Abnormalities of Rest-Activity and Light Exposure Rhythms Associated with Cognitive Function in Patients with Mild Cognitive Impairment (MCI).

We aimed to examine the difference in rest-activity rhythm (RAR) and light exposure rhythm (LER) between patients with mild cognitive impairment (MCI) and normal controls (NC), and to verify their relationships with cognitive functions. The neuropsychological battery was administered to participants above 50 years old. The MCI diagnosis was made according to Petersen's criteria. Ten patients with MCI (77.90 ± 6.95 years) and eight NC (74.75 ± 5.06 years) were studied. Actigraphy (Actiwatch 2; Philips Respironics) was recorded at home for 5 days. RAR and LER variables, including interdaily stability (IS), intradaily variability (IV) and relative amplitude, were calculated using nonparametric analyses. The associations between cognitive performance and RAR and LER variables were explored using generalized linear models. There were no significant differences in RAR or LER variables between MCI and NC. There was a significant main effect of RAR-IS on the Stroop Color and Word Test (SCWT), indicating a positive relationship between RAR stability and SCWT performance. There was a significant group by RAR-IS interaction on Trail Making Test-A, indicating a negative relationship in MCI compared to NC. There was a significant group by LER-IV interaction on the Boston Naming Test, indicating a positive relationship in MCI compared to NC. There was no disruption in RAR and LER in patients with MCI. Our study showed that circadian rhythm abnormality was associated with a decline in executive function. However, circadian rhythm abnormality was not associated with declines in processing speed and language function in patients with MCI, implying an altered pathophysiology compared to NC.

A normative study of total scores of the CERAD neuropsychological assessment battery in an educationally diverse elderly population.

BACKGROUND: This study aimed to investigate the influences of age, education, and gender on the two total scores (TS-I and TS-II) of the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological assessment battery (CERAD-NP) and to provide normative information based on an analysis for a large number of elderly persons with a wide range of educational levels. METHODS: In the study, 1,987 community-dwelling healthy volunteers (620 males and 1,367 females; 50-90 years of age; and zero to 25 years of education) were included. People with serious neurological, medical, and psychiatric disorders (including dementia) were excluded. All participants underwent the CERAD-NP assessment. TS-I was generated by summing raw scores from the CERAD-NP subtests, excluding Mini-Mental State Examination and Constructional Praxis (CP) recall subtests. TS-II was calculated by adding CP recall score to TS-I. RESULTS: Both TS-I and TS-II were significantly influenced by demographic variables. Education accounted for the greatest proportion of score variance. Interaction effect between age and gender was found. Based on the results obtained, normative data of the CERAD-NP total scores were stratified by age (six overlapping tables), education (four strata), and gender. CONCLUSIONS: The normative information will be very useful for better interpretation of the CERAD-NP total scores in various clinical and research settings and for comparing individuals' performance of the battery across countries.

Circadian Rhythm Sleep Disorders.

OBJECTIVE: To review circadian rhythm sleep disorders, including underlying causes, diagnostic considerations, and typical treatments. METHODS: Literature review and discussion of specific cases. RESULTS: Survey studies 1,2 suggest that up to 3% of the adult population suffers from a circadian rhythm sleep disorder (CRSD). However, these sleep disorders are often confused with insomnia, and an estimated 10% of adult and 16% of adolescent sleep disorders patients may have a CRSD 3-6. While some CRSD (such as jet lag) can be self-limiting, others when untreated can lead to adverse medical, psychological, and social consequences. The International Classification of Sleep Disorders classifies CRSD as dyssomnias, with six subtypes: Advanced Sleep Phase Type, Delayed Sleep Phase Type, Irregular Sleep Wake Type, Free Running Type, Jet Lag Type, and Shift Work Type. The primary clinical characteristic of all CRSD is an inability to fall asleep and wake at the desired time. It is believed that CRSD arise from a problem with the internal biological clock (circadian timing system) and/or misalignment between the circadian timing system and the external 24-hour environment. This misalignment can be the result of biological and/or behavioral factors. CRSD can be confused with other sleep or medical disorders. CONCLUSIONS: Circadian rhythm sleep disorders are a distinct class of sleep disorders characterized by a mismatch between the desired timing of sleep and the ability to fall asleep and remain asleep. If untreated, CRSD can lead to insomnia and excessive daytime sleepiness, with negative medical, psychological, and social consequences. It is important for physicians to recognize potential circadian rhythm sleep disorders so that appropriate diagnosis, treatment, and referral can be made.

The Timing of the Melatonin Onset and Phase Angle to Sleep Onset in Older Adults after Uncontrolled vs. Controlled Lighting Conditions.

The main aim of this study was to explore how melatonin onset timing and phase angle to bedtime in healthy older adults are impacted by prior light exposure. A total of 13 healthy older (ages 56-74) individuals were studied on two successive evenings. Prior to the first evening, the participants were in self-selected lighting conditions for the first 4-6 h of the day and then were in dim light (3 lux) until their scheduled bedtime. On the second day, individuals from Project A remained in the dim lighting conditions throughout the entire day but those in Project B were in more typical indoor lighting (~90 lux) throughout the day. On both evenings, hourly blood samples were collected and assayed for melatonin, and melatonin onset timing and phase angle to sleep onset was determined. Overall, melatonin onset was earlier and the phase angle was larger on Night 1 than on Night 2. In Project A there was no significant difference between melatonin onset on night 1 vs. night 2. However, in Project B melatonin onset was significantly later on Night 2 (in typical indoor lighting) than on Night 1 (in dim lighting). Our results suggest that in older people, uncontrolled bright light early in the day did not impact the timing of dim light melatonin onset (DLMO) when assessed later that same evening. However, in older adults, exposure to ordinary room light during melatonin phase assessment appeared to suppress melatonin, leading to a later observed time of melatonin onset, as has been reported previously for young adults.

Effect of Personalized Blue-Enriched White Light Intervention on Rest-Activity and Light Exposure Rhythms in Mild and Moderate Alzheimer's Disease.

OBJECTIVE: We aimed to examine the effectiveness of personalized light intervention using a blue-enriched light-emitting-diodes device on rest-activity rhythm (RAR) and light exposure rhythm (LER) in patients with mild and moderate Alzheimer's disease (AD). METHODS: AD patients with poor sleep quality and/or insomnia symptoms were assigned into either an experimental group (EG) or control group (CG) in a single-blind design. Personalized light intervention was given at 9-10 h after individual dim light melatonin onset, lasting for 1 h every day for two weeks in the EG (77.36±5.79 years, n=14) and CG (78.10±7.98 years, n=10). Each patient of CG wore blue-attenuating sunglasses during the intervention. Actigraphy recording at home for 5 days was done at baseline (T0), immediate postintervention (T1), and at four weeks after intervention (T2). The variables of RAR and LER were derived using nonparametric analysis. RESULTS: We found a significant time effect on the intradaily variability (IV) of RAR at T2 with respect to T0 (p=0.039), indicating reduced IV of RAR at four weeks after personalized light intervention regardless of blue-enriched light intervention. There was a time effect on the IV of LER at T1 with respect to T0 (p=0.052), indicating a reduced tendency in the IV of LER immediately after intervention. CONCLUSION: Our personalized light intervention, regardless of blue-enriched light source, could be useful in alleviating fragmentation of RAR and LER in AD patients.

Neurocognitive dysfunction associated with sleep quality and sleep apnea in patients with mild cognitive impairment.

OBJECTIVES: Sleep apnea syndrome (SAS) is considered a risk factor for cognitive decline in the elderly. The specific neurocognitive decline has been suggested as a predictive factor for dementia in patients with mild cognitive impairment (MCI). The authors aim to illustrate the sleep characteristics related to the specific neurocognitive decline in the community-dwelling elderly including patients with MCI. DESIGN: Cross-sectional. SETTINGS: Center for sleep and chronobiology in Kangwon National University Hospital. PARTICIPANTS: Thirty patients with MCI and 30 age- and sex-matched normal elderly subjects were selected. MEASUREMENTS: The authors administered seven tests in the Korean version of the Consortium to Establish A Registry of Alzheimer's Disease Neuropsychological battery and conducted nocturnal polysomnography. A p value below 0.05 was considered a statistical significance. RESULTS: There was no significant difference in sleep parameters between the MCI and normal comparison (NC) groups. Sleep efficiency was positively correlated with Constructional Recall (CR) scores in both NC and MCI groups (r = 0.393 and 0.391, respectively). The amount of slow wave sleep (SWS) was also positively correlated with Boston naming test (BNT) scores in both groups (r = 0.392, 0.470, respectively). Stepwise multiple regression models showed that SWS and the apnea index were significant independent variables associated with the BNT score (Δß = 0.43 and -0.34, respectively; adjusted R = 0.298) in the MCI group, and the amount of rapid eye movement sleep was a significant independent variable associated with the CR score (Δß = 0.49; adjusted R = 0.217) in the NC group. CONCLUSIONS: Our results show that poor sleep quality and greater severity of SAS were associated with impaired language function reflecting frontal-subcortical pathology in patients with MCI. This suggests that vulnerability to a specific brain damage associated with SAS could increase the risk for dementia.

Positive effect of timed blue-enriched white light on sleep and cognition in patients with mild and moderate Alzheimer's disease.

Conflicting results have been reported regarding the effectiveness of light treatment (LT) in patients with Alzheimer's disease (AD). We investigated the effectiveness of blue-enriched white LT on sleep, cognition, mood and behavior in patients with mild and moderate AD. The treatment group (n = 14) sat about 60 cm away from a small (136 × 73 × 16 mm) LED light box for 1 h each morning for 2 weeks. The control group (n = 11) wore dark, blue-attenuating sunglasses during the 1 h exposures. The morning light started 9-10 h after each individual's dim light melatonin onset (DLMO). Assessments were done at baseline (T0), immediate post-treatment (T1), and 4 weeks after the end of the 2 weeks of LT (T2). Sleep was measured by actigraphy. Blue-enriched LT had a significantly better effect on the Pittsburgh Sleep Quality Index at T2 compared to blue-attenuated LT, and a trend of better effectiveness on total sleep time at T2. There was a significant increase in Mini-Mental State Examination score at T2 after blue-enriched LT than that at T0. Our findings suggest that morning blue-enriched LT has a benefit in improving sleep and cognitive function in AD patients.

Total scores of the CERAD neuropsychological assessment battery: validation for mild cognitive impairment and dementia patients with diverse etiologies.

OBJECTIVES: This study aimed to validate the two total scores (TS-I and TS-II) of the Consortium to Establish a Registry for Alzheimer Disease neuropsychological battery (CERAD-NP) for a large elderly population including mild cognitive impairment (MCI) and dementia patients with various etiologic backgrounds. The authors also investigated whether the addition of frontal-executive function score can improve the discrimination accuracy of the total scores for dementia and MCI. DESIGN, SETTING, AND PARTICIPANTS: One thousand three hundred thirty-six normal comparison (NC), 583 dementia (420 AD, 111 non-AD dementia, and 52 mixed AD with non-AD dementia), and 250 MCI (223 amnestic and 27 nonamnestic MCI) individuals living in the community were included (all aged 60 years and older). RESULTS: Both TS-I and TS-II were highly correlated with other global cognitive and functional scales. Both total scores showed, though modest, superior NC versus MCI discrimination ability to Mini-Mental State Examination (MMSE). Their discrimination ability for NC versus dementia was excellent and significantly better, especially in discriminating very mild dementia, than MMSE. The addition of frontal-executive test score to TS-I or TS-II did not make a significant improvement in dementia or MCI discrimination ability. Both of them also showed higher test-retest and interrater reliability than MMSE or any individual neuropsychological tests in the CERAD-NP. CONCLUSION: These results strongly support the validity and usefulness of CERAD total scores for early detection and progression monitoring of MCI and dementia in clinical and research settings.

Disrupted sleep maintenance is associated with altered circadian phase and phase angle in community-dwelling adults.

OBJECTIVE: We aimed to compare the sleep onset, dim light melatonin onset (DLMO) and phase angle (PA) between sleep onset and DLMO of insomnia patients with those of controls, and to examine the difference in these parameters in relation to objective sleep quality. METHODS: Participants were recruited from three Public Health Centers in Korea. Actigraphy recordings were conducted for seven days. Five hourly saliva samples were obtained from three hours prior to sleep onset. A total of 48 controls and 64 insomnia patients were analyzed. Nocturnal sleep parameters, DLMO, and PA were compared between the controls and insomnia patients, and between the controls and patients with difficulty in maintaining sleep (DMS). These sleep and circadian parameters were compared among the subgroups divided by wake after sleep onset (WASO) amount. RESULTS: There were no significant differences in sleep parameters between the control and insomnia groups, and between the controls and DMS subgroup. The sleep onset, DLMO, and PA of the insomnia group or those of DMS subgroup were not different from those of controls. There were significant differences in the sleep onset and DLMO (p < 0.05) among mild, moderate, and severe WASO groups. A regression analysis revealed the earlier DLMO and shorter PA predicted the severity of WASO (p < 0.0001) in total participants. CONCLUSIONS: Insomnia patients exhibited no difference in their sleep timing and melatonin rhythm compared to controls. However, these circadian parameters varied depending on the severity of WASO, and advanced melatonin phase and its shortened phase angle were associated with worsening of sleep maintenance.

Association of rest-activity and light exposure rhythms with sleep quality in insomnia patients.

The relevance of altered rest-activity rhythm (RAR) and light exposure rhythm (LER) in insomnia patients under natural conditions remains unclear. The aim of this study was to compare the parametric and nonparametric circadian variables of RAR and those of LER under natural conditions between insomnia patients and normal controls (NC) in a community-dwelling setting. The relationship of the nonparametric variables with sleep quality was also explored in both groups. Participants above 18 years old were recruited from three Public Health Centers in a rural area of Korea. Actigraphy (Actiwatch 2; Philips Respironics, Murrysville PA, USA) recording was conducted for 7 days. Subjects were eligible for our study if they had an insomnia disorder (ID) for at least 1 month. Actigraphy data of 78 normal control (NC) subjects (Age, 55.95 ± 13.22 years) and 104 patients with insomnia disorder (ID) (Age, 62.14 ± 12.34 years) were included for the analysis. Acrophases and amplitudes of RAR and LER were estimated using cosinor analysis. Interdaily stability (IS), intradaily variability (IV), and relative amplitude (RA) of these rhythms were determined using nonparametric methods. Parametric cosinor and nonparametric variables of RAR and LER were compared between the NC and ID groups. Generalized linear models (GLMs) were applied to evaluate the main effects of group and each nonparametric variable as well as a group by each variable interaction on the sleep onset latency (SOL), sleep efficiency (SE), and wake after sleep onset (WASO) reflecting sleep quality. Among sleep parameters, the ID group showed significantly lower SE and greater WASO than the NC group. There were no significant differences in the acrophase and amplitude of RAR and LER between the two groups. There were no significant differences in IV, IS, and RA of RAR and LER between the two groups either. GLMs for RAR revealed a significant interaction between the group and IS on the SOL (ß = -46.39, p < 0.01), indicating a negative relationship of the IS with SOL in ID unlike its positive relationship in NC. There were no significant main effects of IV on the SOL, SE, and WASO, but significant main effects of RA on the SE and WASO (ß = 63.65 and ß = -221.43, respectively, p < 0.01). GLMs for LER revealed no significant main effects of IS, IV or RA on the SOL, SE, and WASO, but significant interactions between group and RA on the SE and WASO (ß = 56.17 and ß = -171.93, respectively, p < 0.05), indicating a stronger positive relationship of the RA with SE in ID compared to NC, and a negative relationship of the RA with WASO in ID, unlike its positive relationship in NC. Although our study did not reveal group differences in circadian variables of RAR and LER, it suggested that the regularity of RAR could be positively associated with sleep initiation, while the robustness of LER could be positively associated with sleep maintenance in insomnia patients.

Psychological Screening for Exceptional Environments: Laboratory Circadian Rhythm and Sleep Research.

Selecting participants who constitute a representative sample while protecting them from potential adverse outcomes is a concern for clinical researchers. Our research group conducts deep phenotyping studies of the circadian timing system and sleep-wake regulation in long (up to 3 months) laboratory experiments, similar in many ways to "exceptional environment" conditions. Here, we describe the psychological screening process we have used for more than 30 years. We outline our "Select In" and "Select Out" measures within three major categories: psychological, psychophysiological, and psychosocial factors. We describe the screening process, inclusion-exclusion criteria on standard questionnaires, and clinical interview questions. We also describe how we manage the exclusion process during screening, ensure continued psychological health during the laboratory study, and manage study terminations. We present data from one recent study, outlining the number of individuals excluded at each stage of the process and present subjective mood data from the included individuals, showing the trajectory of mood across the five-week laboratory study and the end-of-study debriefing, during which the participants rated their comfort with various aspects of the study and their willingness to return for a future study. While designed for our inpatient research studies, elements of these procedures may also be useful for selecting individuals for other exceptional environments.

The prevalence of cognitive impairment with no dementia in older people: the Seoul study.

OBJECTIVE: This study aimed to estimate prevalence of cognitive impairment with no dementia (CIND) in older people. It was conducted in an urban area of Korea, Seoul, and employed a two-stage design for case identification. METHODS: Overall 643 persons aged 65 years and older participated and 217 persons sampled from the three levels of performance of MMSE underwent a second stage clinical evaluation. CIND was diagnosed when the global Clinical Dementia Rating (CDR) index was 0.5 and the Diagnostic and Statistical Manual of Mental Disorders, 4th edition diagnostic features of dementia were not satisfied. CIND cases without any apparent causes were classified as CIND of unidentified cause (CIND(uc)). RESULTS: CIND prevalence ranged from 26.3% in persons aged 65-69 to 46.5% in persons aged 85 years and older. The age-standardized prevalence for overall CIND was 31.9% and for CIND(uc) 19.2%. The prevalences of CIND for the three severity grade were 15.8%, 9.7%, and 6.2% for CDR sum of boxes scores of 0.5, 1-1.5, and >or=2, respectively. CONCLUSIONS: The prevalence of CIND in community-residing elderly is probably higher than previously reported. The results of this study are useful for assessments of present and future demands for healthcare services.

Phase Shifts to a Moderate Intensity Light Exposure in Older Adults: A Preliminary Report.

Age-related disrupted sleep has been associated with modifications in the timing of endogenous circadian rhythms. There are studies suggesting a decreased sensitivity of the aging circadian pacemaker to light. In this study, we aimed to test whether a moderate illuminance light stimulus would produce significant phase shifts in older adults, and whether those would fall in a range consistent with the illuminance response curve (IRC) we previously reported in older adults. We conducted an 8-day in-patient study with 12 healthy older participants (mean age [SD], 58.3 [4.2] y, 5 females). A 6.5-h polychromatic white light exposure with a target illuminance of 270 lux was administered beginning in the early biological night. Before and after the light exposure, a circadian phase estimation procedure was carried out, with plasma melatonin data used as a circadian phase marker. The mean phase delay produced by the light stimulus was 1.78 ± 0.77 h. Ten of the 12 phase delay shifts at ~270 lux fell within the 95% predictive interval of the model fit to data from our previous IRC in older adults. This finding demonstrates that the circadian system of healthy older adults is sensitive to the phase-delaying effects of a moderate intensity light stimulus. The magnitude of the observed phase shifts is consistent with the previously described IRC in older adults.

Characteristics of napping in community-dwelling insomnia patients.

OBJECTIVE: We aimed to determine napping characteristics of community-dwelling patients with insomnia disorder (ID) compared to characteristics of normal controls (NC), and to examine the effect of napping on nocturnal sleep. METHODS: Adult volunteers who were more than 18 years old were recruited from three rural public health centers in Korea. Data from actigraphy recording and a sleep diary filled out for seven days were obtained. Finally, 115 ID patients and 80 NC subjects were included in this study. Parameters and timing of nocturnal sleep and nap were compared between the ID and NC groups. Two-way analysis of covariance (ANCOVA) was performed to determine the effect of ID diagnosis and napping on sleep parameters. RESULTS: Sleep efficiency (SE) in the ID group was significantly lower (p = 0.010), and wake time after sleep onset (WASO) was significantly greater (p = 0.023), compared to the NC group. There was no significant difference in nocturnal sleep or nap timing between the two groups. Nap frequency in the ID group was significantly higher than that in the NC group (p = 0.025). Although ID diagnosis and napping had no independent effect on fragmentation index, their interaction had a significant effect on fragmentation index (p = 0.021). Nap frequency was positively correlated with PSQI score (r = 0.166, p = 0.033). CONCLUSION: Insomnia patients showed no significant difference in nap timing or nap duration compared to NC subjects. However, insomnia patients showed higher nap frequency. Frequent napping was associated with poorer subjective sleep quality. Therefore, although napping might not have a negative impact on nocturnal sleep maintenance in NC subjects, it did have an effect on nocturnal sleep in insomnia patients.

A secondary analysis of racial differences in periodic leg movements in sleep and ferritin in hemodialysis patients.

BACKGROUND AND OBJECTIVE: Hemodialysis (HD) is associated with restless legs syndrome (RLS) and periodic leg movements in sleep (PLMS), but the mechanisms underlying these relationships remain unclear. African-American HD patients have been reported previously to have a reduced likelihood of RLS. Alterations in iron metabolism, known to be a risk factor for idiopathic forms of RLS, could represent the basis for these racial differences. PATIENTS AND METHODS: In secondary data analyses from a previously published study, we examined raw and log-transformed values for plasma ferritin and polysomnographically recorded PLMS in Caucasian and African-American HD patients. RESULTS: African-American (n=36) HD patients had higher ferritin and lower PLMS than Caucasians (n=10). However, within the African-American population, ferritin levels were unrelated to PLMS. CONCLUSIONS: These results are compatible with previously reported racial differences in RLS to the extent that PLMS were less common in the African-American population. However, they suggest that if a differential genetic vulnerability underlies those racial differences, it may not manifest as a deficiency in iron metabolism, at least within the constraints of the marker of iron stores used here (e.g. serum ferritin) and in the specific population studied (hemodialysis). Future studies with larger, more representative samples of African-Americans and Caucasians will be required to replicate such differences.

Sleep apnea, coronary artery disease, and antioxidant status in hemodialysis patients.

BACKGROUND: It recently was suggested that sleep apnea syndrome (SAS) is associated with the cardiovascular complications and outcomes seen in patients with end-stage renal disease (ESRD). This study investigates the association of SAS with coronary artery disease and antioxidant status in patients with ESRD. METHODS: Twenty-six hemodialysis patients underwent overnight polysomnography to evaluate sleep parameters. We performed multirow spiral computed tomography to derive coronary artery calcification (CAC) scores as an indicator of the severity of coronary artery disease and measured predialysis serum total antioxidant status (TAS) as a marker of antioxidant defenses. RESULTS: Nine of 26 patients had normal to mild SAS with an apnea-hypopnea index (AHI) less than 15, 9 patients had moderate SAS with an AHI of 15 to 30, and the remaining 8 patients had severe SAS with an AHI greater than 30. AHI and oxygen desaturation index (ODI) were strongly interrelated (r = 0.754; P < 0.001). CAC severity was associated with SAS severity: median CAC scores increased (P = 0.009) with increasing AHI category. However, values for TAS were not significantly different among the 3 AHI categories. CAC score also correlated positively (r = 0.564; P = 0.003) with ODI, and TAS correlated negatively (r = -0.539; P = 0.005) with ODI. CONCLUSION: These results suggest that frequent oxygen desaturation triggered by SAS is associated with severe coronary artery disease and decreased antioxidant status in patients with ESRD. However, conclusions from this study should be drawn with caution because of its methodological limitations (cross-sectional design, heterogeneity of study population, and small number of patients).

The Effect of Choline Acetyltransferase Genotype on Donepezil Treatment Response in Patients with Alzheimer's Disease.

OBJECTIVE: We examined the difference in responses to donepezil between carriers and non-carriers of the A allele at the +4 position of the choline acetyltransferase (ChAT) gene in Koreans. METHODS: Patients who met the criteria for probable Alzheimer's disease (AD) (n=199) were recruited. Among these, 145 completed the 12-week follow-up evaluation and 135 completed the 26-week scheduled course. Differences and changes in the Korean version of the mini-mental state examination (MMSE-KC) score, Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Neuropsychological Assessment Battery (CERAD-K[N]) wordlist subtest score (WSS), CERAD-K(N) total score (TS), and the Korean version of geriatric depression scale (GDS-K) score between baseline and 12 weeks or 26 weeks were assessed by the Student's t-test. RESULTS: At 12 weeks, the changes in the MMSE-KC score, CERAD-K(N) WSS, and CERAD-K(N) TS from baseline were not significant between ChAT A allele carriers and non-carriers; however, at 26 weeks, these changes were significantly larger in ChAT A allele carriers than in non-carriers (p=0.02 for MMSE-KC and p=0.03 for CERAD-K(N) WSS respectively). CONCLUSION: Our findings in this study suggested that presence of the A allele at the +4 position of ChAT might positively influence the treatment effect of donepezil in the early stages of AD in Koreans.

The prevalence of dementia in older people in an urban population of Korea: the Seoul study.

OBJECTIVES: To estimate prevalence of dementia and its subtypes in older people in Seoul, a metropolitan area of Korea, and compare these findings with estimates reported for other populations. DESIGN: The study employed a two-stage design for case identification. Initially, the Mini-Mental State Examination in the Korean version (MMSE-KC) of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) assessment packet was administered to all participants. Two hundred seventeen persons sampled from three levels of performance on MMSE-KC underwent the second-stage clinical evaluation based on the Korean Version of the CERAD assessment packet. SETTING: The study was conducted in an urban community setting. PARTICIPANTS: Six hundred forty-three persons aged 65 and over participated in the study. MEASUREMENTS: Dementia was defined using the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition diagnostic features of dementia. RESULTS: Dementia prevalence ranged from 2.6% in persons aged 65 to 69 to 32.6% in persons aged 85 and older. Age-standardized prevalence was 8.2% for dementia, 5.4% for Alzheimer's disease, and 2.0% for vascular dementia. The prevalence estimates, which excluded very mild cases (clinical dementia rating index 0.5), were approximately 5.3% for dementia and 4.3% for Alzheimer's disease. CONCLUSION: The prevalence of dementia in older people in Seoul appears to be somewhat lower than in rural areas of Korea. Considering the difficulties involved in establishing a diagnostic threshold for dementia, actual differences in dementia prevalence between Asian populations are probably minimal.

Reliability and validity of the Korean version of Morningness-Eveningness Questionnaire in adults aged 20-39 years.

Morningness-Eveningness (ME) can be defined by the difference in individual diurnal preference observed from general behavioral patterns including sleep habits. The Horne & Östberg Morningness-Eveningness Questionnaire (MEQ) has been used for classifying ME types. We examined the reliability of a Korean version of the MEQ (Korean MEQ) and verified its validity by comparing responses on the Korean MEQ to objectively-recorded sleep-wake rhythms. After translating and back translating the MEQ from English into Korean, we examined the internal consistency of 19 items of the Korean MEQ in 91 subjects, and the test-retest reliability in 21 subjects who took the Korean MEQ twice, 4 weeks apart. The Korean MEQ was then administered to 1022 young adult subjects. A subset of 46 morning, neither, and evening type subjects took part in a validation study in which their rest-activity timing was collected by actigraphy for 7 days. Cosinor analyses on these data were done to obtain the acrophase and amplitude of the sleep-wake rhythm. Cronbach's alpha of the total scores from the Korean MEQ was 0.77, and the test-retest reliability intra-class correlation coefficient was 0.90 (p < 0.0001). There was a significant negative correlation between Korean MEQ score and reported sleep-wake timing among the entire cohort (p < 0.0001). There was a significant difference in bedtime and wake time (on both work and free days), and in the mean sleep-wake rhythm acrophase, between ME types (p < 0.01). In this study, the validity of the Korean MEQ was verified by illustrating the difference in acrophases of the sleep-wake rhythm between the ME types in young adults.