Figure 2.

Kaplan-Meier survival curves for cycle, NREM, and REM sleep episode durations. Cycle survival increased with age (A) (bootstrapped log-rank test, p = 0.01) due to increases in NREM sleep episode duration with age (B) (bootstrapped log rank test, p < 0.01), but the survival of REM sleep episodes showed no age-related change (C) (bootstrapped log rank test, p = 0.73).