Shoichi Asaoka

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.

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.

Prevalence and clinical characteristics of restless legs syndrome in chronic kidney disease patients

OBJECTIVE To clarify the prevalence of restless legs syndrome (RLS) in the chronic kidney disease (CKD) population and determine the relationship between severity of renal dysfunction and risk of RLS as well as the impact of the disorder on mood and sleep disturbance, we conducted a questionnaire survey followed by face-to-face interviews with Japanese CKD patients. METHODS We sent a questionnaire battery including demographics items, the National Institutes of Health/International RLS Study Group (IRLSSG) consensus questionnaire, the Center for Epidemiological Studies Depression Scale, and the Pittsburgh Sleep Quality Index to eligible CKD patients (n=514) and age- and sex-matched controls (n=535). Structured interviews were performed for the diagnosis of RLS. RESULTS The prevalence of positive RLS in the CKD subjects was significantly higher than that in the controls (3.5% vs. 1.5%, p=0.029). The proportion of renal failure (RF) in CKD subjects with RLS was significantly higher than in those without RLS, and multiple logistic regression analysis revealed that the presence of RLS symptoms was associated only with the existence of RF. In addition, the presence of both RLS and CKD was significantly associated with the presence of depression and sleep disturbance. CONCLUSIONS The risk of RLS in the CKD population was higher than that in the general population and increased with the progression of renal dysfunction. Additionally, the existence of RLS might play a role in an increased risk for developing depression and sleep disturbance in the CKD population.

Excessive Daytime Sleepiness among Japanese Public Transportation Drivers Engaged in Shiftwork

Objective: To explore the actual condition of sleep disorders underlying subjective excessive daytime sleepiness (EDS) among train and bus drivers engaged in shiftwork. Methods: This study targeted 3109 public transportation drivers. Clinical diagnoses were made based on 147 drivers who claimed to have subjective EDS, and 285 drivers who were judged to have obstructive sleep apnea syndrome (OSAS), based on the screening process. Results: Among these subjects, the prevalence of OSAS was 3.7% and that of shiftwork disorder (SWD) was 1.5%. SWD was common among drivers who had EDS (32.7% of drivers with EDS), and their EDS severity was higher than that of OSAS drivers. The drivers with SWD were mostly young and neither obese nor hypertensive. Conclusions: Encouraging awareness of SWD and OSAS could be necessary to prevent sleepiness-related accidents.

The effects of a nighttime nap on the error-monitoring functions during extended wakefulness.

STUDY OBJECTIVES To examine the effects of a 1-hr nighttime nap, and the associated sleep inertia, on the error-monitoring functions during extended wakefulness using the 2 event-related potential components thought to reflect error detection and emotional or motivational evaluation of the error, i.e., the error-related negativity/error-negativity (ERN/Ne) and error-positivity (Pe), respectively. DESIGN Participants awakened at 07:00 the morning of the experimental day, and performed a stimulus-response compatibility (arrow-orientation) task at 21:00, 02:00, and 03:00. SETTING A cognitive task with EEG data recording was performed in a laboratory setting. PARTICIPANTS Twenty young adults (mean age 21.3 ± 1.0 yr, 14 males) participated. INTERVENTIONS Half of the participants took a 1-hr nap, and the others had a 1-hr awake-rest period from 01:00-02:00. MEASUREMENTS AND RESULTS Behavioral performance and amplitude of the Pe declined after midnight (i.e., 02:00 and 03:00) compared with the 21:00 task period in both groups. During the task period starting at 03:00, the participants in the awake-rest condition reported less alertness and showed fewer correct responses than those who napped. However, there were no effects of a nap on the amplitude of the ERN/Ne or Pe. CONCLUSIONS Our results suggest that a 1-hr nap can alleviate the decline in subjective alertness and response accuracy during nighttime; however, error-monitoring functions, especially emotional or motivational evaluation of the error, might remain impaired by extended wakefulness even after the nap. This phenomenon could imply that night-shift workers experiencing extended wakefulness should not overestimate the positive effects of a nighttime 1-hr nap during extended wakefulness.

The factors associated with preferences for napping and drinking coffee as countermeasures for sleepiness at the wheel among Japanese drivers

OBJECTIVE We explored differences between professional and non-professional drivers in terms of the factors associated with preferences for generally accepted, effective countermeasures for sleepiness at the wheel--i.e., napping and drinking coffee. METHODS We performed a cross-sectional questionnaire survey. Data from professional (n = 716) and non-professional (n = 3365) drivers were used for analyses. RESULTS The results showed that professional drivers experienced drowsy driving and traffic accidents due to falling asleep more often than non-professional drivers. Multiple logistic regression analyses showed that variables which may act as aggravating factors for sleepiness (i.e., engagement in shift-work and insufficient sleep) were associated with preferences for these countermeasures among non-professional drivers. In contrast, among professional drivers, being male and having experienced traffic accidents due to drowsy driving were associated with a preference for napping, while longer annual driving distances and shorter periods after the acquisition of driving licenses were associated with drinking coffee. CONCLUSION Our results suggest that non-professional drivers are likely to take these effective countermeasures when they feel or have the potential to experience sleepiness at the wheel. However, this tendency was not observed in professional drivers, and it is speculated that they do not use naps as a countermeasure until they have experienced traffic accidents due to drowsy driving. Sleep education for professional drivers and their employers is desirable for preventing drowsy driving-related traffic accidents.

Change in frequency of periodic limb movements during sleep with usage of continuous positive airway pressure in obstructive sleep apnea syndrome

Periodic limb movements during sleep (PLMS) sometimes newly appear on the night of continuous positive airway pressure (CPAP) titration in patients with obstructive sleep apnea syndrome (OSAS). To ascertain the incidence and causative factors of this phenomenon, we investigated differences in its prevalence and the factors associated with newly appeared and persistent PLMS on CPAP titration night. We retrospectively analyzed polysomnographic data of 997 consecutive OSAS outpatients who had undergone overnight CPAP titration. On the basis of changes in periodic limb movements index (PLMI) values (cut off level≥15/h) from baseline polysomnography (BPSG) to CPAP titration PSG, patients were assigned to one of four groups: persistent, CPAP-emergent, CPAP-disappeared, and non-PLMS. The rate of patients was 6.7% in the persistent group, 8.0% in the CPAP-emergent group, 4.0% in the CPAP-disappearance group, and 81.2% in the non-PLMS group. Multivariate logistic regression analysis revealed that a higher apnea-hypopnea index (AHI) on BPSG and ≥47years of age appeared to be associated with the CPAP-emergent group. The results suggest that elderly patients with higher AHI at BPSG may present with CPAP-emergent PLMS.

Factors Associated with Long-Term Use of Hypnotics among Patients with Chronic Insomnia

This study investigated factors associated with long-term use of benzodiazepines (BZDs) or benzodiazepine receptor agonists (BzRAs) as hypnotics in patients with chronic insomnia. Consecutive patients (n = 140) with chronic insomnia were enrolled in this study (68 men and 72 women; mean age, 53.8±10.8 years). All patients filled out a self-assessment questionnaire asking clinical descriptive variables at the baseline of the treatment period; patients received the usual dose of a single type of BZD or BzRA. The Pittsburgh Sleep Quality Index (PSQI) and the Zung Self-Rating Depression Scale were self-assessed at the baseline, and the former was re-evaluated at the time of cessation of medication or at the end of the 6-month treatment period. The PSQI included the following sub-items: evaluating sleep quality (C1), sleep latency (C2), sleep duration (C3), habitual sleep efficiency (C4), frequency of sleep disturbance (C5), use of sleeping medication (C6), and daytime dysfunction (C7). Among the patients, 54.6% needed to continue hypnotics for a 6-month treatment period. Logistic regression analysis revealed that, among descriptive variables, only the PSQI score appeared as a significant factor associated with long-term use {odds ratio (OR) = 2.8, 95% confidence interval (CI) = 2.0–4.0}. The receiver operating curve (ROC) analysis identified that the cut-off PSQI total score at the baseline for predicting long-term use was estimated at 13.5 points (area under the curve = 0.86, 95% CI = 0.8–0.92). Among the sub-items of PSQI, the increases in C1: (OR = 8.4, 95% CI = 2.4–30.0), C3: (OR = 3.6, 95% CI = 1.1–11.5), C4: (OR = 11.1, 95% CI = 3.6–33.9), and C6: (OR = 3.4, 95% CI = 1.9–6.2) scores were associated with long-term use. This study revealed that a high PSQI score at the baseline, particularly in the sub-items relating to sleep maintenance disturbance, is predictive of long-term hypnotic treatment. Our results imply the limitation of the effectiveness of hypnotic treatment alone for chronic insomnia.

Impact of hypnotics use on daytime function and factors associated with usage by female shift work nurses

OBJECTIVE We investigated quality of life (QOL) and work performance of hypnotics users, and explored the factors associated with multiple hypnotics usage in shift work nurses. METHODS We conducted a questionnaire-based, cross-sectional survey on nurses in university hospitals. We analyzed responses from 1202 nurses; 997 were female shift work nurses (82.9%), including 696 and 281 two- and three-shift workers, respectively. RESULTS The rate of hypnotics use was 10% (6.9% were single hypnotic users and 3.1% were multiple hypnotics users). The rate of insomnia did not differ between the single and multiple hypnotics users. However, multiple hypnotics users showed lower QOL, more severe depressive symptoms, and greater frequencies of work-related errors than those using a single hypnotic. A multiple logistic regression analysis revealed that age ≥27 years, presence of depression, eveningness chronotype, and presence of insomnia symptoms were significantly associated with hypnotics use. On the other hand, only the existence of shift work disorder (SWD) was significantly associated with usage of multiple hypnotics. CONCLUSIONS The present study suggested that usage of multiple hypnotics is not beneficial for relieving insomnia or for keeping better QOL in shift work nurses. It would be desirable to explore the causal relationship between SWD and multiple hypnotics use in a future longitudinal study.

Performance monitoring during sleep inertia after a 1-h daytime nap: Sleep inertia

Performance monitoring is an essential function involved in the correction of errors. Deterioration of this function may result in serious accidents. This function is reflected in two event‐related potential (ERP) components that occur after erroneous responses, specifically the error‐related negativity/error negativity (ERN/Ne) and error positivity (Pe). The ERN/Ne is thought to be associated with error detection, while the Pe is thought to reflect motivational significance or recognition of errors. Using these ERP components, some studies have shown that sleepiness resulting from extended wakefulness may cause a decline in error‐monitoring function. However, the effects of sleep inertia have not yet been explored. In this study, we examined the effects of sleep inertia immediately after a 1‐h daytime nap on error‐monitoring function as expressed through the ERN/Ne and Pe. Nine healthy young adults participated in two different experimental conditions (nap and rest). Participants performed the arrow‐orientation task before and immediately after a 1‐h nap or rest period. Immediately after the nap, participants reported an increased effort to perform the task and tended to estimate their performance as better, despite no objective difference in actual performance between the two conditions. ERN/Ne amplitude showed no difference between the conditions; however, the amplitude of the Pe was reduced following the nap. These results suggest that individuals can detect their own error responses, but the motivational significance ascribed to these errors might be diminished during the sleep inertia experienced after a 1‐h nap. This decline might lead to overestimation of their performance.