In some ways, the throat can be loosely defined as a tube for breathing, swallowing, and speaking. During wakefulness, the muscles that surround the throat have a certain level of activation that keeps the throat open. During sleep, there is a decrease in the level of nerve signals that activate muscles in the body. In the throat, this means that these muscles surrounding the throat are less active, allowing blockage of breathing that defines obstructive sleep apnea (OSA). Multiple studies have demonstrated that individuals with OSA possess structural changes in muscles, including stiffening or a change in fiber type.

A recent study in the medical journal The Laryngoscope examines lipofuscin deposits within the muscles of the sides of the throat (palatopharyngeus and superior pharyngeal constrictor). Lipofuscin is a material that accumulates over time within cells, containing proteins, fats, metal ions, and other residues. Oxidative stress (such as the repeated drops in oxygen levels in OSA) is felt to damage mitochondria (cellular “engines”), and damaged mitochondria are the main contributors to lipofuscin production within the cell. In skeletal muscle (such as the muscles surrounding the throat), the accumulation is permanent, leading to its label as a so-called age pigment. Because lipofuscin takes up space within the cell, it has been suggested that greater amounts of lipfuscin within a cell can interfere with normal cellular function. This is above and beyond the fact that the mitochondria are damaged.

This study from researchers at the University of Sao Paulo in Brazil (including Kristine Fahl and Michel Cahali, an internationally-recognized sleep surgeon) compared non-obese adults with severe OSA to those with mild OSA or primary snoring without OSA. Tissue was obtained from the sides of the throat in all patients during surgery. A variety of staining methods and microscopic analyses showed substantial lipofuscin deposits in the severe OSA group that were 2-3 times as great as in the snoring/mild OSA group.

The bottom line: possible explanation for worsening of OSA over time

This study contributes to our knowledge that OSA is associated with changes in the muscles surrounding the throat. Furthermore, it provides a possible mechanism explaining poor muscle function and the worsening of OSA that occurs over time, separate from weight gain.