Takashi Haratani

Validation of the Karolinska sleepiness scale against performance and EEG variables

OBJECTIVE The Karolinska sleepiness scale (KSS) is frequently used for evaluating subjective sleepiness. The main aim of the present study was to investigate the validity and reliability of the KSS with electroencephalographic, behavioral and other subjective indicators of sleepiness. METHODS Participants were 16 healthy females aged 33-43 (38.1+/-2.68) years. The experiment involved 8 measurement sessions per day for 3 consecutive days. Each session contained the psychomotor vigilance task (PVT), the Karolinska drowsiness test (KDT-EEG alpha & theta power), the alpha attenuation test (AAT-alpha power ratio open/closed eyes) and the KSS. RESULTS Median reaction time, number of lapses, alpha and theta power density and the alpha attenuation coefficients (AAC) showed highly significant increase with increasing KSS. The same variables were also significantly correlated with KSS, with a mean value for lapses (r=0.56). CONCLUSIONS The KSS was closely related to EEG and behavioral variables, indicating a high validity in measuring sleepiness. SIGNIFICANCE KSS ratings may be a useful proxy for EEG or behavioral indicators of sleepiness.

Lifetime and 6-month prevalence of DSM-III-R psychiatric disorders in an urban community in Japan.

We conducted a community-based interview survey of a random sample of residents aged 20 years or older in an urban community in Japan using the University of Michigan Version of the WHO Composite International Diagnostic Interview for selected mood and anxiety disorders and alcohol abuse/dependence according to DSM-III-R. The final sample consisted of 1029 respondents (response rate, 57%). The lifetime and 6-month prevalences of selected mood, anxiety and alcohol use disorders were low in general. Alcohol abuse/dependence was more prevalent in men than in women. Younger respondents had a greater risk of generalized anxiety disorder and alcohol dependence. A greater risk of mood, anxiety and alcohol use disorders was observed among a recent birth cohort. We confirmed a lower prevalence of mood and anxiety disorders and alcohol use disorders in a community population in Japan than in Western countries, observations that were similar to previous ones in East-Asian countries. The patterns of demographic correlates and comorbidity are similar to those of most other countries.

Association of sickness absence with poor sleep and depressive symptoms in shift workers.

A cross-sectional study was conducted to evaluate the contribution of daily sleep habits and depressive symptoms to sickness absences of shift workers. A self-administered questionnaire that solicited answers about sleep, symptoms of depression, sickness absence, diseases/injuries, and lifestyle factors was submitted to a sample of 522 rotating shift workers between the ages of 18–59 (mean 27) yrs of an electric equipment manufacturing company. The seven features of sleep queried were daily hours of sleep, time to fall asleep, awakening during sleep, early morning awakening, sleep well at night, sufficiency of sleep, and excessive daytime sleepiness at work. The responses were assessed over the subjects previous 1-yr period. Each sleep feature, except daily sleeping hours, was dichotomized by the following responses: (1) taking more than 30 min to fall asleep (difficulty initiating sleep; DIS), (2) awakening during sleep almost every day (difficulty maintaining sleep; DMS), (3) early morning awakening almost every day (EMA), (4) sleeping very poorly or not so well at night, (5) definite or somewhat insufficient nightly sleep, and (6) excessive daytime sleepiness at work almost every day (EDS). Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. Sickness absence was calculated by asking subjects “How many days in total have you been absent from work due to sickness, including paid vacation, in the last 1-yr period?” The responses were divided into three groups that included no (0 days) sickness absences (reference group, n = 235 subjects), 1 to 4 days (short-term, n = 199 subjects), and 5 days or more (long-term, n = 88 subjects). Compared to the prevalence of sleep features of the reference group, workers with short-term absence showed a significantly higher prevalence of EMA with an odds ratio (OR) of 5.3, 95% confidence interval (CI) 1.3–22.0. Long-term absence was significantly associated with DMS (OR = 2.1, 95%CI 1.0–4.6), EMA (OR = 5.6, 95%CI 1.0–28.7), sleeping poorly at night (OR = 2.6, 95%CI 1.4–5.0), and high depressive symptoms (OR = 2.0, 95%CI 1.0–3.7) according to the CES-D score of ≥16, after adjusting for multiple confounding variables. These data point to an association between both the parameters of poor sleep and symptoms of deep depression when self-reported sickness absence is frequent. The association is particularly strong with long-term absence in male shift workers.

Coemergence of Insomnia and a Shift in the Th1/Th2 Balance toward Th2 Dominance

Objectives: Insomnia is associated with physical and mental disorders. We examined the effect of insomnia on immune functions, focusing on the T helper 1 (Th1)/ T helper 2 (Th2) balance, by a cross-sectional design. Methods: We provided a self-administered questionnaire to evaluate sleep habits, smoking and medical disorders to 578 men without any toxic exposure (20–64 years old), and measured natural killer (NK) cell activity in 324 men and production of interferon-gamma (IFN-γ) and interleukin-4 (IL-4) after stimulation with phytohemagglutinin in 254 men. According to the criteria of DSM-IV, in which insomnia is classified into primary and secondary insomnia, we assessed the effect of insomnia on immune functions, controlling for age and smoking in groups with and without medical disorders. Results: The prevalence of insomnia in the present study was 9.2%. In the absence of medical disorders, insomniac men had a significantly lower IFN-γ and ratio of IFN-γ to IL-4 than noninsomniac men. Men with insufficient sleep or difficulty initiating sleep (DIS) had a significantly lower IFN-γ to IL-4 ratio than those not suffering from insufficient sleep or DIS. In the presence of medical disorders, insomniac men had significantly higher IL-4 than noninsomniac men. Men with difficulty maintaining sleep (DMS) had a significantly lower IFN-γ to IL-4 ratio than men without DMS. NK cell activity was independent of insomnia. Conclusions: The present results showed a link between insomnia unrelated to medical disorders and a shift in the Th1/Th2 balance toward Th2 dominance, indicating that the relationship between sleep quality and the etiology of immune-related diseases should be reconsidered.

Psychosocial Work Characteristics Predicting Daytime Sleepiness in Day and Shift Workers

Characteristics of work organization other than working time arrangements may contribute importantly to daytime sleepiness. The present study was designed to identify the psychosocial factors at work that predict daytime sleepiness in a sample of day and shift workers. Participants working at a pulp and chemical factory completed an annual questionnaire regarding psychosocial factors at work using the U.S. National Institute for Occupational Safety and Health Generic Job Stress Questionnaire (i.e., quantitative workload, variance in workload, job control, support from supervisor, coworkers, or family/friends, job satisfaction, and depressive symptoms), as well as daytime sleepiness (through the Epworth Sleepiness Scale [ESS]) and sleep disturbances for three years starting in 2002 (response rates, 94.6–99.0%). The present analysis included 55 day workers (11 women) and 57 shift workers (all men) who participated in all three years of the study, worked under the same work schedule throughout the study period, and had no missing data on any of the daytime sleep items. A repeated‐measures analysis of covariance (ANCOVA) was used to test the effects of work schedule (day vs. shift work) and psychosocial factors at work in 2002 on the ESS scores in subsequent years, with sleep duration, insomnia symptoms, chronic diseases, and sleepiness levels at baseline as covariates. Given significant and near‐significant interactions of work schedules with psychosocial factor or study year, the ANCOVA, with the factors of psychosocial work characteristics and study year, was performed by type of work schedule. The results indicated a significant main effect of psychosocial work characteristics (p=0.010, partial ŋ2=0.14) and an almost significant main effect of study year (p=0.067, partial ŋ2=0.06) and interaction between psychosocial work characteristics and study year (p=0.085, partial ŋ2=0.06) for variance in workload among the day work group. The day workers reporting high variance in workload in 2002 exhibited significantly higher ESS scores in 2003 and 2004 than did those reporting low variance in workload. The ANCOVA for the shift work group showed a main effect of psychosocial work characteristics for job satisfaction (p=0.026, partial ŋ2=0.10) and depressive symptoms (p=0.094, partial ŋ2=0.06) with the interaction between psychosocial work characteristics and study year for job satisfaction (p=0.172, partial ŋ2=0.04) and depressive symptoms (p=0.035, partial ŋ2=0.07). The shift workers with low job satisfaction and high symptoms of depression in 2002 showed significantly greater ESS scores in 2003 and/or 2004 than did those with opposite characteristics. These results may suggest a potential predictive value of variance in workload for day workers as well as job satisfaction and depressive symptoms for shift workers with respect to daytime sleepiness. The present findings may imply that redesigning these aspects of work environment would be of help in managing daytime sleepiness.

Association of active and passive smoking with sleep disturbances and short sleep duration among Japanese working population

Background: The relationship between passive smoking and sleep is uncertain. Purpose: To examine the association of passive/active smoking with sleep disturbances. Method: 732 women and 1,896 men, working in a suburb of Tokyo, were surveyed using a self-administered questionnaire. Information on smoking, passive smoking exposure, and sleep was elicited. Exposure levels to passive smoking were assessed separately at work and at home as no, occasional, or regular exposure. Risk of sleep disturbances according to smoking status was estimated using logistic regression with odds ratios (OR) and 95% confidence intervals (CIs) as measures of association. Results: Compared to never smokers, odds of difficulty awakening in the morning (DAM) in current smokers were significantly higher for women (OR 1.95) and men (OR 1.50), while increased difficulty initiating sleep (OR 1.88) and decreased early morning awakening (OR 0.31) were found only in women. Never smoking men occasionally exposed to passive smoking at work but not at home had increased odds (OR 1.81) of short sleep duration (SSD, <6 h) than unexposed counterparts. Conclusions: The analyses suggest that exposure to passive smoking at work is associated with SSD in men, while current smoking relates to various subtypes of sleep disturbances in both sexes.

Correlates of Depressive Symptoms among Workers in Small- and Medium-scale Manufacturing Enterprises in Japan

Correlates of Depressive Symptoms among Workers in Small‐ and Medium‐scale Manufacturing Enterprises in Japan: Tomoko Ikeda, et al. Department of Nursing, School of Health Sciences, Ibaraki Prefectural University of Health Sciences

Job stressors and long-term sick leave due to depressive disorders among Japanese male employees: findings from the Japan Work Stress and Health Cohort Study

Background Research on the association between job strain or other job stressors and depressive disorders is still limited. The purpose of the present study was to investigate the prospective association of job strain, role stressors and job insecurity with long-term sick leave due to depressive disorders. Methods A prospective study was conducted of a total of 15 256 men aged 18–67 years with no previous history of mental disorders employed in six manufacturing factories located in several regions of Japan. At baseline, they were surveyed using a self-administered questionnaire, including self-reported measures of job strain, as well as its components (job overload and job control), role stressors (role ambiguity and role conflict), social support at work, job insecurity and other demographic and psychological covariates. During the follow-up, a long-term sick leave of 30 days or more due to depressive disorders was recorded. Results During 5.14 years of follow-up on average, 47 incident cases of sick leave of 30 days or more due to depressive disorders were observed. High job control at baseline was associated with a lower risk of long-term sick leave due to depressive disorders, after adjusting for demographic variables, depressive symptoms and neuroticism at baseline (hazard ratio 0.28, 95% CI 0.11 to 0.71); high role ambiguity was associated with the higher risk (hazard ratio 3.49, 95% CI 1.43 to 8.49). Conclusion Job control and role ambiguity may be important predictors of long-term sick leave due to depressive disorders among male employees, independent of depressive symptoms and neuroticism.

The prevalence and correlates of occupational injuries in small-scale manufacturing enterprises.

The Prevalence and Correlates of Occupational Injuries in Small‐Scale Manufacturing Enterprises: Akinori Nakata, et al. National Institute of Occupational Safety and Health—Workers involved in small‐scale manufacturing businesses are known to comprise a high‐risk population for occupational injury. The present study investigated the prevalence and correlates of occupational injury in this population. A self‐administered questionnaire that solicited answers about occupational information including injury, demographic characteristics, health conditions and lifestyle factors was collected from a sample of 1,298 workers in 228 small‐scale manufacturing enterprises (defined as fewer than 50 workers) aged 16–78 (mean 46) yr in Yashio city, Saitama, Japan (response rate 65.5%). The enterprises were randomly selected from the 2000 edition of the city commercial directory corresponding to the distribution of types of businesses in the city. Occupational injury was assessed by asking subjects, ‘Have you ever been injured during your work, including minor scratches and cuts in the previous 1‐yr period?’ The possible response was either ‘yes’ or ‘no.’ The prevalence of study‐defined occupational injury among the workers was 35.6% (male 43.0%, female 17.9%). Among job types, manufacturing (44.2%) and driving (43.5%) had high rates of occupational injuries. Similarly, occupational injuries were high in the papermaking (54.5%) and machinery (47.7%) industries. For males, younger age, current or former smoking, insomnia symptoms, and disease(s) currently under treatment were correlated with injury, whereas for females, being unmarried, higher educational status, and insomnia symptoms were the correlating factors. Occupational injury is common among small‐scale manufacturing businesses, and is associated with multiple controllable factors. Countermeasures such as prohibiting smoking during work, sleep health education, job safety training for young/inexperienced workers are appropriate methods for eliminating or reducing injuries.

Prevalence and demographic correlates of alcohol-related problems in Japanese employees

SummaryTo examine the relationship of basic sociodemographic characteristics to alcohol-related problems in Japanese employees, a questionnaire survey was conducted of a total of 2,581 employees of a computer factory in a suburb of Tokyo. The questionnaires included items on gender, age, marital status, social class (i. e., education, family income and occupation), alcohol consumption, and the Kurihama Alcoholism Screening Test (KAST). Data from 1098 male and 265 female current drinkers aged 20 years or older were analyzed; 15% and 6% of the male and female subjects, respectively, were classified as having alcohol-related problems on the basis of the KAST score (13% and 4% of the entire study population, respectively). Multiple logistic regression analysis indicated that alcohol-related problems were more prevalent in the less educated, managers and those who had a high alcohol consumption. The results suggested that education and occupation are important factors related to alcoholrelated problems in Japanese employees.