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Development of sleep: Statistical properties and the role of movement-related neural events

Final Activity Report Summary - SLEEP DEVELOPMENT (Development of sleep: Statistical properties and the role of movement-related neural events)

Studies in adult mammals (rats, cats, mice, and humans) have revealed a surprising statistical regularity in the duration of sleep and wake bouts. Wake bout durations exhibit a power-law distribution with nearly identical scaling exponent across these four species, whereas sleep bout durations exhibit an exponential distribution with a characteristic time scale. These data suggest that bout distributions may offer novel metrics to make comparisons of human and animal sleep-wake data. Studies in rodents have found a developmental trajectory in which sleep bout durations are exponentially distributed at all ages examined, with a developmentally increasing characteristic timescale reflecting sleep consolidation. Wake bouts, on the other hand, exhibit exponential distributions early in ontogeny with a clear power-law emerging only at the older ages.

In order to test the generalisability of these findings, we examined the distributions of sleep and wake bouts during the night in a healthy human sample - from premature infants to 70-year-olds. We find that sleep bout durations exhibit exponential distributions at all ages tested, except for the youngest (premature infants). Moreover, sleep bouts elongate over the first years. Wake bouts shorten during this time, but elongate again with increasing age. Most notably, wake bouts exhibit a power-law distribution only during a restricted time window during adulthood.

The current findings, therefore, indicate that the developmental trajectory of human sleep-wake cycles does not map well onto those of rodents. Further development of this method of characterising sleep-wake cycles using bout distribution holds promise for classifying properties of sleep and its disorders, and for tracking developmental milestones across the human life-span.