Relationship between overnight rostral fluid shift and Obstructive Sleep Apnea in nonobese men.
Level 4 - case-series / case-control
Cross-sectional physiological observational study without an intervention or control group
PubMed 19011149 · doi:10.1164/rccm.200807-1076OC
What was done
In 23 nonobese men referred for polysomnography for suspected obstructive sleep apnea, investigators measured changes in leg fluid volume and neck circumference from bedtime to morning, recorded time spent sitting during the previous day, and evaluated their associations with the apnea-hypopnea index (AHI).
What was found
Overnight decrease in leg fluid volume correlated strongly with higher AHI (r = -0.773, P < 0.001), greater overnight increase in neck circumference (r = -0.792, P < 0.001), and longer daytime sitting time (r = -0.588, P = 0.003). In multivariate analysis, overnight changes in leg fluid volume and neck circumference were the only significant independent correlates of AHI, explaining 68% of its variability.
Why it matters
These findings suggest that dependent fluid accumulation from daytime sitting and its subsequent overnight rostral shift to the neck may contribute to pharyngeal obstruction and sleep apnea pathogenesis independently of obesity.
Limits
The sample size was very small (n = 23) and limited exclusively to nonobese men, precluding generalization to women, obese individuals, or broader populations. The observational, correlational design cannot establish a causal link between fluid redistribution and upper airway collapse.
Cited by
- supports When lying down horizontally, fluid shifts rostrally into the neck, contributing to upper airway obstruction in sleep apnea.