FIGURE 2.22 Total sleep and proportion of REM and non-REM sleep across the life span Newborns average a total of 16 hours of sleep, roughly half of it in REM sleep. The total amount of sleep declines sharply throughout early childhood and continues to decline much more slowly throughout life. From adolescence on, REM sleep constitutes only about 20% of total sleep time. (Adapted from Roffwarg et al., 1966, and from a later revision by these authors)