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).


CONCLUSIONS
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.
Shinohara
Hitomi
H
Department of Maternity Child Nursing, Akita University Graduate School of Health Science, Akita, Japan.
Kodama
Hideya
H
D000367:Age Factors; D015415:Biomarkers / Q000378:metabolism; D057906:Circadian Clocks / Q000502:physiology*; D004777:Environment; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D012463:Saliva / Q000378:metabolism*; D012890:Sleep / Q000502:physiology*; D020178:Sleep Disorders, Circadian Rhythm / Q000378:metabolism*
D015415:Biomarkers; D008550:Melatonin