Obstructive sleep apnea syndrome and autonomic dysfunction.

Area of Science:

• Physiology
• Sleep Medicine
• Autonomic Neuroscience

Background:

• The autonomic nervous system (ANS) plays a crucial role in maintaining bodily homeostasis and responding to stressors.
• Obstructive sleep apnea (OSA) is increasingly recognized for its impact on physiological systems.
• Previous research has indicated autonomic alterations in OSA patients, primarily focusing on cardiovascular effects.

Purpose of the Study:

• To explore the multifaceted impact of obstructive sleep apnea (OSA) on the autonomic nervous system (ANS).
• To review existing methodologies for assessing ANS function in OSA patients.
• To highlight the need for a broader understanding of ANS involvement beyond cardiovascular consequences.

Main Methods:

• Review of studies employing microneurography for direct ANS function assessment.
• Analysis of baroreflex sensitivity (BRS) using sequence and cross-spectral methods.
• Evaluation of heart rate variability (HRV) in time and frequency domains during sleep and wakefulness.
• Inclusion of conventional laboratory tests like the cold pressor test, hand grip test, and urinary catecholamine excretion measurements.

Main Results:

• Consistent evidence of ANS alterations in OSA patients, notably sympathetic overactivity.
• Demonstration of both acute (during apnea events) and chronic (daytime) sympathetic overactivity.
• Indication of a dose-response relationship between OSA severity and sympathetic overactivity.
• Evidence suggesting reversibility of sympathetic overactivity with OSA treatment.

Conclusions:

• Autonomic dysfunction, particularly sympathetic overactivity, is a significant consequence of obstructive sleep apnea.
• The observed autonomic alterations are implicated in the cardiovascular complications associated with OSA.
• Further research is required to fully elucidate the short- and long-term effects of sleep-disordered breathing on the broader functions regulated by the ANS.