Sleep architecture is related to birth season in 1-month-old infants

ABSTRACT

Individual variation in sleep quality, quantity, and architecture is pronounced in small infants. Reasons for this remain largely unclear, even though environmental and genetic factors have been suggested to play a role. In order to study the effect of birth seasons on infant sleep architecture, 85 healthy 1-month-old infants underwent an overnight polysomnography (PSG). The PSGs were conducted in 2011–2013. The cohort was divided into four subgroups according to the amount of seasonal light at the time of birth, with each group covering a period of approximately three months. The groups were labeled IL (increasing light), L (light), ID (increasing darkness), and D (dark), corresponding to spring, summer, autumn, and winter, respectively. We found the amount of stage R sleep (precursor of REM sleep, formerly active sleep) to be the highest in infants born in summer, whereas infants born in winter presented the smallest amount of stage R sleep. Infants born in summer presented the smallest amount of stage T sleep (transitional sleep), while stage T sleep was most abundant in infants born in winter. In addition, infants born in summer showed the shortest total sleep time (TST) and the smallest number of awakenings during the study night. This was the first PSG study to find out that birth season modifies the sleep architecture of infants.

KEYWORDS:

• Polysomnography
• infant sleep
• infant polysomnography
• birth season
• seasonality
• stage R sleep
• stage T sleep

Acknowledgments

We thank Tytti Koskelo, who organized and performed the recordings.

Disclosure of interest

The authors report no conflict of interest.

Additional information

Funding

The study was funded by Academy of Finland, Grant no. 134880, and by the Competitive State Research Financing of the Expert Responsibility area of Tampere University Hospital, Grant nos. [9R007, 9R004, 9S007, 9S058 and 9P013].