Sympathetic dominance

Sympathetic dominance describes a chronic shift in autonomic balance toward sustained sympathetic nervous system activation relative to parasympathetic tone, typically reflected in suppressed HRV metrics such as RMSSD and HF power, elevated resting heart rate, and blunted nocturnal vagal withdrawal. Acute sympathetic activation is adaptive, but chronic elevation driven by psychological stress, overtraining, sleep deprivation, or metabolic dysfunction is associated with hypertension, dysregulation of the HPA axis, and accelerated cardiovascular aging. It is not a clinical diagnosis but an operational concept used in longevity and sports science to flag persistently impaired autonomic recovery; interpretation requires ruling out confounders such as dehydration, illness, and measurement artefacts.