Polysomnographic Plethysmography Excursions are Reduced in Obese Elderly Men

Area of Science:

• Sleep Medicine
• Respiratory Physiology
• Biomedical Engineering

Background:

• Sleep apnea, characterized by breathing cessation, includes obstructive (OSA) and central (CSA) subtypes requiring distinct treatments.
• Polysomnography (PSG) with plethysmography belts differentiates OSA and CSA by analyzing thoracic and abdominal movements.
• Inter-rater variability in manual PSG interpretation, particularly for CSA, poses diagnostic challenges.

Purpose of the Study:

• To investigate the hypothesis that increased body mass index (BMI) leads to reduced belt signal excursions, potentially increasing false CSA classifications.
• To quantify the association between BMI and respiratory movement signal amplitude during sleep.

Main Methods:

• Analysis of plethysmography belt signals from 2833 subjects in the MrOS Sleep Study.
• Calculation of the signal envelope and extraction of mean excursion values for thoracic and abdominal belts.
• Linear regression analysis to assess the relationship between BMI and signal excursions during REM and non-REM sleep.

Main Results:

• Increased BMI was significantly associated with lower thoracic and abdominal belt signal excursions during both REM and non-REM sleep.
• Quantified negative correlations between BMI and signal amplitude per unit increase in BMI were observed for both thoracic and abdominal signals.

Conclusions:

• Elevated BMI reduces respiratory movement signal amplitude during event-free sleep.
• Higher BMI complicates the distinction between OSA and CSA events using current PSG belt signal analysis.
• This finding has significant implications for accurate diagnosis and appropriate treatment selection in sleep apnea patients with obesity.