Swallowing Patterns Differ Between Healthy Subjects and Patients with Sleep Apnea

ORLANDO, FL-Individuals identified with sleep apnea appear to have a different pattern of deglutition when they are sleeping than do healthy subjects, say researchers who specialize in swallowing studies.

In particular, doctors in Japan determined that in stage 2-a light sleep stage, characterized by peaks and valleys in polysomnographic tests-sleep apnea patients swallow about six times an hour, whereas healthy subjects swallow about twice an hour (p < 0.01).

The new research, presented during the 88th annual meeting of the American Broncho-Esophagological Association (ABEA) conducted at the Combined Otolaryngology Spring Meeting, also showed that apnea patients tended to swallow more in stage 3 sleep-a deep sleep stage-than do healthy subjects.

Kiminori Sato, MD, PhD, Professor of Otolaryngology-Head and Neck Surgery at Kurume University School of Medicine in Japan, who conducted the research, said that in stage 3, apnea patients swallowed about three times an hour, compared with 0.3 times an hour among healthy subjects. The difference was not statistically significant, however, he said.

Deglutition was infrequent and displayed a unique pattern in patients with obstructive sleep apnea syndrome, Dr. Sato said in his presentation, which received a Broyles-Maloney Honorable Mention award from the ABEA. The deeper the sleep stage, the lower the mean deglutition frequency.

Among healthy individuals, swallowing dropped rapidly as individuals entered deeper sleep stages: 7.2 swallows an hour in stage 1; 2.0 swallows an hour in stage 2; 0.3 swallows an hour in stage 3; and no swallowing in stage 4.

However, Dr. Sato noted that in the sleep apnea patients, swallowing occurred 6.2 times an hour in stage 1; 6.0 times an hour in stage 2; 3.0 times an hour in stage 3; and none in stage 4.

He noted that swallowing in sleep apnea patients appeared to occur often during periods of arousal, as noted with time-matched recordings of polysomnography and surface electromyography of the thyrohyoid and suprahyoid muscles, which are involved in swallowing.

Importance of the Study

This is important and fascinating work, said Peter J. Koltai, MD, Professor of Otolaryngology at Stanford University School of Medicine in California. The study provides insights into what occurs during sleep.

For example, Dr. Koltai asked the researcher what happened to saliva production during sleep. Dr. Sato noted that saliva production decreases. That’s a good thing, said Dr. Koltai, and explains why we don’t drown in our own saliva while we sleep.

Dr. Koltai said that how Dr. Sato’s work will assist in the diagnosis and/or treatment of patients with sleep apnea will require further study.