We want to thank Ms Wanting Li for the digital technology support.&#160;This work was supported by&#160;Inner Mongolia Medical Fund (2022QNWN0010, 2023SGGZ047, 2023SGGZ0010).

The study was approved by the Academic Ethics Committee of the Inner Mongolia Mental Health Center (The Third Hospital of Inner Mongolia Autonomous Region, Brain Hospital of Inner Mongolia Autonomous Region) in Hohhot, China. An informed consent form was signed by all study participants.
1. PSG procedure
<ol>
	<li>Data collection
	<ol>
		<li>Include patients with MDD who were diagnosed according to the DSM-V. 
		NOTE: This study included 22 patients with MDD who were di...

Assessing Sleep Quality and Cognitive Function in Patients with Major Depressive Disorder

<ol>
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This two-part protocol has critical steps that demand attention. For PSG, scoring is the most important step; thus, PSG technicians need to be certified and experienced. In addition, before PSG, communication between technicians and participants is necessary because patients might feel uncomfortable and quit during PSG. For the cognitive screening tool, the critical step is evaluating the cognitive function with digitized equipment. Doctors need to introduce the procedures step by step to ensure the participant understan...

Major depressive disorder (MDD), a serious mood disorder that causes significant morbidity and mortality, affects over 300 million people worldwide1. MDD is characterized by low mood, reduced drive, loss of interest, and thoughts of self-harm or suicide2. Cognitive symptoms and sleep disturbance (SD) are two non-mood-related symptoms of MDD3,4. Previous studies have shown that the prevalence of SD is 60-90% in patients with MDD, while the prevalence of sleep disorders among these patients in the Chinese population is 85.22%5. 
Although few studies have investigated the causal relationship between cognitive symptoms and SD, preliminary evidence suggests a significant association between sleep disorders and cognitive symptoms in individuals with MDD6. For example, Cha et al.3 found that subjective sleep quality predicted both subjective cognitive performance and objective cognitive impairments, which were partially mediated by depression severity. Biddle et al.7 also found that among older men with MDD, poor sleep efficiency (SE), measured by actigraphy, was associated with worse cognitive function independent of depression severity. The observed discrepancies may be caused by methodological differences. 
Within this literature, researchers have used various tools to evaluate sleep and cognition. The Pittsburgh Sleep Quality Index (PSQI) was commonly selected as a subjective tool. Actigraphic devices have also been used. However, PSG, regarded as the gold standard for detecting sleep disorders8, is a sensitive, objective SD assessment9. To our knowledge, among the studies of the relationship between sleep and cognition in patients with MDD, few have used PSG to evaluate sleep quality.
Cognitive symptoms in MDD might be multidimensional and addressed in some cases by new pharmacological strategies10,11. Several cognitive assessment tools suitable for MDD have emerged in recent years12. THINC-integrated tool (THINC-it; henceforth referred to as the cognitive screening tool), a validated cognitive screening tool developed by Hou et al.13, is composed of a subjective questionnaire (perceived deficits questionnaire, PDQ-5) and four objective cognitive tests (choice reaction time, 1-back, digit symbol substitution, and trail making part-B). It is considered a time-efficient, acceptable method for detecting cognitive deficits in patients with MDD14. There are two other tools commonly used to assess cognitive function in patients with MDD: the Screen for Cognitive Impairments in Psychiatry-D (SCIP-D) and Cognitive Complaints in Bipolar Disorder Rating Assessment (COBRA)12. The former is an objective tool lacking self-instructed testing, and the latter is a subjective tool lacking an objective version. The constituent tests also differ between these tools. The SCIP-D is comprised of five objective tests: verbal learning, working memory, verbal fluency, delayed memory, and processing speed. The COBRA includes executive function, processing speed and attention, verbal learning and memory, and visual memory12. The recently developed Chinese version of the cognitive screening tool has been confirmed to be a good tool for evaluating cognitive deficits in Chinese patients with MDD15. Thus, using the cognitive screening tool software and PSG, the current study tried to reveal the relationship between cognitive symptoms and SD in MDD patients.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Computer</td>
			<td>Surface</td>
			<td>Surface pro2</td>
			<td></td>
		</tr>
		<tr>
			<td>Derivation</td>
			<td>Compumedics</td>
			<td>Grael</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode</td>
			<td>Compumedics</td>
			<td>Grael</td>
			<td></td>
		</tr>
		<tr>
			<td>Polysomnography</td>
			<td>Compumedics</td>
			<td>Grael</td>
			<td></td>
		</tr>
		<tr>
			<td>Software</td>
			<td>Compumedics</td>
			<td>Compumedics Profusion PSG4</td>
			<td></td>
		</tr>
	</tbody>
</table>

association between sleep quality and cognitive symptoms in patients with major depressive disorder

Cognitive symptoms and sleep disturbance (SD) are common non-mood-related symptoms of major depressive disorder (MDD). In clinical practice, both cognitive symptoms and SD are related to MDD progression. However, there are only a few studies investigating the connection between cognitive symptoms and SD in patients with MDD, and only preliminary evidence suggests a significant association between cognitive symptoms and SD in patients with mood disorders. This study investigates the relationship between cognitive symptoms and sleep quality in patients with major depressive disorder. Patients (n = 20) with MDD were enrolled; their mean Hamilton Depression Scale-17 score was 21.95 (&plusmn;2.76). Gold standard polysomnography (PSG) was used to assess sleep quality, and the validated THINC-integrated tool (the cognitive screening tool) was used to evaluate cognitive function in MDD patients. Overall, the results showed significant correlations between the cognitive screening tool's total score and sleep latency, wake-after-sleep onset, and sleep efficiency. These findings indicate that cognitive symptoms are associated with poor sleep quality among patients with MDD.

Author Spotlight: Unveiling the Connection Between Sleep Disorders and Cognitive Symptoms in Depression

Association Between Sleep Quality and Cognitive Symptoms in Patients with Major Depressive Disorder

In this study, gold standard polysomnography was used to assess sleep quality and the validated cognitive screening tool was used to evaluate cognitive function in major depressive disorder patients. Thinking to recently developed Chinese version of the connecting screening tools has been confirmed to be a good tool for evaluation connective defects in Chinese patients with major depressive disorder. The current study reveals the close relationship between cognitive symptoms and sleep disorders in major depressive disorder patients.

The male/female ratio was 11/9 for the participants. For all the individuals, the age reached 35.35 &#177; 6.83 years, educational level was 14.80 &#177; 3.29 years, Hamilton depression scale-17 (HAMD-17) score was 21.95 &#177; 2.76 points, SE was 76.71 &#177; 8.57%. Regarding the cognitive screening tool scores, PDQ-5, SPO, SC, CB, TMT-B, and total scores were 1756.35 &#177; 395.49, 2046.75 &#177; 684.45, 852.15 &#177; 651.81, 845.75 &#177; 641.15, 911.45 &#177; 619.13 and 4140.80 &#177; 1298.14 points, respectively (<s...

Read this Scientific Article Protocol about Author Spotlight: Unveiling the Connection Between Sleep Disorders and Cognitive Symptoms in Depression at JoVE.com

Here, we present a protocol that investigates the relationship between cognitive symptoms and sleep quality in patients with major depressive disorder. The THINC-integrated tool and polysomnography were used to evaluate cognitive symptoms and sleep quality.