Associations of sleep architecture, sleep fragmentation, and hypoxia-related parameters with cognitive frailty in older patients with hypertension and obstructive sleep apnea: a cross-sectional study

To investigate the associations of sleep architecture, sleep fragmentation, and nocturnal hypoxia-related parameters with cognitive frailty (CF) in older patients with hypertension and obstructive sleep apnea (OSA). In this single-center cross-sectional study, 240 hospitalized patients aged ≥ 60 years with hypertension and OSA confirmed by polysomnography (PSG) were enrolled between January 2025 and January 2026. Participants were classified into a CF group ( n = 83) and a non-CF group ( n = 157). Demographic and clinical data were collected. Cognitive frailty was assessed using the Chinese version of the Montreal Cognitive Assessment and the Fried Frailty Phenotype. PSG variables included total sleep time, sleep-stage durations, arousal index, apnea–hypopnea index, oxygen desaturation index, minimum oxygen saturation, and mean oxygen saturation. Multivariable logistic regression was performed to identify factors independently associated with CF. Compared with the non-CF group, the CF group had shorter N3 sleep duration, lower minimum oxygen saturation, and a higher arousal index. After adjustment for sex, age, years of education, and body mass index, N3 sleep duration (OR = 0.988, 95% CI: 0.981–0.996, P = 0.002) and minimum oxygen saturation (OR = 0.945, 95% CI: 0.914–0.977, P < 0.001) were independently negatively associated with CF, whereas arousal index (OR = 1.016, 95% CI: 1.005–1.027, P = 0.005) was independently positively associated with CF. Age was also independently associated with CF. Reduced N3 sleep duration, lower minimum oxygen saturation, and higher arousal index were associated with CF in older patients with hypertension and OSA, supporting the need for prospective studies to clarify temporal relationships.