Each line represents one participant’s change in sleep from visit 1 to visit 2. The pre-to-post increase in total sleep time was significant but small, t(2642) = 3.12, p = .002, d = 0.06, whereas the increase in wake after sleep onset was large, t(2642) = 20.63, p < .001, d = 0.40. SWS declined over time by 9.0%, t(2642) = 8.51, p < .001, d = 0.17, whereas REM sleep actually increased over time by 3.6%, t(2642) = 3.99, p < .001, d = 0.08 (greater age at visits 1 and 2 was cross-sectionally associated with decreased REM, rs = −.220 and −.295).