Assessment of Abdominal Adiposity in OSA Using Combined PET Imaging and MRI: Impact of Short-Term CPAP

Obesity is a major risk factor for OSA, and visceral adiposity may mediate its cardiometabolic consequences. However, studies evaluating the impact of CPAP on visceral obesity have yielded conflicting results.

What is the relationship between OSA and visceral adipose tissue (VAT) volume and metabolic activity, and how does short-term CPAP therapy modify these measures?

Adults with newly diagnosed, moderate to severe OSA underwent combined [¹⁸F]-fluoro-2-deoxy-D-glucose (FDG) PET imaging and MRI before and after short-term CPAP therapy. Using a novel deep learning approach to segment abdominal adipose compartments, we quantified adipose volumes and metabolic activity using mean standardized uptake values (SUV_mean). The primary outcome was VAT SUV_mean. Secondary outcomes included VAT and subcutaneous adipose tissue (SAT) volume, and VAT to SAT volume ratio. Associations between OSA severity and adipose metrics and CPAP effects were assessed using multivariable regression and linear mixed-effects models.

Among 134 participants, OSA severity was not associated with increased VAT SUV_mean in adjusted analyses (P = .70) and CPAP did not alter VAT metabolic activity significantly after 3 months (P = .66). A modest reduction in VAT to SAT volume ratio (P = .03) was observed after CPAP therapy, despite no changes in weight or total abdominal adipose tissue volume. Although CPAP did not affect VAT volume (P = .09) overall, we observed a significant reduction in VAT volume in patients with obesity (-2.08%; 95% CI, -3.9 to -0.24; P = .03).

In this study, short-term CPAP therapy was not associated with a reduction in VAT metabolic activity, though a modest shift in fat distribution from the visceral to subcutaneous compartment was observed. Notably, patients with obesity had a significant reduction in VAT volume, highlighting potential heterogeneity of treatment effects. Our findings underscore the need for longer-term studies to evaluate how CPAP therapy and, importantly, adjunct weight loss pharmacotherapies may alter fat distribution and visceral adiposity, potentially modifying OSA-related cardiometabolic risk.