Summary
This Finnish birth cohort study using home polysomnography found that seasonal light variation significantly affects sleep architecture in infants, with the lightest season shortening night sleep at 1 month and spring light increase degrading both macro- and microstructure of sleep at 8 months. Seasonal effects diminished by toddler age (24 months), suggesting that lighting environment design in nurseries and homes should account for seasonal light exposure, particularly during spring transitions and daylight saving time changes.
Key Findings
- Summer-born infants at 1 month slept shorter nights than autumn-born infants, had more R-sleep (REM equivalent) than winter-born, and less T-sleep (immature transitional sleep) than autumn- and winter-born infants.
- At 8 months, infants in spring slept less deep sleep and more light NREM sleep than in autumn, and had more nocturnal awakenings in spring vs. autumn.
- Daylight saving time transition in spring further degraded sleep quality in 8-month-old infants.
- Sleep spindle frequency activity (SFA) was lower in spring vs. darker seasons at 8 months, and slow-wave activity (SWA) was higher in winter than spring at 8 months.
- At 24 months, seasonal effects on sleep microstructure were minimal, with SWA only slightly lower in winter vs. autumn, suggesting seasonal light sensitivity decreases with age.
- First study to demonstrate in children (8 and 24 months) that sleep spindle activity decreases toward the end of the night, a pattern opposite to that observed in adults, possibly reflecting immature thalamocortical development.
Categories
Sleep & Circadian Health: Examines how seasonal variation in ambient light in Finland affects sleep architecture and duration in infants and toddlers using polysomnography.
Neonatal Care: Investigates seasonal light effects on sleep structure (REM, NREM, slow-wave activity, sleep spindles) in infants aged 1, 8, and 24 months.
Author(s)
A Kärki
Publication Year
2023
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