The paper “Modelling changes in sleep timing and duration across the lifespan: changes in circadian rhythmicity or sleep homeostasis?” by Anne Skeldon, Gianne Derks,  and Derk-Jan Dijk (Surrey Sleep Research Centre) has been accepted for publication in the journal Sleep Medicine Reviews.  Sleep patterns change across the lifespan.  For example, a delay in sleep timing is seen in adolescence, followed by a gradual drift to earlier timing during healthy aging.  Using mathematical models, the paper shows how data for sleep timing and sleep duration from ages 10 to 70 can be explained via two different biological mechanisms.