Sleep monitoring and memory impairment in elderly patients with comorbid insomnia and obstructive sleep apnoea

Objective To investigate the association between sleep parameters and memory impairment in elderly patients with comorbid insomnia and obstructive sleep apnoea (COMISA). Methods From June 2024 to June 2025,86 elderly patients with simple chronic insomnia admitted to the Department of Neurology of Handan First Hospital were selected as the insomnia group, 74 insomnia patients with comorbid obstructive sleep apnea (OSA) as the COMISA group, and 30 elderly people without insomnia received by the Health Examination Department during the same period the control group. All study subjects underwent polysomnography (PSG). Sleep parameters were recorded, including apnea hyponea index (AHI), lowest pulse oxygen saturation (LSpO2), non-rapid eye movement (NREM), rapid eye movement (REM), total sleep time (TST), sleep latency (SL), and sleep efficiency (SE). Pittsburgh sleep quality inventory (PSQI) and insomnia severity index (ISI) were used to evaluate the subjective sleep quality. Montreal cognitive assessment (MoCA) scale was used to evaluate the overall cognitive function, and clinical memory scale (CMS) to evaluate the memory function. SPSS 26.0 was used for data analysis. According to the data type, Chi-square test or one-way analysis of variance was performed for comparison between groups. Pearson correlation coefficient analysis was conducted to analyze the correlations between sleep parameters and CMS scores in the COMSIA group. With the total score of CMS in COMSIA patients as the dependent variable, and multivariate linear regression model was adopted to analyze the factors affecting the total score of CMS. Results The PSQI and ISI scores in the COMISA group and the insomnia group were lower than those in the control group; the SL was higher while the TST, SE and proportion of NREM3 were lower than those in the control group.The AHI in the CMOISA group was higher than that in the insomnia group and the control group. The proportion of REM and LSpO₂ level were lower than those in the insomnia group and the control group. The proportion of NREM3 in the CMOISA group was lower than that in the insomnia group (all P<0.05). The score of MoCA scale and total score and scores of dimensions of CMS in COMISA group and insomnia group were lower than those in control group while the detection rates of mild cognitive impairment (MCI) and memory impairment were higher, and the score of MoCA scale and scores of dimensions and total score of CMS in COMISA group were lower while the detection rates of MCI and memory impairment were higher than those in insomnia group (all P<0.05). Pearson correlation analysis suggested that in the CMOISA group, NREM3 was positively correlated with free recall of pictures and the total score of CMS (r=0.516,0.415; both P<0.001); REM was positively correlated with directed memory score, associative memory score and total CMS (r=0.403,0.407,0.504; all P<0.001); AHI was negatively correlated with associative memory and total CMS (r=0.389,0.398; both P<0.05); and LSpO₂ was positively correlated with total CMS (r=0.431; P<0.001). With total CMS in CMOISA patients as the dependent variable, linear regression analysis results revealed that NREM3 (β=0.146,95%CI 0.012-0.229; P<0.001) and REM (β=0.178,95%CI 0.007-0.184; P<0.001) could positively predict the CMS in COMISA patients, while AHI (β=-0.084,95%CI -0.345--0.009; P<0.001) could negatively predict the CMS in COMISA patients. Conclusion Elderly patients with insomnia and elderly patients with CMOISA show decreased subjective sleep quality and abnormal objective sleep structure. In addition, the overall cognitive function and memory function declined, and patients with CMOISA have more severe abnormal objective sleep structure and a higher degree of impairment in overall cognitive function and memory function. Sleep parameters are factors affecting the memory function in patients with COMISA.