Which stage of sleep is characterized by increased heart rate and irregular breathing?

The stage of sleep characterized by increased heart rate and irregular breathing is REM (Rapid Eye Movement) sleep. During this stage, the brain is highly active, resembling wakefulness, and most vivid dreaming occurs. Physiological changes during REM sleep include fluctuations in heart rate and a lack of consistent breathing patterns, with periods of rapid respirations that can be irregular. This distinct activity is attributed to brain function that is similar to an awake state, contrasting with the more stable heart rates and breathing patterns found in NREM sleep stages. NREM stages, particularly the deeper ones, are associated with restorative rest and more regulated physiological states.