When during sleep are symptoms of REM Sleep Behavior Disorder (RBD) most likely to occur?

The symptoms of REM Sleep Behavior Disorder (RBD) are primarily associated with the last REM cycle of sleep. During this stage, individuals may exhibit abnormal behaviors such as acting out dreams, which can involve physical movements, vocalizations, or even aggressive actions.

RBD typically occurs in the later cycles of sleep because REM sleep duration tends to increase with each successive cycle, peaking during the final one. This is when the characteristics of REM sleep, which include muscle atonia and increased brain activity, are most pronounced, but individuals with RBD may experience a failure of this muscle atonia, leading to the manifestation of their dreams through physical actions.

Waking hours and light stages of sleep are not directly related to the manifestations of RBD symptoms, as the disorder is specifically tied to the characteristics of REM sleep. Similarly, the first REM cycle is less likely to see the pronounced behaviors associated with RBD, as the condition typically develops and becomes more prominent in the later stages of sleep when REM cycles are longer and more intense.