Impact of the visceral adipose tissue on respiratory and bone variables in patients with untreated mild-to-severe obstructive sleep apnoea

<bold>Background:</bold> Obstructive sleep apnoea (OSA) involves especially obese patients and causes systemic organ damage. Little is known about the impact of body fat distribution. <bold>Objective:</bold> To evaluate the impact of the visceral adipose tissue (VAT) on respiratory and bone variables. <bold>Methods:</bold> In our prospective study, 49 untreated mild-to-severe OSA patients underwent dual-energy X-ray absorptiometry. Data about polygraphy 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 (nVAT) and increased (iVAT). <bold>Results:</bold> 63% of patients were iVAT. Compared with nVAT, iVAT patients had a higher prevalence of arterial hypertension (52% vs 22%) and diabetes (32% vs 6%) and higher values of nocturnal desaturation (median 4.6% vs 3.7%; p=0.002). Patients with iVAT had, in comparison to nVAT, lower values of the lumbar spine trabecular bone score (TBS) L1-L4 (mean 1.24 vs 1.39; p<0.001), T-score (mean -1.82 vs −0.52; p<0.001) and Z-score (mean −0.35 vs 0.75; p=0.002). Furthermore, altered values of the TBS Z-score were associated with vertebral fractures. Finally, in two linear regression models, adjusted for age. sex and severity of OSA, VAT index predicted nocturnal desaturation (β 2.26; 95% CI 0.45 to 4.07; t 2.52; p=0.016) and TBS lumbar spine L1-L4 (β −0.43; 95% CI −0.54 to −0.31; t -7.33; p<0.001). <bold>Conclusion:</bold> In OSA patients, VAT impacts nocturnal desaturation and alters the bone microarchitecture. Some considerations should be made on the role of VAT as a metabolically active tissue.