Difficulty in initiating sleep is associated with poor morning cardiovascular function.

Area of Science:

• Cardiovascular Physiology
• Sleep Medicine
• Autonomic Nervous System Function

Background:

• Insomnia, particularly sleep-onset insomnia, is linked to hypertension and cardiovascular events.
• The specific impact of sleep-onset insomnia on morning cardiovascular regulation remains unclear.

Purpose of the Study:

• To investigate morning cardiovascular function in individuals with sleep-onset insomnia.
• To analyze heart rate variability (HRV), blood pressure variability, and baroreflex sensitivity post-awakening.

Main Methods:

• Polysomnography to assess sleep quality in 15 good sleepers and 13 individuals with sleep-onset insomnia.
• 10-minute continuous blood pressure and heart rate recordings immediately after morning awakening.
• Analysis of HRV, blood pressure variability, and baroreflex sensitivity.

Main Results:

• Individuals with sleep-onset insomnia exhibited reduced vagal tone (lower HRV total power and high frequency) post-awakening.
• Elevated systolic and diastolic blood pressure slopes and blunted baroreflex sensitivity were observed in the insomnia group.
• No significant differences in sympathetic-related activity were found between groups.

Conclusions:

• Sleep-onset insomnia independently affects morning cardiovascular function.
• Weakened vagal modulation and blunted baroreflex sensitivity are characteristic of this insomnia subtype.
• The parasympathetic nervous system's role in cardiovascular regulation is significantly impacted by difficulty initiating sleep.