The pathophysiology of obstructive sleep apnea syndrome in women: role of low arousal threshold.

<bold>Background:</bold> Obstructive Sleep Apnea Syndrome (OSAS) results from several pathophysiological mechanisms: one or more impaired anatomical factors with a variable contribution of the functional factors. Low Arousal Threshold (AT) is prevalent in patients with mild disease, non-obese, and poor CPAP adherence. We assumed that for their clinical and polysomnographic features (Bublitz M et al. Life (Basel).2022;12(12):2003), women with OSAS could have low AT as the most prevalent functional factor. <bold>Method:</bold> A retrospective study of patients attending the Pulmonology Unit of the University Hospital of Trieste and Sapienza University of Rome, Italy, was carried out. Low AT was predicted through the polysomnographic score proposed by Edwards et al (AJRCCM. 2014;190(11):1293-1300), which attributes one point for each criterion: (AHI < 30 events/ hour) + (nadir SpO2 > 82.5%) + (hypopnea fraction > 58.3%). A score of ≥ 2 predicts a low AT. We evaluated 175 patients with OSAS, 82 females and 93 males. Each patient had a home sleep apnea test that a sleep expert evaluated. <bold>Results:</bold> Presence of low AT was present in 62.2% of women (51/82) versus 40.8% of men (38/93),(p=0.005). In obese patients: low AT was present in 60.9% of women and 21.6% of men (p<0.01). Stratifying for the severity of OSA, low AT was prevalent in mild disease (91.5% in AHI<15, 57.7 % in AHI >15, and <30 and 5.5% in AHI ≥30). <bold>Conclusion:</bold> This study demonstrated the prevalence of low AT as the main functional factor in the pathophysiology of OSA in women, regardless of obesity. Our results could explain why women are often underdiagnosed and CPAP therapy is not well tolerated.