Obstructive sleep apnea (OSA) could contribute to mood worsening in patients with OSA and chronic insomnia (CI).
Obstructive sleep apnea (OSA) worsens the abnormalities of sleep microstructure and the autonomic nervous dysfunction in patients with chronic insomnia (CI), and such dysfunction of the autonomic nervous system could contribute to mood worsening in patients with CI-OSA, according to a study published in Nature and Science of Sleep.
This study analyzed the correlation between sleep microstructure, autonomic nervous system activity, and neuropsychological characteristics in patients with both CI and OSA.
“Comorbidity [of OSA and CI] not only increases the incidence of both diseases but also increases the severity of diseases. It has also been found that patients with moderate and severe OSA have a lower incidence of insomnia compared with those with mild OSA or those without OSA,” described the study authors.
First, a total of 45 patients with CI and OSA, 46 patients with CI and 22 match healthy control subjects (controls) were enrolled. Patients with both CI and OSA were divided into 2 groups: mild OSA and moderate-to-severe OSA. Every participant completed neuropsychological tests that included the Hamilton Depression and Anxiety Scales (HAMD and HAMA), the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), the Epworth Sleepiness Scale (ESS), and the Mini-mental State Examination (MMSE). The PSM-100A examined the autonomic nervous system activity and sleep microstructure.
Then, patients with CI-OSA showed higher scores on the PSQI, ESS, ISI, HAMA, and HAMD than controls and patients with CI (all P < .01). The patients with CI-OSA had a lower proportion of stable sleep, and REM sleep and a greater proportion of unstable sleep ratio (all P < .01) than controls and patients with CI (all P < .01). The patients with CI-OSA possessed higher ratios of low frequency power (LF) and LF/high frequency power (HF), and lower ratios of HF and pNN50 (a measure of heart rate variability) (all P < .01) than controls and patients with CI (all P < .01). Compared to those with CI and mild OSA, the patients with CI and moderate-to-severe OSA presented with greater ESS scores, greater ratios of LF and LF/HF, and lower ratios of HF (all P < .05).
“In patients with CI-OSA, higher HAMD scores were correlated with decreased MMSE scores (r = –.678, P < .01). A higher LF ratio was correlated with higher HAMD and HAMA scores (r = .321, P = .031, r = .449, P = .002), and a higher HF ratio was correlated with lower HAMD and HAMA scores (r = –.321, P = .031, r = .449, P = .002),” emphasized the authors.
In this study’s findings, patients who had CI-OSA had more severe sleep structure disorders in a PSM-100A examination, consistent with previous findings that were expressed as decreases in REM sleep and stable sleep, with increases in unstable sleep. Additionally, a significant statistical difference in sleep structure was seen across groups with different apnea-hypopnea index (AHI) levels.
It was also found that patients who had OSA with insomnia had poorer sleep quality and cognition, more sleepiness, depression, and anxiety than healthy subjects and insomnia patients, aligning with previous studies. As AHI increased, such symptoms became worse.
Other previous studies have found that hypoxia time caused by sleep fragmentation in OSA is positively correlated with the severity of depression.
“As the severity of OSA increased, the autonomic nervous dysfunction was aggravated,” discussed the authors as another correlation.
LF/HF was used to study the balance state of tension between sympathetic and parasympathetic tone, which also indicated that the autonomic nervous imbalance of patients with comorbidities is associated to their emotional state.
“The excessive hyperactivity of sympathetic nerves can cause anxiety and depression, which further exacerbate autonomic nervous function disorders,” continued the authors.
One limitation of this study was that the sample size was small, and the findings need to be verified in a larger sample. Moreover, more patients need to be recruited in the future to advance the subgroup analysis.
“In conclusion, OSA exacerbates the abnormalities of sleep microstructure and the autonomic nervous dysfunction in CI patients. Dysfunction of the autonomic nervous system could contribute to mood deterioration in CI with OSA patients. Professionals should enhance the awareness of OSA in chronic insomnia patients with the aim of improving the mood and the autonomic nervous function,” wrote the authors.
Wan Y, Lv M, Zhou K, et al. Mood disorders are correlated with autonomic nervous function in chronic insomnia patients with OSA. Nat Sci Sleep. 2023;15:511-522. doi.org/10.2147/NSS.S396773