle

The night sleep of 48 healthy drug‐free infants, aged 1–54 weeks, was recorded and analysed in order to show how cycles contribute to sleep episode organization and how the balance among different sleep states (i.e. quiet sleep, paradoxical sleep and ambiguous sleep) within cycles changes as a function of age.

Time course of night sleep EEG in the first year of life: a description based on automatic analysis

The aim of this study is to describe the time course of night sleep in the first year of life. Forty-eight infants aged between 1 and 54 weeks were polygraphically recorded for 1 night. The central occipital EEG derivation was processed with a lab computer in order to obtain every 30 sec an EEG parameter value. The parameter is based on the joint frequency-amplitude distribution of the EEG and displays fluctuations between 2 extreme levels, high voltage low frequency (HVLF) and low voltage high frequency (LVHF). The range of the fluctuations between HVLF and LVHF increases from the period of 1-6 weeks to the period of 7-14 weeks. A further increase of the parameter range occurs after 24 weeks, which remains restricted to the first half of the night. The recurrence time of LVHF and HVLF episodes (possibly corresponding to quiet sleep paradoxical sleep cycles) is about 56 min and does not change with age in the first year of life.

REM latency: Development in the first year of life

The development of REM latency in the first year of life was investigated in two groups of 10 infants each. While 10 infants were normal, the other 10 underwent continuous feeding for various gastrointestinal diseases. Each infant was continuously recorded polygraphically for 24 h. While younger infants (less than or equal to 3 months) manifested predominantly shorter REM latencies (less than or equal to 8 min), older infants (4-13 months) produced a mixed distribution of short and long REM latencies. The total distribution of the REM latencies appears to be bimodal with latencies either shorter than 8 min or longer than 16 min. It is only in the group of older infants that the temporal distribution of REM latencies constitutes a diurnal rhythm, with the longest latencies in the interval between 12:00 and 16:00 and the shortest between 4:00 and 8:00. In the group of older infants, REM latency also depends on the duration of prior wakefulness. Long REM latencies are significantly more often preceded by long episodes of wakefulness than are short REM latencies. The different feeding conditions had only a minor effect on REM latency.

Spontaneous awakenings from sleep in the first year of life.

Spontaneous awakenings from nocturnal sleep were studied in a sample of 48 healthy infants (M = 26, F = 22), in four age groups (1 to 7 weeks, 8 to 15 weeks, 17 to 22 weeks, 25 to 54 weeks). Consistent with previous data, the number of awakenings is reported less frequently at later ages, owing to a lower frequency of awakenings out of REM sleep. Like young adults, infants in all age groups awake more often from REM than from quiet sleep (QS); this is particularly evident in the first 6 months of life, less so in the second. The duration of the bouts of wakefulness following awakenings remains stable with age. Awakenings out of QS are followed by longer periods of wakefulness than those out of REM sleep, although in older infants the duration is considerably reduced. Night sleep first shows a decrease in the number of awakenings out of REM sleep and then continues after the sixth month of life with the shortening of the wakefulness after awakenings out of QS. In the two younger groups, the distribution of the awakenings shows two main peaks and one main peak differently located during the night; a polymodal pattern appears in group 3, and is even more evident in group 4. It should be stressed that several changes as a function of age occur in the second 6 months of life, indicating this as a period of intense developmental change in sleep-wake rhythms.

Sleep for development or development for waking ? some speculations from a human perspective

The issue of the relationship between sleep and development could be posed in the following terms: (1) does sleep have a function for development? and (2) which is the specificity of sleep function during development? Is it possible to assess critical ages of emergence and decline of specific sleep functions? The results of recent investigations related to the so-called ontogenetic hypothesis for the function of rapid eye movement (REM) sleep will be reviewed; suggestions are put forward concerning the possible role of non-rapid eye movement (NREM) sleep. Because of the difficulties to provoke long-lasting sleep deprivation in humans during development, two different approaches were used. The results of one set of analyses concerned the secretion of growth hormone during sleep under normal and pathological conditions and the relationship between sleep organization and nutritional supply utilisation in infants and children. The second approach aimed at investigating the long-term development of children suffering from sleep abnormalities at earlier ages. Furthermore, the role of dreaming during development will be discussed. The data summarized here only partly support the function of sleep during development; we would like to underscore the difficulty to dissociate the function of sleep from that of waking.

Spontaneous awakening from sleep in infants

Spontaneous awakenings from sleep were studied in a group of 20 infants whose sleep-waking patterns were recorded polygraphically for 24 h. While 10 infants were orally fed the other 10 underwent continuous feeding for various gastrointestinal diseases. Spontaneous awakening from sleep was analysed with regard to the prior sleep state, age and feeding condition. Infants awoke preferentially out of REM sleep and less often out of non-REM sleep. The feeding condition had no significant influence on the distribution of awakenings. The propensity for REM awakenings was significantly greater than would have been expected according to the REM sleep amount. This tendency was more pronounced for younger (less than or equal to 3 months) than for older (greater than or equal to 4 months) infants. REM sleep episodes which were interrupted by awakenings were significantly shorter than uninterrupted ones, since awakenings occurred predominantly shortly after REM sleep onset. It is proposed that the specific pattern of brain activity during REM sleep facilitates the transition from sleep into the waking state, particularly in the youngest infants.

Effect of early human malnutrition on waking and sleep organization

In order to evaluate the effect of early human malnutrition (EHM) on waking and sleep organization, a group of 12 infants malnourished (M) from birth were investigated in their first year of life through 24-h polygraphic recordings. The same infants were recorded again after nutritional rehabilitation (R). A group of 12 age-paired normal infants served as controls (C). Both young (less than 4 months) and older (greater than or equal to 4 months) M infants showed a distribution of classes of waking duration different from that of C while the trend with age of the longest sustained waking (LSW) is similar in M and in C infants. The durations distribution of sleep episodes does not differ between M and C infants, while the longest sustained sleep (LSS) is significantly shorter in M than in C infants. The LSW is less clearly located in the day-time and the LSS is less clearly located in the night-time in M infants as compared to C infants. The quiet sleep-paradoxical sleep cycles are significantly shorter in older M infants because of the reduction of quiet sleep. Nutritional rehabilitation tends to improve waking and sleep organization.

Dynamics of EEG background activity level within quiet sleep in successive cycles in infants

We investigated in infants the emergence of the trends of the EEG synchronization throughout quiet sleep (QS) as a function of the QS rank. The night sleep of 3 groups with 6 subjects each (aged respectively 9-18 weeks, 21-47 weeks, and 16-45 years) was recorded. A parameter value reflecting the degree of synchronization of the EEG background activity for successive epochs was computed by automatic analysis. For each QS phase 3 indicators of the dynamics of the time course of the EEG parameter activity were determined: the range (difference between the EEG parameter value at the beginning of the QS episode and that at the trough), the trough latency (after QS onset), and the rate of synchronization (range/trough latency). The range and the trough latency increased with age, whereas the rate of synchronization decreased. The range and the rate of synchronization decreased in the successive cycles, whereas the trough latency increased. These results provide further support for the hypothesis of the early emergence of the process S mechanisms and suggest that the framework of the 2-process model could account also for the development of both the EEG background activity dynamics and the sleep-wake organization.