Yoko Komada

Factors Associated With Shift Work Disorder in Nurses Working With Rapid-Rotation Schedules in Japan: The Nurses’ Sleep Health Project

Workers who meet the criteria for shift work disorder (SWD) have elevated levels of risk for various health and behavioral problems. However, the impact of having SWD on shiftworkers engaged in rapid-rotation schedules is unknown. Moreover, the risk factors for the occurrence of SWD remain unclear. To clarify these issues, we conducted a questionnaire-based, cross-sectional survey on a sample of shiftworking nurses. Responses were obtained from 1202 nurses working at university hospitals in Tokyo, Japan, including 727 two-shift workers and 315 three-shift workers. The questionnaire included items relevant to age, gender, family structure, work environment, health-related quality of life (QOL), diurnal type, depressive symptoms, and SWD. Participants who reported insomnia and/or excessive sleepiness for at least 1 mo that was subjectively relevant to their shiftwork schedules were categorized as having SWD. The prevalence of SWD in the sampled shiftworking nurses was 24.4%; shiftworking nurses with SWD showed lower health-related QOL and more severe depressive symptoms, with greater rates of both actual accidents/errors and near misses, than those without SWD. The results of logistic regression analyses showed that more time spent working at night, frequent missing of nap opportunities during night work, and having an eveningness-oriented chronotype were significantly associated with SWD. The present study indicated that SWD might be associated with reduced health-related QOL and decreased work performance in shiftworking nurses on rapid-rotation schedules. The results also suggested that missing napping opportunities during night work, long nighttime working hours, and the delay of circadian rhythms are associated with the occurrence of SWD among shiftworking nurses on rapid-rotation schedules. (Author correspondence: yuinoue@tokyo-med.ac.jp)

Relation between morningness–eveningness score and depressive symptoms among patients with delayed sleep phase syndrome

OBJECTIVES Depressive symptoms are observed in a relatively large series of patients with delayed sleep phase syndrome (DSPS). This study was undertaken to investigate the prevalence, characteristics, and factors associated with depressive symptoms among DSPS patients. METHODS This study targeted 90 consecutive patients (54 men, 27.1±9.2 years old) diagnosed as having DSPS. Demographic and clinical characteristics were assessed at their initial visit, including application of the Zung self-rating depression scale (SDS) and morningness-eveningness questionnaire. A series of logistic regression analyses were conducted to determine the factors associated with depressive symptoms (determined as SDS⩾48). RESULTS Sixty-four percent of the DSPS patients were in a moderate or severe depressive state. Diurnal variation, sleep disturbance, fatigue, and psychomotor retardation were the main depressive symptom items on SDS in the DSPS patients. Logistic regression analyses showed that SDS⩾48 was significantly associated with moderate and definite evening chronotype. In contrast, self-reported nocturnal sleep onset and offset times were not associated with depressive symptoms. CONCLUSIONS There is a high prevalence of depressive symptoms among the DSPS patients. The symptomatic structure of depressive symptoms in this population appears to differ from those of typical depression. Moreover, results of our study suggest that depressive symptoms are more associated with the preference of the evening chronotype rather than sleep-wake phase among DSPS patients.

Insomnia as a risk for depression: A longitudinal epidemiologic study on a Japanese rural cohort

OBJECTIVES To determine (1) whether insomnia is a factor related to the presence or persistence of depression for 2 years in the Japanese population and (2) which component of insomnia is associated with the presence of depression for 2 years in a rural cohort. METHOD This is a community-based longitudinal study. Two thousand eight hundred twenty-five people aged 20 years or older were evaluated at baseline, and of those participants, 1,577 (56%) were reevaluated after 2 years. During both surveys, the participants were asked to describe demographic variables and to fill out self-rating scales of insomnia (Pittsburgh Sleep Quality Index [PSQI]) and depressive symptoms (Center for Epidemiologic Studies Depression Scale). RESULTS The results of a multiple logistic regression analysis showed that depression (OR = 6.0; 95% CI, 4.4-8.0) and insomnia (OR = 2.1; 95% CI, 1.5-2.8) at baseline were significantly associated with the presence of depression at the follow-up. Most of the PSQI subscales, except for sleep duration and habitual sleep efficiency, were significantly associated (P < .01) with the presence of depression at the follow-up. In addition, the new appearance and repeated existence of depression at the follow-up were related to persistent insomnia (adjusted ORs = 7.0 and 3.3 [P < .001], respectively). A result of the receiver operating characteristic curve showed that persons with insomnia whose PSQI scores exceeded 8 points at the baseline were most likely to still have insomnia at the follow-up (cutoff point = 7.5). CONCLUSIONS On the basis of our results in a Japanese population, insomnia with high severity level could be a risk factor for the presence/persistence of depression in the long-term prognosis.

Quality of life in patients with narcolepsy with cataplexy, narcolepsy without cataplexy, and idiopathic hypersomnia without long sleep time: Comparison between patients on psychostimulants, drug-naïve patients and the general Japanese population

OBJECTIVE To assess the quality of life of patients with narcolepsy with cataplexy (NA-CA), narcolepsy without cataplexy (NA w/o CA), and idiopathic hypersomnia without long sleep time (IHS w/o LST) who were taking psychostimulant medication, and to ascertain which factors (including psychosocial and environmental variables) influence quality of life in this population. METHODS In total, 185 patients who had received regular treatment were enrolled in the study (NA-CA, n=83; NA w/o CA, n=48; IHS w/o LST, n=54). Patients were asked to complete questionnaires including the Short Form-36 Health Survey (SF-36), the Epworth Sleepiness Scale (ESS), and items concerning psychosocial and environmental variables. RESULTS All three diagnostic groups had significantly lower scores for most SF-36 domains compared with the Japanese normative data, and the ESS score was significantly reduced with treatment. Multiple logistic regression analyses revealed that several SF-36 domains were associated with the ESS score; autonomy in controlling own job schedule, experience of divorce or break up with a partner due to symptoms, experience of being forced to relocate or being dismissed due to symptoms, and perception of support from others. CONCLUSIONS The severity of subjective sleepiness and psychological and environmental variables influenced quality of life in patients with these hypersomnias of central origin.

Detecting deteriorated vigilance using percentage of eyelid closure time during behavioral maintenance of wakefulness tests.

Several researchers have investigated the relation between vigilance and ocular variables such as saccade, slow eye movement, pupil, blink, or eyelid closure. This study was undertaken to find the most effective indicator among these ocular variables for evaluating short-term (1 min) fluctuation of vigilance, and to investigate the ability of the most effective ocular variable for predicting deteriorated vigilance during behavioral maintenance of the wakefulness test (Oxford sleep resistance test: OSLER test). Nine healthy volunteers (two women, 19-30 years old, 23.4±3.9 years old) participated in this study. Ocular variables were recorded during the OSLER test at 10 A.M. and 2 P.M. before and after partial sleep deprivation (4h sleep). The periods during the OSLER test were divided into 1 min epochs. Each epoch was classified according to the number of consecutive missed responses. Decreased blink frequency and pupil diameter as well as increased percentage of eyelid closure time (PERCLOS) and slow eye movement were observed as the consecutive missed responses increased. Among these variables, PERCLOS showed the highest ability to detect occurrence of any missed response and three or more consecutive missed responses. Moreover, a missed response seldom occurred (0.2±0.2/20 trial/min) when PERCLOS was less than 11.5% per minute. Results suggest that, among the ocular variables, PERCLOS can prevent error or accident caused by low vigilance most effectively.

Comparison of clinical characteristics among narcolepsy with and without cataplexy and idiopathic hypersomnia without long sleep time, focusing on HLA-DRB1( *)1501/DQB1( *)0602 finding.

BACKGROUND Clinical characteristics of narcolepsy without cataplexy (NA w/o CA) and its relation to positivity of HLA-DRB1( *)1501/DQB1( *)0602 remain unclarified. We investigated clinical features of NA w/o CA, particularly addressing HLA-DRB1( *)1501/DQB1( *)0602. METHODS Comparisons of the Epworth Sleepiness Scale (ESS), multiple sleep latency test (MSLT) variables, rapid eye movement (REM)-related symptoms, and treatment response to psychostimulant medication were made for four patient groups (narcolepsy with cataplexy; NA-CA, NA w/o CA HLA-positive, NA w/o CA HLA-negative, and idiopathic hypersomnia without long sleep time; IHS w/o LST). RESULTS Mean sleep latency was significantly shorter and the rate of reduction of ESS after medication was lower in both NA-CA and NA w/o CA HLA-positive groups than those in the IHS w/o LST group. Among the three narcoleptic groups, the NA w/o CA HLA-negative group showed the lowest REM latency and the highest reduction rate of ESS after treatment. Neither these subjective and objective sleepiness measures nor the treatment response measure was significantly different between this group and the IHS w/o LST group. CONCLUSIONS In NA w/o CA, HLA-positivity might affect hypersomnia severity and REM propensity. The NA w/o CA HLA-negative group and the IHS w/o LST group exhibit equivalent hypersomnia severity.

Melatonin profile and its relation to circadian rhythm sleep disorders in Angelman syndrome patients

BACKGROUND Sleep problems are known to be common in Angelman syndrome (AS), a neurodevelopmental disorder which is associated with an abnormality of chromosome 15q11-q13. However, the circadian aspect of sleep disorders in AS and an effective treatment for the disorder have yet to be established. METHODS We elucidated the sleep-wake patterns of AS patients and its relationship to the serum melatonin levels. The serum melatonin levels of 15 AS patients were measured every 4h for one day and the values were compared with those of age-matched controls. We also examined the effectiveness of the oral administration of melatonin on AS patients with circadian rhythm sleep disorders (CRSD). RESULTS A total of eight of the 15 AS patients had CRSD (irregular sleep-wake type, n=4; free-running type n=2; delayed sleep phase type, n=2). The nighttime serum melatonin levels of the AS patients were significantly lower than those of the controls at the measured time points during the night. The nocturnal melatonin levels were comparably low both in AS patients with and without CRSD except for the cases with delayed sleep phase type, which showed normal but delayed peak melatonin level. Six out of eight CRSD cases were given a daily dose of 1mg of melatonin between 18:00 and 19:00 regularly for three months. After receiving the treatment, the sleep patterns improved in four cases. CONCLUSION This study revealed a high prevalence of CRSD in AS patients, which may be related to abnormal serum melatonin profiles.

Short sleep duration and long spells of driving are associated with the occurrence of Japanese drivers' rear-end collisions and single-car accidents

Sleepiness and fatigue are important risk factors for traffic accidents. However, the relation between the accident type and lack of sleep as well as spells of driving has not been examined sufficiently. This study aimed to clarify that short sleep duration and long spells of driving are more associated with rear‐end collisions and single‐car accidents as compared with accidents of other types in cases of people who cause accidents. After removing drunken driving as a cause of accidents, 1772 parties involved in accidents were questioned. The quantities of rear‐end collisions and single‐car accidents were, respectively, 240 and 293. Logistic regression analysis showed that short nocturnal sleep (<6 h) and 10‐min increments of spells of driving were significantly associated not only with rear‐end collisions but also with single‐car accidents as compared with accidents of other types. Furthermore, younger age (≤25 years old) and nighttime (21:00–06:00 h) driving were significantly associated with single‐car accidents as compared with accidents of other types. To prevent such accidents, countermeasures must be considered in light of the characteristics of drivers involved in each type of accident described above.

Difference in the characteristics of subjective and objective sleepiness between narcolepsy and essential hypersomnia

Abstract  The present study was conducted to investigate the difference in the characteristics of daytime sleepiness between narcolepsy and essential hypersomnia and to identify the relationship between the Epworth Sleepiness Scale (ESS) and the Multiple Sleep Latency Test (MSLT) in patients with these two disorders. Subjects consisted of 34 patients with essential hypersomnia (32.4 ± 11.0 years old), 52 patients with narcolepsy (29.0 ± 13.8 years old), and 45 control subjects (33.3 ± 6.6 years old). The subjects completed the ESS and underwent MSLT following a regular sleep‐wake schedule for over 2 weeks. The ESS scores were pathologically high and mean sleep latency on MSLT was short, not only in narcolepsy but also in essential hypersomnia. With respect to sleep latencies on each MSLT session, both essential hypersomnia and control subjects had the smallest value at 14:00, while narcolepsy lacked any statistical change at this time period. The correlation between ESS and mean sleep latency on MSLT was higher in essential hypersomnia than in narcolepsy, and the correlation was strongest for the session performed at 14:00. Based on the ESS and MSLT results, the severity of excessive daytime sleepiness was significantly milder in essential hypersomnia compared with that in narcolepsy. The results also indicate that diurnal variation of sleepiness was maintained, and the correlation between subjective and objective sleepiness was relatively maintained in essential hypersomnia compared to narcolepsy. It is suggested that the mild disease severity of essential hypersomnia contributed to the formation of these characteristics.

Gender Differences in the Clinical Characteristics Among Japanese Patients With Obstructive Sleep Apnea Syndrome

BACKGROUND Gender differences in the prevalence of various manifestations of obstructive sleep apnea syndrome (OSAS) is not as great as previously believed. The aim of the present study was to clarify the clinical patient characteristics of Japanese women and men with OSAS. METHODS A cross-sectional case-match control study was performed on patients from two sleep disorder centers. Two hundred forty-five women with OSAS were classified into premenopausal (n = 70) and postmenopausal (n = 175) groups. As well, 245 men matched for both age and apnea-hypopnea index (AHI) and another 245 men matched for age and body mass index (BMI) were established. We compared descriptive variables between genders in both the premenopausal and the postmenopausal female patient groups. RESULTS As a whole, female patients had significantly higher BMI than AHI-matched male patients (p < 0.05) and a significantly lower value of AHI than BMI-matched male patients (p < 0.001). Female patients had lower Epworth Sleepiness Scale scores than BMI-matched male patients (p < 0.05). On logistic regression analysis, presence of hypertension was significantly associated with BMI (>or=25 kg/m(2)), AHI (>or= 15 to < 30 events/h; >or= 30 to < 60 events/h; >or= 60 events/h), and presence of both hyperlipidemia and diabetes mellitus. However, gender differences were not associated with the occurrence of hypertension. Female patients had significantly lower optimal levels of continuous positive airway pressure than male patients. CONCLUSIONS Our results suggest that both the OSAS severity and the strength of pharyngeal closure is less in Japanese female patients than in male patients. Moreover, Japanese female patients are thought to have less daytime sleepiness than male patients but a similar rate of hypertension as male patients.