The Mediating Effect of Insomnia on the Relationship between Panic Symptoms and Depression in Patients with Panic Disorder

Background@#This study aimed to determine if sleep disturbances may mediate the relationship between panic symptoms and depression in patients with panic disorder (PD). @*Methods@#Electronic medical records were retrospectively reviewed for 110 consecutive patients with diagnosed PD in an outpatient clinic between October 2018 and December 2019. Measurements include the PD Severity Scale, Beck Depression Inventory-II (BDI-II) and Insomnia Severity Index (ISI). Statistical analyses were performed to assess any potential relationship between PD, insomnia and depression. @*Results@#Of the PD patients, 88 (80%) and 89 (80.9%) had comorbid depression (BDI-II ≥ 14) and insomnia (Korean version of the ISI ≥ 8), respectively. In a mediation model using insomnia as the mediating variable, the total effect of panic symptom severity on depression was significant (t = 7.23, P < 0.001). There were significant effects of panic symptoms on insomnia (t = 4.62,P < 0.001) and of insomnia on depression (t = 6.69, P < 0.001). The main effect of panic symptom severity on depression was also significant, after controlling for the effect of insomnia (t = 5.10, P < 0.001), suggesting partial mediation. @*Conclusion@#Both depressive symptoms and insomnia are common in patients with PD and depression was partially mediated by insomnia in these patients. These results suggest that an intervention for insomnia in patients with PD might help prevent the development of depression.

The Mediating Effect of Insomnia on the Relationship between Panic Symptoms and Depression in Patients with Panic Disorder

Background@#This study aimed to determine if sleep disturbances may mediate the relationship between panic symptoms and depression in patients with panic disorder (PD). @*Methods@#Electronic medical records were retrospectively reviewed for 110 consecutive patients with diagnosed PD in an outpatient clinic between October 2018 and December 2019. Measurements include the PD Severity Scale, Beck Depression Inventory-II (BDI-II) and Insomnia Severity Index (ISI). Statistical analyses were performed to assess any potential relationship between PD, insomnia and depression. @*Results@#Of the PD patients, 88 (80%) and 89 (80.9%) had comorbid depression (BDI-II ≥ 14) and insomnia (Korean version of the ISI ≥ 8), respectively. In a mediation model using insomnia as the mediating variable, the total effect of panic symptom severity on depression was significant (t = 7.23, P < 0.001). There were significant effects of panic symptoms on insomnia (t = 4.62,P < 0.001) and of insomnia on depression (t = 6.69, P < 0.001). The main effect of panic symptom severity on depression was also significant, after controlling for the effect of insomnia (t = 5.10, P < 0.001), suggesting partial mediation. @*Conclusion@#Both depressive symptoms and insomnia are common in patients with PD and depression was partially mediated by insomnia in these patients. These results suggest that an intervention for insomnia in patients with PD might help prevent the development of depression.

A Study on the Characteristics and Consultation Request Type of Inpatients Referred for Depressive Symptoms / 정신신체의학

Objectives@#：The purpose of this study is to investigate the characteristics of depressive patients who admitted to general hospital. We examined the clinical characteristics of patients who were referred to the Department of Psychiatry as depressive symptoms, according to the type of consultation request, and comparing ‘with re-consultation’ and ‘without re-consultation’ groups. @*Methods@#：We performed a retrospective chart review of 4,966 inpatients who were referred to the Department of Psychiatry from August 2005 to December 2011. @*Results@#：For about 6 years, among the inpatients referred for psychiatric consultation, a total of 647 patients were referred for depressive symptoms, accounting for 13.82% of the total consultations. The average age of depressive patients was 58.6 years, which was higher than the average of 56.4 years of overall patients. Among the depressive patients, 275 patients were included in ‘with re-consultation’ group and there was no statistically significant difference when comparing ‘with re-consultation’ group and ‘without re-consultation’ group. How-ever, there was a difference in the tendency of the two groups in the type of consultation request. ‘With re-consultation’ group was in the order of frequency of consultation type 3-2-1, whereas the ‘without re-consultation’ group was in the order of frequency of consultation type 2-3-1. @*Conclusions@#：The group of inpatients who were referred for depressive symptoms in general hospital showed the largest proportion of the group of patients referred to the Department of Psychiatry. ‘With re-consultation’ group had a higher rate of re-consultation due to the occurrence of new symptoms after hospitalization compared to ‘without re-consultation’ group. Therefore, doctors in each department and psychiatrists should pay attention to the depressive symptoms of inpatients and actively discuss treatment plans to improve the quality of medical services, identify risk factors, and make efforts to intervene early if necessary.

Frequency of Depressive Disorders According to Cognitive Continuum in the Elderly Living in the Community

Objective@#We investigated the frequency of depressive disorders in the elderly with normal cognition (NC), mild cognitive impairment (MCI) and dementia patients living in the community to find out the association between cognitive disorders and depressive disorders in the community dwelling elderly. @*Methods@#6,262 baseline study subjects from November 2010 through October 2012 were enrolled based on the Korean longitudinal study on cognitive aging and dementia which is the first nationwide multi-center population based prospective cohort study in Korea. Diagnosis of MCI, dementia, major depressive disorder (MDD), minor depressive disorder (mDD) and subsyndromal depression (SSD) was made by psychiatrists with expertise in dementia based on the appropriate diagnostic criteria. @*Results@#4,303 NC, 1,737 MCI, 222 dementia were enrolled. The frequency of MDD, mDD, SSD were highest in dementia and lowest in NC and showed significant difference among three groups. The odds ratio also increased significantly in MCI and dementia compared with NC showing highest odds ratio in dementia. @*Conclusion@#Our findings propose that MCI and dementia in the community dwelling elderly were significantly associated with various types of depressive disorders showing highest association tendency in dementia.

Predictors of Psychiatric Outpatient Adherence after an Emergency Room Visit for a Suicide Attempt

Objective@#This study aimed to investigate the potential correlation between baseline characteristics of individuals visiting an emergency room for a suicide attempt and subsequent psychiatric outpatient treatment adherence. @*Methods@#Medical records of 525 subjects, who visited an emergency room at a university-affiliated hospital for a suicide attempt between January 2017 and December 2018 were retrospectively reviewed. Potential associations between baseline characteristics and psychiatric outpatient visitation were statistically analyzed. @*Results@#107 out of 525 individuals (20.4%) who attempted suicide visited an outpatient clinic after the initial emergency room visit. Several factors (e.g., sober during suicide attempt, college degree, practicing religion, psychiatric treatment history) were significantly related to better psychiatric outpatient follow-up. @*Conclusion@#Several demographic and clinical factors predicted outpatient adherence following a suicide attempt. Therefore, additional attention should be given to suicide attempters who are at the risk of non-adherence by practitioners in the emergency room.

Low Diastolic Blood Pressure and Cognitive Decline in Korean Elderly People: The Korean Longitudinal Study on Cognitive Aging and Dementia

Objective@#Cardiovascular diseases are representative risk factors for the onset of cognitive decline. The purpose of this study was to confirm the relationship between diastolic blood pressure and cognitive function in elderly people in Korea. @*Methods@#Data from subjects who were enrolled in the prospective Korean Longitudinal Study on Cognitive Aging and Dementia were used in this study. Data from 701 subjects whose diastolic blood pressure range did not change (≤79 mm Hg or ≥80 mm Hg) over 2 years were analyzed. To analyze the differences in cognitive function between the groups at the 2-year follow-up, an analysis of covariance was performed with covariates, which were significantly different between the two groups, and the baseline cognitive function. @*Results@#Significant differences were observed between the two groups, and the mean scores on the constructional praxis (η2=0.010) and word list recall tests (η2=0.018) in the diastolic blood pressure ≥80 mm Hg group were higher than those in the diastolic blood pressure ≤79 mm Hg group at the 2-year follow-up. @*Conclusion@#These results indicate that maintaining a DBP below 79 mm Hg presents a greater risk of cognitive decline in Korean elderly people.

Driving-Related Adverse Events in the Elderly Men: A Population-Based Prospective Cohort Study

Objective@#This study estimated the incidence of driving-related adverse events and examined the association of cognitive function with the risk of future driving-related adverse events in the elderly Korean male population. @*Methods@#We analyzed 1,172 male drivers aged 60 years or older in the Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD). Using the data from Korean National Police Agency, we classified the participants into three groups: safe driving (drove for 2 years after baseline without a traffic accident or repeated violations), driving cessation (stopped driving), and risky driving (one or more traffic accidents or repeated violations). We estimated the incidences of driving cessation and risky driving, and examined the effect of cognitive function on their risks. @*Results@#The incidence of driving cessation and risky driving in the Korean male drivers aged 60 years or older was 19.3 and 69.9 per 1,000 person-years respectively and increased in the late 80s. Drivers with better baseline Word List Memory Test scores showed less risky driving (OR=0.94, p=0.039). @*Conclusion@#Driving-related adverse events increased in late 80s, and better memory function was protective against these events.

Development of a Screening Algorithm for Alzheimer's Disease Using Categorical Fluency and Confrontational Naming Abilities

OBJECTIVE: Declines in naming ability and semantic memory are well-known features of early Alzheimer's disease (AD). We developed a new screening algorithm for AD using two brief language tests : the Categorical Fluency Test (CFT) and 15-item Boston Naming Test (BNT15). METHODS: We administered the CFT, BNT15, and Mini-Mental State Examination (MMSE) to 150 AD patients with a Clinical Dementia Rating of 0.5 or 1 and to their age- and gender-matched cognitively normal controls. We developed a composite score for screening AD (LANGuage Composite score, LANG-C) that comprised demographic characteristics, BNT15 subindices, and CFT subindices. We compared the diagnostic accuracies of the LANG-C and MMSE using receiver operating curve analysis. RESULTS: The LANG-C was calculated using the logit of test scores weighted by their coefficients from forward stepwise logistic regression models : logit (case)=12.608−0.107×age+1.111×gender+0.089×education−0.314×HS(1st)−0.362×HS(2nd)+0.455×perseveration+1.329×HFCR(2nd)−0.489×MFCR(1st)−0.565×LFCR(3rd). The area under the curve of the LANG-C for diagnosing AD was good (0.894, 95% confidence interval=0.853–0.926 ; sensitivity=0.787, specificity=0.840), although it was smaller than that of the MMSE. CONCLUSION: The LANG-C, which is easy to automate using PC or smart devices and to deliver widely via internet, can be a good alternative for screening AD to MMSE.

Anhedonia and Dysphoria Are Differentially Associated with the Risk of Dementia in the Cognitively Normal Elderly Individuals: A Prospective Cohort Study

OBJECTIVE: We investigated the impact of depressed mood (dysphoria) and loss of interest or pleasure (anhedonia)on the risk of dementia in cognitively-normal elderly individuals. METHODS: This study included 2,685 cognitively-normal elderly individuals who completed the baseline and 4-year follow-up assessments of the Korean Longitudinal Study on Cognitive Aging and Dementia. We ascertained the presence of dysphoria and anhedonia using the Mini International Neuropsychiatric Inventory. We defined subjective cognitive decline as the presence of subjective cognitive complaints without objective cognitive impairments. We analyzed the association of dysphoria and anhedonia with the risk of cognitive disorders using multinomial logistic regression analysis adjusted for age, sex, education, Cumulative Illness Rating Scale score, Apolipoprotein E genotype, and neuropsychological test performance. RESULTS: During the 4-year follow-up period, anhedonia was associated with an approximately twofold higher risk of mild cognitive impairment (OR=2.09, 95% CI=1.20–3.64, p=0.008) and fivefold higher risk of dementia (OR=5.07, 95% CI=1.44–17.92, p=0.012) but was not associated with the risk of subjective cognitive decline. In contrast, dysphoria was associated with an approximately twofold higher risk of subjective cognitive decline (OR=2.06, 95% CI=1.33–3.19, p=0.001) and 1.7-fold higher risk of mild cognitive impairment (OR=1.75, 95% CI=1.00–3.05, p=0.048) but was not associated with the risk of dementia. CONCLUSION: Anhedonia, but not dysphoria, is a risk factor of dementia in cognitively-normal elderly individuals.

Mature Defense Mechanisms Affect Successful Adjustment in Young Adulthood-Adjustment to Military Service in South Korea

OBJECTIVE: A defense mechanism is an automatic psychological process necessary for successful adaptation. It reflects adaptive capacity. The purpose of this study is to explore the relationship between the adaptation ability of individuals who face mandatory military service and the pattern of defense mechanisms. METHODS: The subjects were 69 men (21.4±2.2 years) who expressed psychological difficulties in three military service situations. Control group was 36 men (24.0±1.4 years) who had successfully completed military service. We examined psychiatric history, the pattern of defense mechanisms, and depression and anxiety levels. Defense mechanisms were compared between two groups. RESULTS: The maladjusted group used immature defenses more frequently than the control group did. There were no differences in the defense patterns according to diagnosis. The control group used more identification and rationalization, classified as immature defenses. The temporarily maladjusted group used more somatization, regression, and avoidance. CONCLUSION: Using mature defense mechanisms helped young adults to adapt to a particular situation. The maturity of the defense is more valuable than the psychiatric diagnosis. Some immature defenses are also helpful to adapt. We cautiously assume that some defenses can be protective or risk factors in adapting to stressful situations by young adults.

Normal-But-Low Serum Folate Levels and the Risks for Cognitive Impairment

OBJECTIVE: This study aimed to examine the association between normal-but-low folate levels and cognitive function in the elderly population using a prospective cohort study. METHODS: We analyzed 3,910 participants whose serum folate levels were within the normal reference range (1.5–16.9 ng/mL) at baseline evaluation in the population-based prospective cohort study named the “Korean Longitudinal Study on Cognitive Aging and Dementia.” The association between baseline folate quartile categories and baseline cognitive disorders [mild cognitive impairment (MCI) or dementia] was examined using binary logistic regression analysis adjusting for confounding variables. The risks of incident MCI and dementia associated with the decline of serum folate level during a 4-year follow-up period were examined using multinomial logistic regression analysis. RESULTS: The lowest quartile group of serum folate (≥1.5, ≤5.9 ng/mL) showed a higher risk of cognitive disorders than did the highest quartile group at baseline evaluation (odds ratio 1.314, p=0.012). Over the 4 years of follow-up, the risk of incident dementia was 2.364 times higher among subjects whose serum folate levels declined from the 2nd–4th quartile group to the 1st quartile than among those for whom it did not (p=0.031). CONCLUSION: Normal-but-low serum folate levels were associated with the risk of cognitive disorders in the elderly population, and a decline to normal-but-low serum folate levels was associated with incident dementia. Maintaining serum folate concentration above 5.9 ng/mL may be beneficial for cognitive status.

Analysis of State-Trait Anxiety Inventory for Patients Diagnosed with Insomnia in an Outpatient Department / 수면정신생리

OBJECTIVES@#Insomnia patients who visited the psychiatric outpatient of a university department, were divided into those patients with insomnia alone and those with depression or anxiety disorder, along with insomnia. The study analyzed their demographic characteristics and the differences in State-Trait Anxiety Inventory (STAI) results among the patient groups.@*METHODS@#Patients who visited the psychiatric department in Konkuk University hospital from 1 January 2006 to 31 December 2018. If they were diagnosed with insomnia disorder based on DSM IV-TR and had undergone STAI, their electronic records were retrospectively analyzed. Based on the records, the patients were classified into those with insomnia disorder only, those with insomnia and anxiety disorder, and those with insomnia and depressive disorder. This study analyzed the demographic characteristics and STAI results of each group, and compared the differences among those groups.@*RESULTS@#During the period, 99 of 329 insomnia disorder patients who had performed STAI were diagnosed with depressive concurrent disorder and 61 with concurrent anxiety disorder. There was no difference in demographic characteristics of age and sex ratio among the three patient groups, and all had greater than 70% proportions of patients aged from 50s to 70s (71.8%, 77.1%, and 73.8% respectively). The average scores of STAI-I were 51.85 ± 10.15 for the patients with anxiety disorders and 54.18 ± 10.32 for those with depressive disorders, both of which were higher than the score of the patients with insomnia alone (44.55 ± 8.89). However, the score difference was not statically significant between the anxiety and depression groups. Similarly, in the STAI-II comparison, the averages of patients with anxiety or depressive disorders along with insomnia were 49.98 ± 8.31 and 53.19 ± 10.13 respectively, which were higher than that of the insomnia only group (42.71 ± 8.84), but there was no significant difference between the anxiety and depressive disorder groups.@*CONCLUSION@#Although there were no differences in demographic data between the patients with insomnia only and those with accompanying depressive or anxiety disorder, the STAI-I and II scores were lower in the insomnia only group. In the future, it is necessary to consider other demographic characteristics including comorbidities and to conduct similar analyses with a larger sample.

Overview of the Korean Longitudinal Study on Cognitive Aging and Dementia

OBJECTIVE: Due to an unprecedented rate of population aging, South Korea is facing a dementia epidemic. For this reason, the Korean Longitudinal Study on Cognitive Aging and Dementia (KLOSCAD) was launched in 2009 with support from the Korean Health Industry Development Institute to investigate the epidemiology, biopsychosocial risk factors, and outcomes of dementia and dementia-related conditions. METHODS: The KLOSCAD is the first nationwide multi-center population-based prospective cohort study. In October 2010, 12,694 individuals were randomly sampled from residents aged 60 years or older who lived in 13 districts across South Korea. In the baseline assessment, which was conducted from November 2010 through October 2012, 6,818 (53.7%) individuals participated. Follow-up assessments have been conducted every two years, with the first follow-up assessment conducted between November 2012 and October 2014, and the second between November 2014 and October 2016. The third is now in progress, and will span from November 2016 to October 2018. Diagnosis of cognitive disorders, neuropsychological battery, behavioral and psychological symptoms of dementia, activities of daily living, physical and neurologic examination and laboratory tests, life styles, quality of life, and identification of death were evaluated in each assessment. RESULTS: The cumulative drop-out rate at the second follow-up assessment was 38.7%. Dementia and mild cognitive impairment were 5.0% and 27.0%, respectively. CONCLUSION: The KLOSCAD may provide strong scientific evidence for advancing the fight against dementia both in Korea and globally.

Prevalence and Risk Factors of Abusive Behaviors in the Caregivers of People with Dementia in Korea

OBJECTIVE: We investigated the prevalence and risk factors of physically abusive behaviors (PhAB) and psychologically abusive behaviors (PsAB) towards people with dementia (PWD) in family caregivers, and compared their prevalences between East Asian and Western countries. METHODS: We estimated the prevalence and risk factors of PhAB and PsAB in 467 Korean pairs of community-dwelling PWD and their primary family caregivers. We evaluated abusive behaviors using the Modified Conflict Tactics Scale. In addition, we compared the prevalence of abusive behaviors between Asian and Western countries through a meta-analysis on 12 studies including the current one. RESULTS: More than a half of the caregivers reported PsAB and about one out of seven caregivers admitted PhAB within past three months. PsAB and PhAB were slightly more prevalent in East Asian countries than in Western countries. Non-Alzheimer type and moderate to severe behavioral and psychological symptoms of dementia were associated with the risk of PhAB but not with the risk of PsAB. Severe care burden and low income were associated with the risk of PhAB and PsAB. CONCLUSION: PhAB and PsAB were as prevalent in the family caregivers of PWD in Asian countries including Korea as in Western countries. Prevention strategies should be implemented according to the type of abusive behaviors.

Reversed Hand Movement during Sleep in Patients with Obstructive Sleep Apnea

OBJECTIVE: Previous findings suggest that hand movement laterality is reversed during sleep. The present study aimed to verify this phenomenon and evaluate whether the extent of reversal is correlated with the severity of sleep apnea. METHODS: A total of 184 participants (mean age: 44.5±13.0 years; 81.5% males) wore actigraphs on both hands during sleep, and nocturnal polysomnography was simultaneously performed. RESULTS: Actigraphic indices of hand movement were significantly higher for the left hand than those for the right hand (p < 0.001), including total activity score, mean activity score, mean score in active periods and fragmentation index. Additionally, calculated differences between the fragmentation index for the left versus right hands were significantly correlated with the apnea-hypopnea index (AHI, r=0.149, p=0.032). The AHI was not significantly correlated with differences in hand movement between both hands movement assessed by total activity score (r=0.004, p=0.957), mean activity score (r=0.011, p=0.876), mean score in active periods (r=-0.080, p=0.255). CONCLUSION: More severe symptoms of obstructive sleep apnea was associated with larger degree of hand movement reversal at night. This result support the theory that homeostatic deactivation occurs in the dominant hemisphere during sleep.

The Characteristics and Types of Psychiatric Consultation for Insomnia Symptom in Hospitalized Patients / 수면정신생리

OBJECTIVES: The purpose of this study was to explore insomniac demographic characteristics and the type of consultation provided to hospitalized patients asked to the Department of Psychiatry for insomnia and to compare patient insomnia characteristics by consultation type. METHODS: We performed a retrospective chart review of 4,966 patients who were hospitalized from August 1, 2005 to December 31, 2011 that received consultation in the Department of Psychiatry. Among them, 236 patients were referred for insomnia. We compared the differences in demographic characteristics and types of consultation between the insomnia patient group and other patient group. We also compared the difference between demographic characteristics and type of consultation by dividing total subjects into ‘with reconsultation’ and ‘without reconsultation’ groups. RESULTS: Our results came from the analysis of 9,689 consecutive consultation requests. There were 4,966 patients that participated in the study over 6 years and 6 months. The overall consultation rate was 3.3% of all admissions and insomnia patients comprised 4.8% of those. The ratio of re-consultation for insomnia was 27.5%. There was no significant difference in mean age between the insomnia ‘with reconsultation group’ and the insomnia ‘without reconsultation group’, but the ‘with reconsultation’ group had significantly more male patients and medical patients than the ‘without re-consultation’ group. For insomnia patients, consultation types were in the order of Mending request (51.3%), Paralle request (36.6%), Complementary request (9.0%) and this composition differed from that of total admission patients. CONCLUSION: Hospitalized patients referred for insomnia showed a higher proportion of male patients, lower rates of re-consultation compared with other patients, and most of these were for secondary insomnia. Each doctor should be aware of the possibility of inpatient insomnia, conduct positive assessments and referrals as necessary, and psychiatrists who might be asked for consultation need to prepare an active intervention with initial diagnosis and treatment, as well as recommendations for the timing of reconsultation.

Change of Heart Rate Variability in Depressive Disorder after Physical or Psychological Stress / 수면정신생리

OBJECTIVES: This study was designed to assess the change of heart rate variability (HRV) at resting, upright, and psychological stress states in depressive disorder patients. METHODS: HRV was measured at resting, upright, and psychological stress states in 62 depressive disorder patients. We used visual analogue scale (VAS) score to assess tension and stress severity. Beck depression inventory (BDI) and state trait anxiety inventories I and II (STAI-I and II) were used to assess depression and anxiety severity, respectively. Differences between HRV indices and VAS score were evaluated using paired t-tests. Gender difference analysis was conducted with ANCOVA. RESULTS: SDNN (standard deviation of normal to normal intervals), LF/HF (low frequency/high frequency), and VLF (very low frequency) were significantly increased, while NN50 and pNN50 were significantly decreased in the upright position compared to resting state. SDNN, RMSSD (root mean square of the differences of successive normal to normal intervals), and VLF were significantly increased, while pNN50 was significantly decreased in the psychological stress state compared to resting state. SDNN, NN50, and pNN50 were significantly lower in an upright position compared to a state of psychological stress, and LF, HF, and LF/HF showed no significant differences CONCLUSION: The LF/HF ratio was significantly increased after physical stress in depressive disorder. However, the LF/HF ratio was not significantly increased after psychological stress, and the change in LF/HF ratio after physical stress and psychological stress did not significantly differ from each other. Significant increase in SDNN, NN50, and pNN50 in an upright posture compared to psychological stress suggests that depressive patients react more sensitively to physical stress than psychological stress.

Reversible Delayed Hypoxic Leukoencephalopathy from Respiration Failure during Sleep

No abstract available.

The Clinical Significance of Cognitive Interventions for the Patients with Mild Cognitive Impairment / 신경정신의학

Patients with mild cognitive impairment (MCI) are at increased risk of developing dementia and Alzheimer's disease (AD). Currently, no disease-modifying or preventive drugs for AD are available. Non-pharmacological interventions, including cognitive intervention and physical exercise, could assist in the prevention and treatment of AD. Cognitive interventions can improve cognition and prevent dementia, and promote cognitive reserve and plasticity. As there are few standardized intervention programs for the treatment of MCI, development and effective study of cognitive interventions are needed. Psychiatrists should have a great interest in this kind of non-pharmacological interventions regarding neurocognitive disorders.

Correlational Analysis of Supine Position Time and Sleep-related Variables in Obstructive Sleep Apnea Syndrome / 수면정신생리

OBJECTIVES: A supine sleep position increases sleep apneas compared to non-supine positions in obstructive sleep apnea syndrome (OSAS). However, supine position time (SPT) is not highly associated with apnea-hypopnea index (AHI) in OSAS. We evaluated the correlation among sleep-related variables and SPT in OSAS. METHODS: A total of 365 men with OSAS were enrolled in this study. We analyzed how SPT was correlated with demographic data, sleep structure-related variables, OSAS-related variables and heart rate variability (HRV). Multiple linear regression analysis was conducted to investigate the factors that affected SPT. RESULTS: SPT had the most significant correlation with total sleep time (TST ; r = 0.443, p < 0.001), followed by sleep efficiency (SE ; r = 0.300, p < 0.001). Snoring time (r = 0.238, p < 0.001), time at < 90% SpO2 (r = 0.188, p < 0.001), apnea-hypopnea index (AHI ; r = 0.180, p = 0.001) and oxygen desaturation index (ODI ; r = 0.149, p = 0.004) were significantly correlated with SPT. Multiple regression analysis revealed that TST (t = 7.781, p < 0.001), snoring time (t = 3.794, p < 0.001), AHI (t = 3.768, p < 0.001) and NN50 count (t = 1.993, p = 0.047) were associated with SPT. CONCLUSION: SPT was more highly associated with sleep structure-related parameters than OSAS-related variables. SPT was correlated with TST, SE, AHI, snoring time and NN50 count. This suggests that SPT is likely to be determined by sleep structure, HRV and the severity of OSAS.