When most people think of obstructive sleep apnea (OSA), they picture loud snoring, restless nights, and daytime fatigue. But new research suggests the condition may be affecting the body in a less obvious way — by changing the composition of your muscles.

A recent study published in Sleep and Breathing found that people with obstructive sleep apnea often have muscles that appear larger but may actually be less healthy. Researchers discovered that individuals with OSA tend to have a higher skeletal muscle index (SMI), meaning they have more muscle mass relative to their height. However, those same muscles often show lower density, which may indicate higher levels of fat infiltration.

In simple terms, people with sleep apnea may look more muscular, but their muscles could be weaker and less efficient than they appear.

What the Researchers Found

The study analyzed data from 209 adults who participated in overnight sleep evaluations and underwent chest or abdominal CT scans. Compared to people without sleep apnea, those with OSA were generally older, more likely to be male, and had higher body weights. They were also more likely to experience high blood pressure, cardiovascular disease, and lower oxygen levels while sleeping.

Researchers found a clear association between sleep apnea and increased muscle size. However, reduced muscle density was more strongly linked to aging and obesity than to sleep apnea alone.

The more severe a person’s sleep apnea, the more likely they were to have larger but less dense muscles — a pattern that may reflect declining muscle quality.

Why Muscle Quality Matters

Dr. Wendy Troxel, a licensed clinical psychologist and sleep expert who was not involved in the study, explained that muscle density is an important marker of overall muscle health.

According to Troxel, muscles infiltrated with fat may not function as effectively, potentially affecting both strength and metabolism. This pattern resembles a condition known as sarcopenia, where muscles become weaker and less efficient over time, even when muscle size remains relatively stable.

The findings suggest that sleep apnea may be part of a broader metabolic health picture rather than simply a nighttime breathing disorder.

Age and Weight Play a Major Role

While sleep apnea showed a connection to muscle quality, researchers found that age and obesity had an even stronger impact.

Adults over the age of 60 and individuals with a body mass index (BMI) above 30 showed significantly greater reductions in muscle density than could be explained by sleep apnea alone. This suggests that aging and excess weight remain major contributors to declining muscle health.

Lead researcher Ariel Tarasiuk of Ben-Gurion University of the Negev described the findings as somewhat paradoxical.

“Age and obesity appeared to have a stronger influence on muscle health than sleep apnea itself,” he noted. “While sleep apnea may play a role, it is unlikely to be the primary factor driving these changes.”

What This Means for People With Sleep Apnea

The study reinforces the idea that sleep apnea affects far more than sleep quality.

Untreated OSA has already been linked to a range of health concerns, including heart disease, high blood pressure, and metabolic disorders. This new research suggests muscle health may also be part of the equation.

Experts emphasize that treatment should go beyond simply reducing snoring. Continuous Positive Airway Pressure (CPAP) therapy remains one of the most effective treatments for OSA, helping improve breathing and oxygen levels during sleep. However, researchers stress that maintaining a healthy weight and staying physically active are equally important for preserving muscle quality and reducing sleep apnea severity.

As Tarasiuk explained, treating sleep apnea is ultimately about protecting long-term health—not just getting a better night’s sleep.

Looking Ahead

The researchers caution that the findings have limitations. The study was conducted at a single medical center and did not account for lifestyle factors such as exercise habits, diet, smoking, or alcohol consumption, all of which can influence muscle health.

Future studies involving larger and more diverse populations will help determine how sleep apnea contributes to changes in muscle quality over time and whether treatments like CPAP can help reverse those effects.

For now, the takeaway is clear: sleep apnea may be affecting your body in ways you can’t see. If you experience symptoms such as loud snoring, frequent nighttime awakenings, or excessive daytime fatigue, seeking evaluation and treatment could benefit much more than your sleep.