Masumi Minowa

Psychometric assessment of subjective sleep quality using the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J) in psychiatric disordered and control subjects

Subjective sleep quality has been identified as an important clinical construct in psychiatric disordered patients. The Pittsburgh Sleep Quality Index (PSQI), one of the most widely used standardized measures to assess subjective sleep quality, generates a global score and scores seven components. The present study psychometrically assessed clinical profiles of subjective sleep quality in 82 control and 92 psychiatric disordered subjects (primary insomnia, n=14; major depression, n=30; generalized anxiety disorder, n=24; and schizophrenia, n=24), using the Japanese version of the Pittsburgh Sleep Quality Index (PSQI-J). The overall reliability coefficient of the PSQI-J was high (Cronbachs alpha=0.77). Correlation coefficients between the PSQI-J global and component scores were statistically significant. The PSQI-J global and component mean scores were significantly higher in psychiatric disordered subjects than control subjects, except for the component of sleep duration. Using a cut-off point of 5.5 in the PSQI-J global score, estimations of sensitivity and specificity provided 85.7 and 86.6% for primary insomnia, 80.0 and 86.6% for major depression, 83.3 and 86.6% for generalized anxiety disorder, and 83.3 and 86.6% for schizophrenia, respectively. The present study supports the utility of the PSQI-J as a reliable and valid measure for subjective sleep quality in clinical practice and research.

Sleep loss and daytime sleepiness in the general adult population of Japan

There are few epidemiological studies on sleep loss and daytime sleepiness in the general adult population of Japan. A total of 4000 adult people, aged 20 and over, were randomly drawn from five areas of Japan, and 3030 individuals were interviewed and completed a questionnaire including information about sleep duration and sleep problems. Overall, 29% slept less than 6 h at night, 23% reported having insufficient sleep, and 6% took sleep enhancing medications. The prevalence rates were 21% for symptoms of insomnia and 15% for excessive daytime sleepiness. Symptoms of insomnia were more prevalent in the elderly, whereas young people were more likely to report short sleep duration, subjective insufficient sleep and excessive daytime sleepiness. A multiple logistic regression model revealed that excessive daytime sleepiness had significant associations with young people, short sleep duration, insomnia symptoms, subjective insufficient sleep and sleep enhancing medication use. Short sleep duration was the strongest predictor of excessive daytime sleepiness. The findings indicate that sleep loss and excessive daytime sleepiness in the Japanese adult population are common, and comparable to those reported in Western countries. Excessive daytime sleepiness in the general adult population seems more likely to be attributed to short sleep duration.

Factor structure of the 12‐item General Health Questionnaire in the Japanese general adult population

Abstract The 12‐item General Health Questionnaire (GHQ‐12) has been extensively used in a variety of settings across countries. The main aim of the present study was to assess the factor structure of the GHQ‐12 for the Japanese general adult population. Data came from a sample of 1808 Japanese aged 20 years or older who were randomly selected based on the 1995 census (897 men and 911 women). Cronbachs α coefficients were 0.83 for men and 0.85 for women. Overall, the corrected item‐total correlation coefficients were >0.20 for both genders. The GHQ‐12 yielded a two‐factor solution of psychological distress (items 2, 5, 6, 9, 10 and 11) and social dysfunction (items 1, 3, 4, 7 and 8), which jointly accounted for 49.1% of the total variance, for women. Item 12 on happiness was not discernable. For men, item 12 was separated from a social dysfunction factor and yielded the third factor with item 3 on social role, and the three factors jointly accounted for 57.6%. The results of the present study suggest that the GHQ‐12 can be used as an internally reliable and homogenous scale that produces mainly the factors of psychological distress and social dysfunction. Item 12 may be structurally different in the case of Japanese adults.

The association between use of mobile phones after lights out and sleep disturbances among Japanese adolescents: a nationwide cross-sectional survey.

STUDY OBJECTIVE The objective of this study was to examine the association between the use of mobile phones after lights out and sleep disturbances among Japanese adolescents. DESIGN AND SETTING This study was designed as a cross-sectional survey. The targets were students attending junior and senior high schools throughout Japan. Sample schools were selected by cluster sampling. Self-reported anonymous questionnaires were sent to schools for all students to fill out. PARTICIPANTS A total of 95,680 adolescents responded. The overall response rate was 62.9%, and 94,777 questionnaires were subjected to analysis. INTERVENTION N/A. MEASUREMENTS AND RESULTS Daily mobile phone use, even if only for a brief moment every day, was reported by 84.4%. Moreover, as for use of mobile phones after lights out, 8.3% reported using their mobile phone for calling every day and 17.6% reported using it for sending text messages every day. Multiple logistic regression analysis showed that mobile phone use for calling and for sending text messages after lights out was associated with sleep disturbances (short sleep duration, subjective poor sleep quality, excessive daytime sleepiness, and insomnia symptoms) independent of covariates and independent of each other. CONCLUSION This study showed that the use of mobile phones for calling and for sending text messages after lights out is associated with sleep disturbances among Japanese adolescents. However, there were some limitations, such as small effect sizes, in this study. More studies that examine the details of this association are necessary to establish strategies for sleep hygiene in the future.

Subjective sleep quality and sleep problems in the general Japanese adult population

To dimensionally describe subjective sleep quality using the Pittsburgh Sleep Quality Index (PSQI) and estimate the prevalence rate of sleep problems (PSQI global score > 5) in the general Japanese adult population, 1871 subjects randomly selected from the 1995 Census were examined. The PSQI component scores (mean ± SD) widely ranged (e.g. 0.04 ± 0.31 in hypnotic medication use for males aged 20–29 years, 0.03 ± 0.18 in hypnotic medication use for females aged 20–29 years, 1.10 ± 0.94 in sleep latency for males aged 80 or older, 1.52 ± 1.03 in sleep latency for females aged 80 or older). Statistical significance was found in each component score among age groups by gender. The PSQI global scores (mean ± SD) by age groups ranged from 4.00 ± 2.59 to 5.02 ± 3.89 for males (P < 0.39) and 4.30 ± 2.34 to 6.75 ± 4.10 for females (P < 0.001). The respective prevalence rates of sleep problems were 26.4% (95% CI = 23.6, 29.3) for males and 31.1% (95% CI = 28.1, 33.9) for females.

Gender differences in excessive daytime sleepiness among Japanese workers

Excessive daytime sleepiness (EDS) is serious concern in the workplace with respect to errors, accidents, absenteeism, reduced productivity and impaired personal or professional life. Previous community studies found a female preponderance of EDS, however, there is little research on EDS and gender in occupational settings. We examined the gender differences in prevalence and risk factors of EDS among employees working at a telecommunications company in the Tokyo metropolitan area. Our outcome measure of EDS was the Epworth Sleepiness Scale (ESS). A self-administered questionnaire on health and sleep including ESS was distributed to 5,571 workers between December 1999 and January 2000, and 5,072 responses were returned (91.0%). A total of 4,722 full-time, non-manual and non-shift employees aged 20-59 were used for analysis (3,909 men and 813 women). Chi-squared tests and multiple logistic regression analyses were applied for examining the gender differences in the prevalence and risk factors of EDS. The prevalence rates of EDS were 13.3% for women and 7.2% for men (P<0.001). We identified that deprived nocturnal sleep, an irregular sleep-wake schedule and depression were the risk factors of EDS for both genders, and being married worked as a protective factor against EDS for men alone. It is obvious that a ban on overtime work and a provision of mental health hygiene are the general strategies for reducing EDS at worksites. In the case of women, we suggest the formation of effective strategies for improving womens status at home and in the workplace must also be a solution for the prevention of EDS (e.g. promoting gender equality in the division of labor at home and strengthening family care policies for working women).

Night-Shift Work Related Problems in Young Female Nurses in Japan

Night‐Shift Work Related Problems in Young Female Nurses in Japan: Takashi Ohida, et al . Department of Public Health Administration, National Institute of Public Health—Background: The relationship of night‐shift work to sleep problems and work performance was examined in young female nurses in 11 hospitals in Japan. Methods: A cross sectional study was conducted by means of anonymous self‐administered questionnaires, carried out in July 1999. Subjects were 620 female nurses (Average age: 23.9) who started their careers in April 1997 and continued working in the same hospitals for two years and three months until the time of the survey. A questionnaire consisting mainly of items concerning sleep disorders from the Japanese version of the Pittsburgh Sleep Quality Index was distributed to the subjects. Results: Significant associations were observed between working on night shift and the use of alcoholic beverages to help induce sleep, and between working on night shift and daytime drowsiness. Significant differences were also observed between two and three‐shift systems with regard to subjective sleep quality. Moreover, average hours of sleep were significantly associated with three related sleep items: subjective sleep quality, difficulty in getting to sleep, and daytime drowsiness. Conclusion: Results suggest that in Japanese shift‐work systems, sufficient sleep hours are needed for nurses who work night shift to ensure good quality of sleep and consequently better services for patients.

Nightmare and sleep paralysis among Japanese adolescents: A nationwide representative survey

OBJECTIVE The objective of this study was to clarify the prevalence of nightmares and sleep paralysis and associated factors among Japanese adolescents. METHODS This study was designed as a cross-sectional sampling survey. The targets were junior and senior high schools throughout Japan. Self-reported anonymous questionnaires were sent to schools for all students to complete. RESULTS A total of 90,081 questionnaires were analyzed. The overall response rate was 62.6%, and the prevalence of nightmares and sleep paralysis was 35.2% and 8.3%, respectively. Multiple logistic analyses revealed that female sex, drinking alcohol, poor mental health, difficulty initiating sleep, low subjective sleep assessment, presence of excessive daytime sleepiness, and presence of sleep paralysis had higher odds ratios than others for nightmares. Male sex, poor mental health, drinking alcohol, taking a long daytime nap, early or late bedtime, difficulty initiating sleep, low subjective sleep assessment, presence of excessive daytime sleepiness, and presence of nightmares had higher odds ratios than other factors for sleep paralysis. CONCLUSIONS This study has revealed the prevalence of nightmares and sleep paralysis among Japanese adolescents. Furthermore, the results of this study suggest that it is important to maintain regular sleep habits for preventing these symptoms. We propose that health education about regular sleep habits should be promoted among Japanese adolescents.

Cigarette smoking among junior and senior high school students in Japan

PURPOSE To estimate the smoking prevalence among junior and senior high school students in Japan. METHODS We conducted a nationwide survey of adolescent smoking habits in 1990. Sample schools were selected by single random sampling. Self-administered anonymous questionnaires were sent to sample schools for all students to fill out. Seventy junior high schools and 33 senior high schools responded. A total of 57,189 students responded. RESULTS The current smoking rate (the proportion of students who had smoked at least once during the previous month) was much higher among boys than girls. The current smoking rate among seventh graders was 4.0% for boys and 1.5% for girls, and it increased with age to reach 25.5% for boys and 4.9% for girls in the twelfth grade. The percentage of regular smokers in the seventh grade was less than 1% for both sexes, but it increased to 20.3% for boys and 2.2% for girls in twelfth grade. Among current smokers, the proportion of boys smoking 1-9 cigarettes per day decreased, and the proportion of boys smoking 10 or more cigarettes per day increased, as age increased. Most current smokers buy their cigarettes from cigarette vending machines or tobacconist shops. CONCLUSIONS Since this survey reveals that smoking prevalence among students is not low even in junior high school, health education about smoking must start earlier and carry a greater emphasis within the curriculum. These results also indicate the importance of urging families to have greater concern for the smoking behavior of their children, of banning cigarette vending machines, and of preventing illegal sale of cigarettes to anyone under the age of 20 years.

Adolescent smoking behaviour and cigarette brand preference in Japan

Objectives: As part of efforts to develop a smoking control strategy for Japanese adolescents, the results of two nationwide surveys on adolescent smoking behaviour were compared. Design: Descriptive study on smoking behaviour among high school students was conducted. Self-reporting anonymous questionnaires were administered to 115 814 students in 1996 and 106 297 in 2000 through randomly sampled junior and senior high schools throughout Japan. Main outcome measures: Smoking prevalence, proportion of smokers by usual sources of cigarettes, national estimated cigarettes consumed by minors, share of cigarette brands smoked by high school students. Results: The experiment rate among junior high school boys decreased in 2000 compared with that in 1996, whereas current and daily smoking rates did not. Although prevalence among Japanese girls was much lower than that among boys, prevalence among girls increased in 2000. The main source of cigarettes among high school smokers was vending machines. The proportion of smokers who usually purchased cigarettes from vending machines increased in 2000, in spite of the 1998 introduction of restrictions on night-time operations. Japanese adolescents were more likely than adults to smoke American cigarette brands, and the adolescent market share of American brands has increased rapidly, especially for menthol brands. Conclusions: This survey revealed the seriousness of the problem of smoking behaviour among Japanese high school students, and suggested that this behaviour may be influenced by social environmental factors, including the marketing strategies of the tobacco industry. Action should be taken to reduce the prevalence and impact of pro-tobacco marketing messages and to abolish cigarette vending machines.