Effect of CPAP treatment on residual depressive symptoms in patients with major depression and coexisting sleep apnea: Contribution of daytime sleepiness to residual depressive symptoms

Abstract

Background

Although extensive studies have indicated a relationship between obstructive sleep apnea (OSA) and depressive symptoms, the effect of continuous positive airway pressure (CPAP) treatment on residual depressive symptoms in patients with both major depressive disorder (MDD) and coexisting OSA has not been examined.

Methods

Seventeen patients with continued MDD despite pharmacotherapy such as antidepressants and/or benzodiazepines, who also had comorbid OSA, were required to complete the Beck Depression Inventory (BDI), Hamilton Rating Scale for Depression (HRSD), and Epworth sleepiness scale (ESS) at the commencement of the study and then again after 2 months of CPAP treatment.

Results

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). We also found significant correlations among the improvement rates in BDI, HRSD and ESS scores (R = 0.86 and 0.75, both p < 0.01). The mixed effect model demonstrated a significant ESS effect on BDI and HRSD.

Conclusions

The results suggest that MDD patients with residual depressive symptoms despite pharmacotherapy who also have symptoms of suspected OSA, such as loud snoring, obesity, and daytime sleepiness, should be evaluated for sleep apnea by polysomnography and treated with an appropriate treatment such as CPAP. CPAP treatment may result in a significant improvement of residual depressive symptoms due to the improvement of daytime sleepiness in these patients.

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.