Original ArticleEffect of CPAP treatment on residual depressive symptoms in patients with major depression and coexisting sleep apnea: Contribution of daytime sleepiness to residual depressive symptoms
Introduction
Obstructive sleep apnea (OSA) is the most common form of sleep disordered breathing and is characterized by intermittent partial or complete upper airway obstruction during sleep, accompanied with sleep fragmentation and nocturnal hypoxemia. Clinically, OSA is suspected when a patient presents with both loud snoring and excessive daytime sleepiness. OSA has been described to result in daytime sleepiness, impaired quality of life [1], [2], cognitive dysfunction [3], [4], and several psychological changes, such as depression and anxiety [5], [6], [7].
For over two decades, various clinical and epidemiological studies have focused on the relationship between OSA and depression, and elevated rates of depressive symptoms ranging from 20% to 45% have been found in untreated OSA patients [8], [9], [10], [11], [12], [13], [14], [15], although some studies have failed to find positive correlations between OSA and depressive symptoms [16], [17], [18]. Guilleminault et al. reported that 24% of 25 OSA patients had previously seen a psychiatrist for anxiety or depression [8], and Millman et al. observed that 45% of 55 OSA patients had Zung Self-Rating Depression Scale (SDS) scores ⩾50, consistent with depression [11]. Other investigators also observed elevated depression scores on the Minnesota Multiphasic Personality Inventory (MMPI) [9], [12], Profile of Mood States questionnaire (POMS) [14] or Beck Depression Inventory (BDI) [13] in OSA patients.
Various treatment studies have also demonstrated that continuous positive airway pressure (CPAP) therapy resulted in a significant improvement of depressive symptoms in OSA patients using various psychometric tests, such as POMS [14], [19], MMPI [20], SDS [11], and BDI [21], [22], although a few studies have not shown any significant improvements of depressive symptoms [23], [24], [25]. Derderian et al. compared results on the POMS before and after 2 months of CPAP treatment in 7 OSA patients and found a significant drop in Total Mood Disturbance [19]. In the study of Millman et al., 11 OSA patients who received CPAP treatment showed a significant decrease in SDS scores [11]. Means et al. found a significant improvement on BDI scores after 3 months of CPAP treatment in 39 OSA patients [21], and Sánchez et al. observed a significant improvement of BDI scores after 1 and 3 months of CPAP treatment in 51 OSA patients [22]. Ramos Platón et al. underscored the progressive improvement in depression scores on the MMPI scale over the first year of CPAP treatment [20].
Most studies, however, either excluded OSA patients suffering from major depressive disorder (MDD) or their depression scores were even at baseline in a normal range [5], [7]. While the presence of depressive symptoms has been often considered in OSA patients, the presence of OSA has been rarely assessed in MDD patients. Until now, the effect of CPAP treatment on residual depressive symptoms in medicated MDD patients with coexisting OSA has not been examined. Untreated OSA might not only be associated with residual depressive symptoms, but its presence may also be responsible for the failure to respond to antidepressant treatment among MDD patients.
In this study, we evaluated the short-term effect of CPAP treatment on residual depressive symptoms in medicated MDD patients with comorbid OSA. This is perhaps the first preliminary study to assess the degree to which CPAP treatment reduces residual depressive symptoms in patients with continued MDD (despite pharmacotherapy) who also have comorbid OSA. We also analyzed the factors related to improvements of residual depressive symptoms during CPAP treatment and the pre-CPAP clinical and polysomnographic findings that predicted their improvement.
Section snippets
Patients
The study sample was selected from 20 patients who had been treated for major depressive disorder (MDD) with antidepressants and/or benzodiazepines and were referred to our Sleep Research Center with suspected OSA due to a cluster of symptoms, such as loud snoring, daytime sleepiness, and apnea reported by a witness. They were receiving antidepressants such as selective serotonin reuptake inhibitors (SSRIs), serotonin noradrenaline reuptake inhibitors (SNRIs), or tricyclic antidepressants
Comparison of polysomnographic variables between pre-CPAP and CPAP titration
Table 1 shows a comparison of polysomnographic variables over all nights between pre-CPAP and CPAP titration in MDD patients with OSA (n = 17). CPAP resulted in significant improvements in apnea severity indices of AHI and mean oxygen saturation, sleep maintenance indices of wake time after sleep onset, sleep efficiency and the percentage of stages 1 and 2 sleep. These polysomnographic changes were consistent with the numerous results that have been observed after CPAP treatment in OSA patients,
Discussion
The primary aim of this study was to assess the degree to which CPAP treatment reduces residual depressive symptoms in medicated MDD patients with comorbid OSA. CPAP treatment resulted in a significant improvement of residual depressive symptoms in these patients. BDI and HRSD scores decreased from 19.7 to 10.8 and 16.7 to 8.0 after 2 months of CPAP treatment (both p < 0.01). This result diverges from previous studies demonstrating the positive effect of CPAP treatment on depressive symptoms in
Acknowledgements
This study has no conflicts of interest. This study is indebted to Hiroo Kuwahara, Akina Terayama, Mariko Iwao, and Wakiko Sato for technical assistance.
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