A sleep disorder affecting millions of Americans may be quietly changing the quality of their muscles, not just their mass, according to new research using CT scans.
Quick Take
- Obstructive sleep apnea causes breathing to stop and start repeatedly during sleep, and it affects tens of millions of adults in the United States.
- A study of 209 patients found people with more severe sleep apnea had higher skeletal muscle mass but lower muscle density.
- Lower muscle density often means fat has built up inside the muscle tissue itself, a sign of poor muscle quality.
- Separate studies on hundreds more patients found the same pattern, though age and body weight also play a role.
What Researchers Found In The CT Scans
Researchers studied just over 200 adults who had both a sleep study and a CT scan on file. Instead of only measuring how much muscle a person had, they also measured muscle density, which shows how much fat sits inside the muscle tissue. People with worse sleep apnea showed a clear pattern: more muscle area, but muscle that was less dense.
The research team, working with Ben-Gurion University of the Negev and Soroka University Medical Centre, found sleep apnea was tied to lower skeletal muscle density even after accounting for other factors. Their study appeared in the journal Sleep and Breathing and described this as a significant link between the disorder and muscle quality.
Why More Muscle Mass Isn’t Good News Here
At first glance, higher muscle mass sounds like a good thing. But density matters more than size when it comes to how well a muscle actually works. Fat creeping into muscle tissue, sometimes called myosteatosis, weakens strength and function even when the muscle looks bigger on a scan. That mismatch is exactly what researchers found in sleep apnea patients.
A 2018 study published in Scientific Reports backs this up. It found the apnea-hypopnea index, a measure of how often breathing stops during sleep, rose alongside skeletal muscle index while muscle density fell in both men and women. The direction of the pattern matched later, larger studies almost exactly.
The Pattern Showing Up Across Multiple Studies
This is not a single, isolated finding. A study of 334 people suspected of having sleep apnea found the same positive link between apnea severity and skeletal muscle loss markers on CT scans. Another analysis of fat, bone, and muscle indices found pectoralis muscle density dropped as apnea severity and oxygen desaturation increased.
Researchers caution the story is not simple cause and effect. The 2018 study noted the muscle density relationship was not fully independent of obesity, and a larger 209-person study found the density link weakened once age and body weight were factored in. Body size and aging clearly influence the picture alongside sleep apnea itself.
What This Means For People Living With Sleep Apnea
A Fox News report on the same body of research noted that patients with obstructive sleep apnea tend to show a higher muscle mass index paired with lower muscle density, a combination that signals declining muscle quality rather than improved strength. For patients already managing apnea with devices like CPAP machines, this adds another reason to take treatment seriously.
Sleep apnea already carries known risks for heart health, blood pressure, and daytime alertness. This research adds muscle quality to that list. For the roughly 30 million American adults estimated to have some form of sleep apnea, the message is straightforward: poor sleep may be doing more than draining energy. It could be changing the body’s muscle composition in ways that standard scales and mirrors simply cannot show.
Sources:
mindbodygreen.com, pmc.ncbi.nlm.nih.gov, nature.com, bgu.ac.il, cris.bgu.ac.il
