Impaired swallowing reflex in patients with obstructive sleep apnea syndrome

The swallowing reflex is well coordinated with breathing patterns in normal humans. However, patients with obstructive sleep apnea syndrome (OSAS) may have a swallowing disorder that reflects the abnormal function of nerves and muscles in the suprapharynx.

To examine the relationship between the swallowing function and sleep-disordered breathing in patients with OSAS.

Twenty patients with OSAS with a mean (+/-SD) age of 53.4+/-8.9 years old, and 20 age-matched control subjects with a mean age of 51.4+/-9.1 years old.

OSAS was diagnosed using the recordings of overnight polysomnography. The swallowing function in the subject was tested using a swallowing provocation test. The swallowing reflex was determined according to the following criteria: latent time (LT), the time following a bolus injection of distilled water at the suprapharynx to the onset of swallowing; inspiratory suppression time (IST), the time from the termination of swallowing to the next onset of inspiration; and threshold volume, the minimum volume of water (range, 0.4 to 2 mL) that could evoke the swallowing response.

Whereas the LT values in patients with OSAS were larger than the LT values in the control subjects, the IST values (which may reflect the switching mechanism from deglutition apnea to breathing) were actually shorter. In addition, a greater bolus volume was necessary to elicit swallowing in patients with OSAS than was necessary in the control subjects.

Patients with OSAS are likely to exhibit an impaired swallowing reflex, probably due to the perturbed neural and muscular function of the upper airways.