Abstract Essential hypertension involves complex cardiovascular regulation. The autonomic nervous system function fluctuates throughout the sleep–wake cycle and changes with advancing age. However, the precise role of the autonomic nervous system in the development of hypertension during aging remains unclear. In this study, we characterized autonomic function during the sleep–wake cycle in different age groups with essential hypertension. This study included 97 men (53 with and 44 without hypertension) aged 30–79 years. They were stratified by age into young (