OBJECTIVETo investigate the development of nocturnal sleep pattern in infants.

METHODSFifty healthy full-term newborns born in Chongqing Maternal and Child Health Care Hospital were chosen for a prospective longitudinal study. A non-invasive sleep monitor, Actiwatch, was used to monitor infants' 12 sleep parameters on the 10th day, 28th day, the first Tuesday at the 2nd, 3rd, 4th, 5th, 6th, 9th and 12th month after birth, each monitoring time lasting 60 hours. All sleep parameters were analyzed by two-level mixed effect model.

RESULTSTwenty-two boys and 25 girls completed the whole follow-up study. From birth to the 12th month after birth, the nocturnal sleep onset latency (NSOL) decreased by about 48% at 3 months of age and by 83% at 6 months of age. The nocturnal sleep efficiency (NSE%) increased from 66% to 87%, the nocturnal total sleep time (NTST) increased from 416 minutes to 517 minutes, and the longest nocturnal continuous sleeping time (L-NCST) increased from 197 minutes to 327 minutes. NSE%, NTST and L-NCST increased with age (P<0.01). The 3rd to 12th month ratios of NSE%, NTST and L-NCST were 86%, 84% and 72%, respectively, and the 6th to 12th month ratios of those were 97%, 91% and 94%, respectively. The nocturnal total wake time (NTWT) and longest nocturnal continuous waking times (L-NCWT) decreased with age (P<0.01). The decline speeds in the first half year were 5-6 times of those in the second half year after birth (P<0.05). NTST, nocturnal continuous sleeping ability and NSE% in boys were lower than those in girls (P<0.05).

CONCLUSIONSInfantile nocturnal sleep patterns develop rapidly during the first 6 months, especially within the first 3 months after birth. Partial infantile sleep parameters are related to gender.