REM sleep proportion: an independent predictor of olfactory dysfunction in obstructive sleep apnea hypopnea syndrome

This study aimed to investigate the association between olfactory dysfunction and sleep architecture parameters in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS), identify independent factors influencing olfactory function, and offer novel insights into the multisystemic impact of OSAHS.

Employing a cross-sectional retrospective design, data from 198 patients diagnosed with OSAHS via polysomnography (PSG) from December 1, 2020, to June 30, 2024, were analyzed. Olfactory performance was assessed using the Sniffin' Sticks test kit. Sleep structure parameters, including total sleep time (TST), sleep efficiency (SE), N3 sleep proportion (N3%), rapid eye movement sleep proportion (REM%), apnea-hypopnea index (AHI), and lowest oxygen saturation (LSaO2), were recorded by PSG. Pearson and Spearman correlation analyses were conducted to examine associations between olfactory scores and sleep parameters. Multivariate logistic regression was employed to determine independent predictors for olfactory impairment.

Male patients exhibited a significantly higher proportion in the olfactory dysfunction group (81/131) compared to the normal olfaction group (50/131; p < 0.05). Additionally, the olfactory impairment group showed significantly reduced total microarousals during REM and NREM sleep, N3/TST%, and REM/TST% compared to the normal olfaction group (p < 0.05). Conversely, AHI and wake after sleep onset (WASO) were notably increased in patients with olfactory impairment (p < 0.05). Olfactory threshold (T), discrimination (D), identification (I), and total TDI scores were significantly lower in patients with olfactory dysfunction (p < 0.05). Correlation analyses revealed negative correlations between total TDI scores and age, AHI, and WASO, while positive correlations were observed with TST, SE, total REM sleep microarousals, and REM/TST%. Logistic regression analysis further identified age, AHI, and REM/TST% as independent predictors influencing TDI scores.

Age increase, elevated AHI and decreased REM/TST% are independent influencing factors for the occurrence of olfactory disorders. The decline in olfactory function is significantly associated with a marked reduction in REM sleep. Elderly patients with OSAHS, high AHI and low REM proportion should be the key population for olfactory function screening.