Impact of the visceral adipose tissue on bone quality in patients with untreated mild-to-severe obstructive sleep apnea

Obstructive sleep apnea (OSA) predominantly affects patients who are obese and causes systemic organ damage. Little is known about the relationship between fat distribution and bone impairment in these patients. We aimed to evaluate the impact of the visceral adipose tissue (VAT) on the bone quality of patients with OSA. In our prospective study, 49 untreated patients with mild-to-severe OSA underwent dual-energy X-ray absorptiometry. Polygraphy data were also collected. According to the recent reference values for European adults, patients were divided by the sex-related threshold of the VAT index into two categories: VAT index within limits (normal VAT [nVAT]) and increased VAT (iVAT). In all, 63% of the patients were in the iVAT category. Compared to patients with nVAT, those with iVAT had a higher prevalence of arterial hypertension (52% versus 22%) and diabetes (32% versus 6%), and higher values of mean nocturnal desaturation. Patients with iVAT had, in comparison to those with nVAT, lower values of the lumbar spine trabecular bone score (TBS; mean 1.24 versus 1.39; p < 0.001), TBS T-score (mean -1.82 versus -0.52; p < 0.001) and TBS Z-score (mean -0.35 versus 0.75; p = 0.002). Moreover, a close association was present between the VAT index and TBS lumbar spine L1-L4 (r(2) linear 0.573; p < 0.001), and altered values of the TBS Z-score were associated with the severity of vertebral fractures. Finally, in a linear regression-adjusted model, the VAT index predicted TBS lumbar spine L1-L4 (beta -0.323; p < 0.001). In patients with OSA VAT impacts bone quality. In these patients, the role of VAT as a metabolically active tissue should be considered.