Objective:

To determine if obstructive sleep apnea (OSA) predicts multiple sclerosis (MS) disease burden independent of obesity, a known risk factor for both OSA and for MS-associated brain atrophy. 

Background:

Recent studies found that patients with MS and OSA had higher body mass index (BMI), more brainstem lesions, and more brain atrophy than patients with MS without OSA. It is currently unknown whether OSA can develop due to MS disease activity alone or if it stems from other established factors like obesity.

Design/Methods:

We collected whole brain volumes (WBV), gray matter volumes (GMV), and WBV and GMV age-normalized percentiles from the MRIs of patients with both MS and OSA. To control for obesity, we categorized patients into two groups: MS and OSA with obesity (BMI ≥ 30) and MS and OSA without obesity (BMI < 30). We utilized multivariable linear regression to assess differences in brain atrophy in these two groups. 

Results:

We identified 39 patients for inclusion in this study: 26 patients with OSA and obesity and 13 patients with OSA without obesity. By multivariable linear regression, we found that non-obese OSA patients had lower WBV (P = 0.027), GMV (P = 0.039), WBV% (P = 0.029), and GMV% (P = 0.048) than obese OSA patients, controlling for MS disease duration, blood pressure, tobacco use, and older age, all risk factors for brain atrophy. 

Conclusions:

OSA is associated with greater brain atrophy independent of obesity in patients with MS.