The major confirmation of the relationship between sleep and autonomic nervous system (ANS) is the presence of dynamic synchronous fluctuations in sleep phases and autonomic functions. Nocturnal monitoring of breathing, pulse rate, systemic arterial pressure, and peripheral vasomotor activation discloses autonomic deactivation that, appearing at sleep onset, continues into deep sleep. The increased prevalence of sleep disorders with aging may be influenced by medical co-morbidities and medications that alter sleep architecture. Age-related changes in ANS function are linked to changes in body composition, neuronal loss, neurotransmitter underproduction or reduced receptor function, tissue damage, and hormonal changes. Autonomic function testing may be very helpful to evaluate the extent of autonomic involvement and to monitor the course of the disorder and the response to therapy. The effect of age on sudomotor pathway and control of core temperature is complex and involves different levels of ANS.