The influence of aging on pharyngeal collapsibility during sleep

Abstract

Background: Aging increases vulnerability to obstructive sleep apnea (OSA), but the underlying mechanisms remain unclear. Recent data in awake healthy volunteers show a decrease in the genioglossus negative pressure reflex and anatomic compromise with increasing age, suggesting an age-related predisposition to pharyngeal collapse. However, aging effects on pharyngeal collapsibility have not been studied extensively during sleep. We tested the hypotheses that upper airway closing pressure (PCLOSE) and the increase in pharyngeal resistance during sleep (primary outcomes) as well as measures of arousal threshold (secondary outcomes) increase with age.

Methods: We studied 21 healthy individuals (8 women [mean (+/- SD) age, 36 +/- 18 years] and 13 men [mean age, 41 +/- 23 years]) who were between 18 and 75 years of age. During overnight polysomnography, we measured nasal pressure (PMASK) and epiglottic pressure (Pepi) during stage 2 sleep before and after airway occlusion (external valve) until arousal. PCLOSE was defined as the pressure at which PMASK plateaued despite further decreases in PEPI.

Results: Increasing age was correlated with both pharyngeal collapsibility ([PCLOSE] r = 0.69; p < 0.01) and an increase in pharyngeal resistance during sleep (r = 0.56; p < 0.01) independent of body mass index (BMI) and gender. There was no evidence for an effect of age on arousal threshold after airway occlusion during stage 2 sleep.

Conclusions: Older age is associated with increased pharyngeal airway collapsibility during sleep independent of gender and BMI. These data may at least partially explain the mechanisms underlying the predisposition for pharyngeal collapse in the elderly.

Conflict of interest statement

The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Figures

Figure 1

Measurement setup. A face mask covering the nose was sealed with an adhesive elastomer and held in place by head straps. The mask was connected directly to a pneumotachograph, which was connected to a Y-piece containing inspiratory and expiratory valves. The inspiratory port was connected to a pneumatic valve (Hans Rudolph) that could occlude this port while allowing expiration to continue such that airway occlusion could be performed at functional residual capacity.

Figure 2

Typical response to airway occlusion (in a 68-year-old subject). During occlusion, each inspiratory effort produced a decrease in Pmask and Pepi. While Pepi progressively decreased to a minimum value, Pmask separated from Pepi during breaths 2 to 5 as the result of pharyngeal airway collapse. The inflection points (Pclose) of the Pmask trace (vertical lines) were defined as the points at which airway collapse occurred. Note that airway collapse (ie, the plateau in Pmask) does not occur on breath 1. This may be due to a decrease in expiratory lung volume between breaths 1 and 2 (subjects were able to exhale through an expiration valve). Minimum Pepi values became more negative with each subsequent respiratory effort until arousal from sleep occurred. The arousal threshold was defined as the nadir Pepi at the respiratory effort preceding arousal.

Figure 3

Measurement of Pclose from polygraph tracings of Pepi and Pmask. During occlusion of the valve connected to the subject’s nasal mask, Pepi progressively increased to a maximum value, whereas Pmask plateaued as the result of pharyngeal airway occlusion. The intersections between the two dotted lines represent the Pclose values. Top, A: elderly person 75 years of age. Bottom, B: younger person 20 years of age.

Figure 4

Pclose as a function of age. Mean values from 18 persons. Multiple regression analysis revealed that Pclose became less negative with age (r= 0.75; p = 0.011).

Figure 5

Difference in pharyngeal resistance between wakeful-ness and stable stage 2 sleep as a function of age. Data from 20 persons. Multiple regression analysis revealed that the increase in pharyngeal resistance from wakefulness to stable stage 2 sleep was closely related to age (r = 0.87; p < 0.0001).