Effects of low-density lipoprotein cholesterol on sleep apnea: Insights from a rat model of cardiovascular autonomic dysregulation

Introduction: The levels of low-density lipoprotein (LDL) cholesterol in plasma are important risk factors for coronary heart disease. Several reports suggest that elevated plasma cholesterol is associated with cardiac arrhythmias. In a subsequent study investigating LDL cholesterol levels and the frequency of LDL cholesterol measurements, a positive correlation was observed between the severity of sleep apnea and visit-to-visit LDL cholesterol variability. Our objective was to assess the effects of hypercholesterolemia on cardiac autonomic activity, disordered sleep patterns, and increased incidence of arrhythmias in freely moving rats. Methods: Wireless transmission of polysomnographic recordings was performed in control and high cholesterol male rats during normal daytime sleep. Spectral analyses were conducted on the electroencephalogram and electromyogram (EMG) recordings to distinguish active waking, quiet sleep, and paradoxical sleep. Heart rate variability power spectrum analysis was used to measure cardiac autonomic activity. Results: The high cholesterol group exhibited a higher low-frequency (LF)/high-frequency (HF) power ratio during all sleep stages compared to the control group. Additionally, the frequency of sleep interruptions was increased in the high cholesterol group compared to the control group. Conclusions: Our results show significant sleep fragmentation with sympathetic hyperactivity after exposure to high cholesterol. This indicates that high cholesterol may increase the risk of sleep apnea and poor sleep quality by disrupting autonomic homeostasis.