In-Young Yoon

REM sleep behavior disorder in the Korean elderly population: prevalence and clinical characteristics.

STUDY OBJECTIVES To examine the prevalence and clinical characteristics of REM sleep behavior disorder (RBD) and subclinical RBD in the Korean elderly population. DESIGN A community-based Korean Longitudinal Study on Cognitive Aging and Dementia and time-synchronized video-polysomnography (vPSG) in a laboratory. SETTING Sleep laboratory in a university hospital. PARTICIPANTS 348 individuals aged 60 years or older. INTERVENTION N/A. MEASUREMENTS AND RESULTS Among 696 subjects who were invited to participate in a vPSG study, 348 completed the vPSG. RBD was diagnosed when subjects showed REM sleep without atonia (RSWA) in the vPSG, and had history of complex and vigorous behaviors during sleep or abnormal REM sleep behaviors in the vPSG. Subjects with RSWA but no abnormal REM sleep behaviors were diagnosed with subclinical RBD. Seven subjects (5 male, 2 female) had RBD, three of whom (1 male, 2 female) had Parkinson disease. Two subjects reported history of sleep-related injury. The crude prevalence of RBD and idiopathic RBD was 2.01% (95% confidence interval [CI] = 0.54% to 3.49%) and 1.15% (95% CI = 0.03% to 2.27%). An age and sex-adjusted prevalence estimate of RBD and idiopathic RBD in the Korean elderly was 2.01% and 1.34%. Eighteen subjects were diagnosed with subclinical RBD, and the prevalence of subclinical RBD was estimated to be 4.95%. CONCLUSIONS RBD and subclinical RBD are not rare in the elderly in the community with abnormal REM sleep behaviors of RBD being mild to injurious and violent. The clinical significance and long-term progression of subclinical RBD needs to be further explored, given the prevalence and its possible relation to RBD.

The implication of nigrostriatal dopaminergic degeneration in the pathogenesis of REM sleep behavior disorder

Background and purpose:  The pathogenesis of rapid eye movement (REM) sleep behavior disorder (RBD) is not clear despite its frequent association with Parkinson’s disease (PD). We investigated whether the nigrostriatal dopaminergic system is involved in the development of idiopathic RBD.

The association of nocturnal hypoxemia with arterial stiffness and endothelial dysfunction in male patients with obstructive sleep apnea syndrome.

Background: Obstructive sleep apnea syndrome (OSAS) is associated with cardiovascular complications, and atherosclerosis is considered to mediate this association. Arterial stiffness and endothelial dysfunction are widely accepted as early markers of atherosclerosis. Objectives: The purpose of this study was to investigate the influence of sleep apnea on arterial stiffness and endothelial dysfunction. Methods: We enrolled 83 OSAS patients including 39 with mild to moderate degree (apnea hypopnea index, AHI ≧5, AHI <30) and 44 with severe degree sleep apnea (AHI ≧30) and 29 normal control subjects (AHI <5). After finishing polysomnography, carotid-femoral pulse wave velocity (cfPWV) and flow-mediated dilation (FMD) were measured using noninvasive devices. Results: In patients with severe degree of OSAS, cfPWV was significantly higher than mild to moderate degree of OSAS or normal control subjects. Also, the severe OSAS group showed lower FMD than the normal control group (all p < 0.01). The cfPWV was significantly correlated with FMD (r = –0.26, p < 0.01). Age (β = 0.33, p < 0.01) and percentage of time below 90% O2 saturation (β = 0.34, p < 0.01) were the significant variables to determine cfPWV (adjusted R2 = 21%, p < 0.01) in multivariate analysis, and the lowest O2 saturation was a significant determinant for FMD (β = 0.25, adjusted R2 = 6%, p < 0.01). Conclusions: Nocturnal hypoxemia may alter arterial elasticity and endothelial function in OSAS patients, and those impairments could increase the risk of cardiovascular complications.

Prevalence, comorbidities and risk factors of restless legs syndrome in the Korean elderly population - results from the Korean Longitudinal Study on Health and Aging

The aim of this study was to determine the prevalence, neuropsychiatric comorbidities, iron metabolism and potential risk factors of restless legs syndrome (RLS) in the elderly Korean population. As a community‐based epidemiological study, a simple random sample of 1118 was drawn from a roster of 61 730 adult individuals aged 65 years and older and 714 participated. The diagnosis of RLS was established in face‐to‐face interviews using the four minimal diagnostic criteria for RLS recommended by National Institute of Health. Depressive symptoms, nocturnal sleep disturbances, daytime sleepiness and quality of life were evaluated. Laboratory tests of iron metabolism, markers of inflammation, renal and endocrine function, hormones and vitamins were performed. A total of 59 patients (42 women and 17 men) were diagnosed as RLS with a prevalence of 8.3% (95% confidence interval: 6.2–10.3%), with an almost twofold higher prevalence in women (10.2%) than in men (5.7%). Depression was more prevalent among the subjects with RLS than without RLS and poor nocturnal sleep and quality of life were also observed in subjects with RLS. Daytime sleepiness was observed in 32.8% of subjects with RLS. No significant differences were found in iron metabolism or other risk factors between the subjects with and without RLS. The prevalence of RLS in the Korean elderly population was comparable with that in the Caucasian population. RLS had undesirable effects on mood, sleep quality and general wellbeing of elderly individuals.

The effect of Oros methylphenidate on the sleep of children with attention-deficit/hyperactivity disorder

We evaluated the effect of OROS methylphenidate (MPH) on sleep quality and architecture in children with attention-deficit/hyperactivity disorder (ADHD) using both a parental sleep questionnaire and polysomnography. Twenty-four ADHD children who had no comorbid psychiatric or sleep disorders except for oppositional defiant disorder completed the 6-week, prospective, open-label, flexible-dose trial with OROS MPH (Concerta) monotherapy. After OROS MPH administration, the polysomnography data indicated that the percentage of stage 2 sleep was increased (P=0.024) and the Number of Awakenings was decreased (P=0.047). Relative to baseline, Parasomnias of the Childrens Sleep Habits Questionnaire were decreased (P=0.033). Sleep Onset Latency was not changed during the treatment in general, but was increased in six children with subjective sleep difficulties (F1=5.832, P=0.025, ηp2=0.226). Bedtime Resistance and Sleep Onset Delay in Childrens Sleep Habits Questionnaire were also increased during the treatment with OROS MPH only in individuals with sleep complaints (F1=5.001, P=0.036, ηp2=0.185; F1=7.237, P=0.013, ηp2=0.248). These results suggest that OROS MPH in open-label treatment does not seem to impair sleep and may even improve some aspects of sleep.

Prevalence of narcolepsy-cataplexy in Korean adolescents

Background –  Narcolepsy typically begins between adolescence and early adulthood causing severe neuropsychiatric impairments, but few prevalence studies are available on adolescent narcoleptics. In the present study, we investigated the prevalence of narcolepsy‐cataplexy in adolescents.

Determinants of treatment outcome after use of the mandibular advancement device in patients with obstructive sleep apnea.

OBJECTIVE To determine the predictors affecting treatment outcome after application of the mandibular advancement device (MAD). DESIGN Retrospective analysis. SETTING Tertiary care university hospital. PATIENTS A total of 76 patients (68 men and 8 women) who were treated with the MAD for obstructive sleep apnea (OSA) were included from September 2005 through August 2008. All the subjects underwent cephalometry, nocturnal polysomnography, and sleep videofluoroscopy (SVF) before and at least 3 months after receipt of a custom-made MAD. Sleep videofluoroscopy was performed before and after sleep induction and was analyzed during 3 states of awakeness, normoxygenation sleep, and desaturation sleep. Subjects were divided into success and nonsuccess groups depending on treatment outcome. MAIN OUTCOME MEASURES Multiple variables from cephalometry and SVF including the length of the soft palate, retropalatal space, retrolingual space, and mouth opening angle were evaluated during sleep events with or without the MAD between success and nonsuccess group. RESULTS The soft palate was significantly longer in the nonsuccess group than in the success group. The retropalatal and retrolingual airway spaces and mouth opening angle were not different between 2 groups. Application of the MAD increased the retrolingual space and decreased the length of the soft palate and the mouth opening angle significantly in both success and nonsuccess groups. However, retropalatal space was widened only in the success group, which showed that retropalatal space may be important in determining treatment response of the MAD. CONCLUSION The length of the soft palate showed a difference between success and nonsuccess groups, and widening of retropalatal space might be an important factor for successful outcome with MAD application.

Progression of cognitive impairments in idiopathic REM sleep behaviour disorder

Background Idiopathic REM (rapid eye movement) sleep behaviour disorder (iRBD) has been implicated in cognitive impairments, but there is little evidence about progression of cognitive dysfunction in iRBD. Methods A retrospective follow-up study with patients with iRBD was performed. Conversion to neurodegenerative disorders was analysed by Kaplan-Meier survival analysis. Neuropsychological test results at baseline were compared between patients with iRBD and healthy controls. 57 patients with iRBD were successfully followed up for changes of cognitive performance over time (follow-up duration 50.84±25.38 months; range 12–108 months). Factors affecting cognitive decline were evaluated with multiple regression analysis and the subgroup analysis for groups with and without conversion was carried out. Results Among 84 patients with iRBD, conversion occurred in 18 patients and conversion rates were estimated to be 9%, 18% and 35% at 3, 5 and 6 years from diagnosis of iRBD. Individuals with iRBD showed lower z-scores at baseline than controls in Mini-Mental Status Examination, Trail Making Test A, constructional praxis and Executive Clock Drawing Task (CLOX2). Patients with non-converting iRBD showed significant performance decline in memory (p=0.003, Digit span forward) and a worsening tendency of executive functions (p=0.007, frontal assessment battery; p=0.012, Stroop test) at follow-up tests. Cognitive decline was associated with disease duration or follow-up duration, and lower executive function at baseline increased conversion risk (p=0.031). Conclusions Patients with iRBD have cognitive impairments at baseline and progressive cognitive decline over time. Even in idiopathic cases without development of any neurodegenerative disease, degenerative changes in cognition seem to be under way.

Increased striatal dopamine transporter density in moderately severe old restless legs syndrome patients.

Background and purpose:  Dopamine dysregulation in restless legs syndrome (RLS) may be varied by the severity of RLS, which could contribute to the conflicting results from previous functional neuroimaging studies on the central dopaminergic neurotransmission of RLS. The aim of this study was to observe whether reduced striatal dopaminergic neurotransmission is associated with moderate to moderately severe RLS.

The implication of sleep position in the evaluation of surgical outcomes in obstructive sleep apnea

Objective: To investigate the effect of sleep position on surgical outcomes in obstructive sleep apnea (OSA). Study Design: Retrospective review of 69 consecutive patients. Subjects and Methods: Preoperative and postoperative polysomnographic data and Epworth sleepiness scale were obtained. Patients were categorized into success, response, no response, and failure groups according to apnea-hypopnea index (AHI) after uvulopalatopharyngoplasty. Proportions of supine or lateral position and AHI of each position were evaluated. Position-corrected AHI was developed in order to eliminate the effect of sleep position. Results: Preoperative proportion of supine position in the failure group (n = 26) was 41.3 percent, which was the lowest among four groups (P = 0.010), and increased to 60.8 percent postoperatively (P = 0.028). Twenty-two (84.6%) among the failure group had supine position dependency. Regrouped by position-corrected AHI, 15 patients moved into different groups. Postoperative AHI showed positive correlation with increased supine position when BMI was controlled (r = 0.515, P = 0.006). Conclusion: Without appropriate correction based on the change of sleep position, the fluctuation of sleep position in each polysomnography might confound surgical outcomes in OSA patients. Thus, it is a substantial issue how to control or reflect the positional effect on AHI when treatment results are evaluated.