FAST-COMPUTED TOMOGRAPHY-EVALUATION OF AGE-RELATED-CHANGES IN UPPER AIRWAY STRUCTURE AND FUNCTION IN NORMAL MEN

The reasons for the increased prevalence of snoring and sleep-disordered breathing in elderly adults are not clear. We hypothesized that age-related reductions in upper airway (UA) size, increased UA collapsibility, and/or inadequate compensatory action of the UA dilator muscles were contributory factors. Fast-computed tomography (CT) was used to examine UA size at FRC and atmospheric pressure, as well as its collapsibility and distensibility in response to negative and positive UA pressures actively generated by the subjects at FRC. The electromyographic activity of the genioglossal muscle group (EMGgg) was recorded to assess UA dilator muscle response. Thirty adult men with normal overnight polysomnography (mean AHI = 4 +/- 1/h) were studied, and three subgroups of 10 subjects each, young (20-39), middle-age (40-59), and old (60-79), were compared. Unexpectedly, minimal UA cross-sectional area (A(min)) at FRC and atmospheric pressure was larger in the old group than in the young group (73 +/- 9 versus 49 +/- 7 mm2, p = 0.04). In response to negative UA pressures of -10 and -50 cm H2O, there were no significant age group differences in A(min), indicating that no age-related increase in UA collapsibility was present. Although no significant difference in tonic EMGgg activity at FRC and atmospheric pressure was detected between groups, the old group demonstrated greater EMGgg activity than did the younger age groups in response to negative UA pressure loading (p < 0.05). This finding indicated increased compensatory UA dilator muscle activity in response to negative pressures in the older subjects. Because the elderly men in this study were selected for the absence of snoring and sleep-disordered breathing, the anatomic enlargement and increased EMGgg response to negative UA pressures may have acted in concert to protect these older men from demonstrating disordered breathing during sleep.