ABSTRACT
OBJECTIVE: The Epworth Sleepiness Scale is a measure used for the diagnosis of sleep disorders including obstructive sleep apnea (OSA) syndrome, insomnia, and narcolepsy. Although a Korean version has been developed (the KESS), Korean lifestyle such as the floor culture and low driving rates has not been considered. We aim to develop and validate a modified KESS (mKESS) that reflects the Korean lifestyle. METHODS: The sample consisted of 795 healthy participants and 323 OSA patients. The mKESS was developed by modifying several questions to concern the floor culture (questions 1, 2, 6, and 7) and low driving rates (question 8). Feasibility of the modification was tested by comparing the KESS and mKESS using paired samples t-test and by examining internal consistency reliability. Then, mKESS scores of the OSA patients and general participants were compared to test its validity. RESULTS: Questions 1, 2, 7, and 8 were significantly different when comparing the performances of the general population on both scales. Especially, the mean scores on question 8 were significantly different in the non-driver group, but not in the driver group. Cronbach's alpha of the mKESS was relatively higher than that of the KESS. Total mKESS scores of the OSA patients were significantly higher than that of the general population. CONCLUSION: The mKESS is more universally applicable for the clinical evaluation of people that live in Korea. Results support that the mKESS can be administered to measure the average daytime sleep propensity of the Korean population as an alternative to the KESS.
ABSTRACT
People called night owls habitually have late bedtimes and late times of arising, sometimes suffering a heritable circadian disturbance called delayed sleep phase syndrome (DSPS). Those with DSPS, those with more severe progressively-late non-24-hour sleep-wake cycles, and those with bipolar disorder may share genetic tendencies for slowed or delayed circadian cycles. We searched for polymorphisms associated with DSPS in a case-control study of DSPS research participants and a separate study of Sleep Center patients undergoing polysomnography. In 45 participants, we resequenced portions of 15 circadian genes to identify unknown polymorphisms that might be associated with DSPS, non-24-hour rhythms, or bipolar comorbidities. We then genotyped single nucleotide polymorphisms (SNPs) in both larger samples, using Illumina Golden Gate assays. Associations of SNPs with the DSPS phenotype and with the morningness-eveningness parametric phenotype were computed for both samples, then combined for meta-analyses. Delayed sleep and "eveningness" were inversely associated with loci in circadian genes NFIL3 (rs2482705) and RORC (rs3828057). A group of haplotypes overlapping BHLHE40 was associated with non-24-hour sleep-wake cycles, and less robustly, with delayed sleep and bipolar disorder (e.g., rs34883305, rs34870629, rs74439275, and rs3750275 were associated with n=37, p=4.58E-09, Bonferroni p=2.95E-06). Bright light and melatonin can palliate circadian disorders, and genetics may clarify the underlying circadian photoperiodic mechanisms. After further replication and identification of the causal polymorphisms, these findings may point to future treatments for DSPS, non-24-hour rhythms, and possibly bipolar disorder or depression.
ABSTRACT
OBJECTIVE: Delayed sleep phase disorder (DSPD) is a condition in which patients often fall asleep some hours after midnight and have difficulty waking up in the morning. Circadian chronotype questionnaires such as Horne-Östberg Morningness-Eveningness Questionnaire (MEQ) and Basic Language Morningness (BALM) scale have been used for screening for DSPD. This study was to evaluate these two chronotype questionnaires for screening of DSPD. METHODS: The study samples were 444 DSPD and 438 controls. Cronbach's alpha coefficient was calculated to evaluate for internal consistency. An exploratory factor analysis was conducted using principal-axis factoring. The diagnostic performance of a test was evaluated using Receiver Operating Characteristic (ROC) curve analysis. A discriminant function analysis was also performed. RESULTS: For internal consistency, Cronbach's alpha of 0.898 for BALM was higher than the 0.837 for MEQ, though both have acceptable internal consistency. BALM has better construct validity than the MEQ because some MEQ items measure different dimensions. However, when we evaluated the efficiency of two questionnaires for DSPD diagnosis by using the ROC curve, the BALM was similar to the MEQ. In a discriminant analysis with the BALM to classify the two groups (DSPD vs. normal), 6 items were identified that resulted in good classification accuracy. Upon examination of the classification procedure, 94.2% of the originally grouped cases were classified correctly. CONCLUSION: These findings suggest that the BALM has better psychometric properties than the MEQ in screening and discriminating DSPS.
ABSTRACT
OBJECTIVE: The aim of this study was to develop a culturally sensitive instrument that addressed how individuals express and experience depression to detect this disorder in Koreans. We also assessed the validity, reliability, and diagnostic utility of this scale (Lee and Rhee Depression Scale; LRDS). METHODS: The sample consisted of 3,697 normal adults selected from 12 administrative districts (Do) and 448 Korean patients diagnosed with depression using the Structured Clinical Interview for DSM-IV Axis I disorders (SCID-I). Reliability was calculated using Cronbach's α. Construct validity, discriminant validity, and concurrent validity were also measured. Receiver-operator-characteristic (ROC) analysis was employed to evaluate diagnostic efficiency. RESULTS: The LRDS was found to be a reliable instrument (Cronbach's α=0.95) consisting of six factors: negative thinking about the future, negative thinking about the self, worry and agitation, depressed mood, somatization, and loss of volition. Comparison of LRDS scores discriminated the group of patients with depression from the normal individuals in the control group. The measure showed good concurrent validity in that scores were significantly and strongly correlated with scores on established scales such as the Beck Depression Inventory (BDI), the Hamilton Depression Rating Scale (HAM-D), and the D scale of the Minnesota Multiphasic Personality Inventory-second edition (MMPI-2). Diagnostic efficiency was 77.7%, and the cut-off scores were 65 for males and 70 for females. CONCLUSION: To our knowledge, this is the first study to develop a depression-screening scale on the basis of Korean patients' complaints about the disorder. As a culturally sensitive tool, the LRDS will be useful in clinical and research settings in Korea.
ABSTRACT
OBJECTIVE: Tyrosine hydroxylase (TH) is the rate-limiting enzyme in dopamine biosynthesis. Because the TH Val81Met polymorphism is located in the amino-terminal regulatory domain of the tetrameric enzyme, it is a candidate marker for susceptibility to dopamine-related traits. We investigated the hypothesis that TH Val81Met polymorphism can influence susceptibility to tardive dyskinesia (TD) in schizophrenia. METHODS: TH Val81Met polymorphism was analyzed by PCR-based methods in 83 schizophrenic patients with TD and 126 schizophrenic patients without TD, matched for antipsychotic drug exposure and other relevant variables. RESULTS: There was no significant association of the genotype and allele frequencies determined by the TH Val81Met polymorphism between TD and non-TD patients. In addition, there was no significant difference in terms of total Abnormal Involuntary Movement Scale scores among the three genotype groups. CONCLUSION: Within the limitations imposed by the size of the clinical sample, these findings suggest that the Val81Met polymorphism of the TH gene does not contribute significantly to the risk for TD.
