Association of onset of obesity with sleep duration and shift work among Japanese adults.

OBJECTIVE: The objective of this longitudinal epidemiological study was to investigate the association of risk factors for cardiovascular illness with sleep duration and shift work. METHODS: This study used data obtained at medical checkups conducted in 1999 and 2006 for the employees of a local government organization in Japan (covering 21,693 male employees and 2109 female employees). The medical checkup data included (1) body measurements, (2) blood test parameters, and (3) replies to a self-administered questionnaire (inquiring about sleep duration, with or without shift work, etc.). On the basis of these data, we conducted multiple logistic regression analyses to study the association between the risk of new-onset obesity, hypertension, hyperglycemia, hypertriglyceridemia, and hypo-high density lipoprotein (HDL) cholesterolemia and shift work as well as sleep duration. RESULTS: Among the male subjects who were engaged in shift work, the relative risk of new-onset obesity for those with a sleep duration of less than 5 h was 1.30 (95% CI, 1.14-1.49) higher than for those with sleep duration of 5-7 h. Furthermore, analysis using both engagement in shift work and sleep duration as dependent variables showed that the relative risks of new-onset obesity for those with a sleep duration of less than 5 h were 1.20 (95% CI, 1.09-1.32) for men and 1.7 (95% CI, 1.11-2.87) for women. CONCLUSIONS: Short sleep duration is associated with onset of obesity.

Association between depression and insomnia subtypes: a longitudinal study on the elderly in Japan.

STUDY OBJECTIVE: To examine the association between depression and three subtypes of insomnia, namely, difficulty initiating sleep (DIS), early morning awakening (EMA), and difficulty maintaining sleep (DMS). DESIGN: Cross-sectional and longitudinal study. SETTING: Community dwellers in Japan. PARTICIPANTS: Nationally representative samples of adults aged 65 and over (total N=4,997) were selected by a multistage stratified random sampling method in 1999 and were interviewed face-to-face in 1999, 2001, 2003, and 2006. Those who responded to the 3rd survey conducted in 2003 and the 4th survey conducted in 2006 were used in this study. MEASUREMENT AND RESULTS: Depression was evaluated according to the 11-item short form of the CES-D scale at 2 points in time. Insomnia subtypes were assessed by self-reported measures. A logistic regression was employed to examine the association between insomnia subtypes and the presence of depression, controlling for relevant factors. A cross-sectional analysis based on the 2003 data demonstrated statistically significant odds ratios (ORs) for DIS and EMA. In the longitudinal study, DIS at the time of the 3rd survey was found to be significantly related to the presence of depression at the time of the 4th survey, with an odds ratio (95%CI) of 1.592 (1.012 to 2.504). EMA (OR 1.070; 95% CI, 0.664 to 1.723) and DMS (OR 1.215; 95% CI, 0.860 to 1.716), however, were not found to be significantly related to the presence of depression. CONCLUSION: The longitudinal study revealed a statistically significant relationship, controlling for other relevant factors, between DIS and the presence of depression three years later, but not between EMA or DMS and depression. Based on our findings, we recommend that the association between insomnia subtypes and depression be studied longitudinally in clinical settings.

Prevalence of and factors associated with smoking among Japanese medical students.

BACKGROUND: The aim of the present study was to determine the prevalence of and factors associated with smoking among Japanese medical students, to help promote effective antismoking measures in this population. METHODS: From the 80 university medical schools in Japan, 20 were randomly selected and invited to participate in our survey. The survey focused on medical students and employed an anonymous self-administered questionnaire. Information on each university's antismoking measures was obtained using a separate questionnaire administered to teaching staff. The survey was conducted from December 2006 through March 2007. Factors associated with smoking were identified by using the chi-square test and multiple logistic regression analysis. RESULTS: A total of 1619 valid surveys were returned. The overall prevalence of smoking was 13.7% (18.1% among men and 5.1% among women). Factors associated with smoking among medical students were male sex, enrollment at a private medical university, smoking by siblings, alcohol consumption, coffee consumption, insomnia, and less than 6 hours of sleep per night. CONCLUSIONS: Antismoking education must be further promoted to Japanese medical students, with consideration given to the factors associated with smoking behavior found in the present study.

Associations between sleep disturbance and mental health status: a longitudinal study of Japanese junior high school students.

BACKGROUND: A limited number of longitudinal studies have addressed the association between sleep disturbance and mental health status among adolescents. To examine whether each of these is a risk factor for the onset of the other, we conducted a prospective longitudinal study of Japanese adolescents. METHODS: In 2004, we performed a baseline study of students attending three private junior high schools in Tokyo, and in 2006, a follow-up study was performed on the same population. The mean age of the subjects was 13 years. The Pittsburgh Sleep Quality Index was used to evaluate sleep disturbance, and the 12-item General Health Questionnaire was used to evaluate mental health status. RESULTS: The subjects were 698 students, of whom 516 were suitable for analysis. The incidence of newly developed poor mental health status during the 2 years leading to the follow-up study was 35.1%. New onset of poor mental health status was significantly associated with new onset of sleep disturbance and lasting sleep disturbance. The incidence of sleep disturbance during the 2 years leading to the follow-up study was 33.3%. New onset of sleep disturbance was significantly associated with new onset of poor mental health status and lasting poor mental health status. CONCLUSIONS: Sleep disturbance and poor mental health status increase each other's onset risk.

A tale of two countries--the United States and Japan: are differences in health due to differences in overweight?

BACKGROUND: Despite similar standards of living and health care systems for older persons, there are marked differences in the relative health of the elderly populations in the United States (US) and Japan. We explore the association of overweight and obesity with these health disparities. METHODS: Data on older adults from the US National Health Interview Survey (1994) and the Longitudinal Study of Aging II (1994) were compared to similar data from the 1999-2001 Nihon University Japanese Longitudinal Study of Aging. Regression analyses for the 2 countries were conducted to examine the correlates of being overweight and obese, and the relationships of overweight and obesity with activities of daily living functioning, heart disease, arthritis, and diabetes. RESULTS: The prevalence of overweight and obesity is higher in the US than in Japan, as is the prevalence of heart disease, diabetes, arthritis, and functioning problems. Education level and marital status are predictors of overweight for older Americans but not for older Japanese people. Health behaviors affect weight in all groups. The prevalence of functioning problems and disease are more likely to be associated with being overweight in US men and women than in Japanese women, and are not associated with being overweight in Japanese men. CONCLUSION: Despite similar standards of living and health care systems for older persons, the conditions associated with poor health differ in the US and Japan. Being overweight or obese appears to be related to more functioning problems and arthritis in the US than in Japan.

Alcohol consumption behavior of pregnant women in Japan.

OBJECTIVE: This study was conducted to clarify the prevalence of alcohol consumption among pregnant women in Japan and its associated factors. METHOD: 344 institutions participated in the survey which was conducted in February 2006. Each subject was requested to fill out a self-administered anonymous questionnaire. Factors associated with alcohol consumption during pregnancy were examined using the chi-squared test and logistic regression analysis. RESULTS: The number of effective responses was 18,965. The prevalence of alcohol consumption before the confirmation of pregnancy and during pregnancy was 44.6% and 4.6% respectively. The following items were recognized as being associated with promoting alcohol consumption during pregnancy: greater number of weeks of pregnancy, more pregnancies, fewer years of schooling, being employed, an alcohol consumption before the confirmation of pregnancy, smoking during pregnancy, ignorance about the effects of alcohol consumption on fetuses, receiving advice regarding alcohol abstention, difficulty maintaining sleep, and daytime sleepiness. CONCLUSION: It is important to have a more comprehensive understanding of the factors associated with the alcohol consumption behavior of pregnant women, as revealed in the present study, in order to develop future policies for preventing alcohol consumption among pregnant women.

Alcohol consumption and abstention among pregnant Japanese women.

BACKGROUND: In order to clarify the alcohol consumption status of pregnant women in Japan and the characteristics of pregnant women who abstained from alcohol after their pregnancy had been confirmed, a nationwide questionnaire-based study of alcohol consumption behavior was performed. We also examined the factors associated with alcohol consumption during pregnancy and abstention after the confirmation of pregnancy. METHODS: After random sampling, 260 institutions participated in the survey; these were selected from a list of survey points fixed by the Japan Association of Obstetricians and Gynecologists. The study was conducted on pregnant women with confirmed pregnancies by using self-administered anonymous questionnaires during the period from February 1 through 14, 2002. RESULTS: Alcohol consumption during pregnancy was reported in 11.1% of the study participants, and abstention after the confirmation of pregnancy, in 76.9%. Significant associations were recognized between higher education and both alcohol consumption during pregnancy and abstention after pregnancy confirmation. Furthermore, alcohol consumption was significantly associated with parity, smoking, and shorter sleep duration, whereas abstention was significantly associated with less frequent alcohol consumption and knowledge regarding the risk of alcohol consumption. CONCLUSION: The results clarified the factors associated with alcohol consumption during pregnancy and abstention after the confirmation of pregnancy in Japan.

Smoking trends before, during, and after pregnancy among women and their spouses.

BACKGROUND: Pregnancy and childbirth can act as strong factors motivating parents to spontaneously quit smoking. The aim of the present survey was to establish smoking cessation guidelines for this group. The objectives were to clarify the smoking status of parents before, during and after pregnancy, as well as the factors associated with continuous smoking during pregnancy and post-partum smoking relapse among women who had stopped smoking during pregnancy. METHODS: A cross-sectional survey with self-administered questionnaires was conducted for the parents of the 908 infants who participated in the official medical and dental examination for 18-month-old infants in Itabashi ward, Tokyo, Japan. RESULTS: The prevalence of smoking among women before, during pregnancy, and at post-partum 18 months at 95% confidence intervals was 29.3% (23.3-35.3%), 9.8% (3.0-16.6%), and 23.1 (16.8%-29.4%), and among their spouses it was 64.3% (60.0-68.6%), 58.1% (53.4-62.7%), and 58.2% (53.5-62.8%), respectively. The positive factors associated with smoking among pregnant women were marriage to a smoker, less education, under stress, and part-time employment rather than unemployment. The positive factors associated with smoking relapse after childbirth among women were breast-feeding <6 months and age under 30 years. CONCLUSION: Compared with Western countries, the rate of smoking cessation during pregnancy was relatively high in Japan. It is necessary that smoking cessation intervention and support for men be initiated at the early stages of their spouses' pregnancies. These observations could influence the targeting and design of maternal smoking intervention.

Novel wide-range quantitative nested real-time PCR assay for Mycobacterium tuberculosis DNA: clinical application for diagnosis of tuberculous meningitis.

Although the "gold standard" for diagnosis of tuberculous meningitis (TBM) is bacterial isolation of Mycobacterium tuberculosis, there are still several complex issues. Recently, we developed an internally controlled novel wide-range quantitative nested real-time PCR (WR-QNRT-PCR) assay for M. tuberculosis DNA in order to rapidly diagnose TBM. For use as an internal control calibrator to measure the copy number of M. tuberculosis DNA, an original new-mutation plasmid (NM-plasmid) was developed. Due to the development of the NM-plasmid, the WR-QNRT-PCR assay demonstrated statistically significant accuracy over a wide detection range (1 to 10(5) copies). In clinical applications, the WR-QNRT-PCR assay revealed sufficiently high sensitivity (95.8%) and specificity (100%) for 24 clinically suspected TBM patients. In conditional logistic regression analysis, a copy number of M. tuberculosis DNA (per 1 ml of cerebrospinal fluid) of >8,000 was an independent risk factor for poor prognosis for TBM (i.e., death) (odds ratio, 16.142; 95% confidence interval, 1.191 to 218.79; P value, 0.0365). In addition, the copy numbers demonstrated by analysis of variance statistically significant alterations (P < 0.01) during the clinical treatment course for 10 suspected TBM patients. In simple regression analysis, the significant correlation (R(2) = 0.597; P < 0.0001) was demonstrated between copy number and clinical stage of TBM. We consider the WR-QNRT-PCR assay to be a useful and advanced assay technique for assessing the clinical treatment course of TBM.

Novel wide-range quantitative nested real-time PCR assay for Mycobacterium tuberculosis DNA: development and methodology.

Previously, we designed an internally controlled quantitative nested real-time (QNRT) PCR assay for Mycobacterium tuberculosis DNA in order to rapidly diagnose tuberculous meningitis. This technique combined the high sensitivity of nested PCR with the accurate quantification of real-time PCR. In this study, we attempted to improve the original QNRT-PCR assay and newly developed the wide-range QNRT-PCR (WR-QNRT-PCR) assay, which is more accurate and has a wider detection range. For use as an internal-control "calibrator" to measure the copy number of M. tuberculosis DNA, an original new-mutation plasmid (NM-plasmid) was developed. It had artificial random nucleotides in five regions annealing specific primers and probes. The NM-plasmid demonstrated statistically uniform amplifications (F = 1.086, P = 0.774) against a range (1 to 10(5)) of copy numbers of mimic M. tuberculosis DNA and was regarded as appropriate for use as a new internal control in the WR-QNRT-PSR assay. In addition, by the optimization of assay conditions in WR-QNRT-PCR, two-step amplification of target DNA was completely consistent with the standard curve of this assay. Due to the development of the NM-plasmid as the new internal control, significantly improved quantitative accuracy and a wider detection range were realized with the WR-QNRT-PCR assay. In the next study, we will try to use this novel assay method with actual clinical samples and examine its clinical usefulness.

Association between sleep duration and hemoglobin A1c level.

OBJECTIVE: The association between sleep habits and hemoglobin A1c (HbA1c) level has not been sufficiently examined. In the present study of residents in a local community, the associations between sleep duration and HbA1c level were examined. METHODS: Self-administered questionnaires were mailed to 1062 residents in a rural community in Japan, and completed questionnaires were collected. At the time of collection, the fasting plasma glucose and Hb(1c levels were measured using peripheral blood samples. For the analyses, values that were considered to represent high levels were a fasting plasma glucose level of 126mg/dl and a HbA1c level of 6.5%. Logistic regression analyses were performed to examine the associations between sleep duration and high fasting plasma glucose or high HbA1c levels. RESULTS: The prevalence of high fasting plasma glucose and high HbA1c levels was significantly high (p<0.01) in subjects with a short or a long sleep duration. Logistic regression analyses demonstrated a significant association between high HbA1c level and sleep duration. The adjusted odds ratios for a high HbA1c level showed high values with regard to both short and long sleep durations. CONCLUSIONS: HbA1c level showed a U-shaped association with sleep duration. These results suggest that there may be an appropriate range of sleep duration in individuals with glucose tolerance disorders. It is expected that the present findings will contribute to the treatment and prevention of diabetes mellitus.

Association between subjective well-being and sleep among the elderly in Japan.

OBJECTIVE: The purpose of this study was to examine the association between sleep and subjective quality of life in an elderly Japanese population. METHODS: Elderly people aged 70 years or more (n=1,769) were selected randomly from all areas of Japan. They were visited and interviewed in November 2003. Subjective well-being of the subjects was assessed using the Philadelphia Geriatric Center (PGC) Morale Scale. A logistic regression analysis was performed using sleep-related factors as explanatory variables. RESULTS: A positive linear association was observed between subjective sleep sufficiency and the mean PGC Morale Scale score. The crude and adjusted odds ratios for sleep disorders such as difficulty initiating sleep, excessive daytime sleepiness, and restless legs syndrome were significantly low. The mean score was highest for a sleep duration of 7-8h and became lower at sleep durations of <6 and 9h (inverted U-shaped association). However, the adjusted odds ratio for sleep duration did not show a significant reduction. CONCLUSIONS: In order to improve the subjective well-being of the elderly, better subjective sleep sufficiency and alleviation of sleep disorders are necessary. Different mechanisms may reduce subjective well-being in individuals who sleep less than 6h or who sleep 9h or more.

Effect of age at menopause on blood pressure in postmenopausal women.

BACKGROUND: A major mechanism of hypertension in many postmenopausal women is deficiency of female gonadal steroids. A long postmenopausal period may thus represent one factor that influences the prevalence of hypertension because of long periods of estrogen loss. METHODS: When we conducted a medical survey in northwestern China, we also asked 150 postmenopausal female subjects to provide age at menopause in a questionnaire. Age at menopause ranged from 37 to 57 years for all subjects. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) in all subjects were obtained from 24-h ambulatory blood-pressure monitoring. RESULTS: An inverse correlation was identified between age at menopause and SBP and DBP, and a positive correlation was found between postmenopausal period and either SBP or DBP. Blood pressure, age at menopause, and postmenopausal period were not significantly related to body mass index, plasma renin activity, glomerular filtration rate, or urinary excretion values of sodium and potassium. CONCLUSIONS: Our results clearly demonstrated that higher blood-pressure levels in postmenopausal women depend on age at menopause and postmenopausal period, but not subjects' age, suggesting that a longer absence of female gonadal steroids represents a major factor contributing to increased blood pressure in elderly women.

Use of alcohol and hypnotic medication as aids to sleep among the Japanese general population.

OBJECTIVE: The present study was conducted to clarify the prevalence of the use of alcohol and hypnotic medication as sleep aids, and associated factors, in the general population in Japan. METHODS: The survey was conducted in June 2000, using self-administered questionnaires, targeting a population that was selected randomly from among 300 communities throughout Japan. A total of 18,205 responses indicating alcohol use and 16,804 responses indicating hypnotic medication use were analyzed. RESULTS: The prevalence of alcohol use as a sleep aid one or more times per week was 48.3% among men and 18.3% among women. The prevalence of the use of hypnotic medication one or more times per week was 4.3% among men and 5.9% among women. The prevalence of alcohol used as a sleep aid increased gradually for men and women up to age 55-59 years and 40-44 years, respectively, and then declined with increasing age thereafter. The prevalence of the use of hypnotic medication among both men and women showed a trend toward a gradual increase with age. The use of alcohol as a sleep aid was associated with "difficulty maintaining sleep," but no such problem was associated with the use of hypnotic medication. CONCLUSIONS: Alcohol is a more popular sleep aid than hypnotic medication. The factors associated with the use of alcohol and of hypnotic medication are different.

Prevalence of smoking and associated factors among pregnant women in Japan.

OBJECTIVE: This study was conducted to estimate the prevalence of smoking among pregnant women living in Japan and to analyze the factors associated with their smoking behavior. METHOD: Five hundred institutions with maternity services were randomly sampled from a list of the Japan Association of Obstetricians and Gynecologists. Of these institutions, 260 participated in the survey which was conducted in February 2002. Using a self-reported anonymous questionnaire, a survey on smoking behavior, drinking behavior and sleep status was conducted on pregnant women. Chi-square tests and logistic regression analyses were used to examine the factors associated with their smoking behavior. RESULTS: Data were obtained from a total of 16,414 pregnant women. The prevalence of smoking during pregnancy was 9.9% [95% confidence interval (CI) 9.4%, 10.4%]. The quit rate of smoking among pregnant woman was 61.9% [95% CI 60.4%, 63.4%]. The odds ratios for smoking during pregnancy were significantly higher in women with relatively young age, less schooling, multiparous, exposure to passive smoking, short sleep duration and in women who drank. CONCLUSION: Smoking among pregnant women remains an important public health problem in Japan. It is necessary to promote antismoking measures based on the results of this study.

Quantitative nested real-time PCR assay for assessing the clinical course of tuberculous meningitis.

Although the "gold standard" for diagnosis of tuberculous meningitis (TBM) is bacterial isolation of Mycobacterium tuberculosis (M. Tb), there are still several complex issues. Recently, in the diagnosis of TBM, the detection of M. Tb DNA in cerebrospinal fluid (CSF) samples using PCR has been widely performed as more rapid, sensitive, and specific diagnostic method. Based on Taq Man(R) PCR, the authors developed a novel technique of internally controlled quantitative nested real-time (QNRT) PCR assay that provided a prominent improvement in detection sensitivity and quantification. Total 43 CSF samples from 8 serial patients with suspected TBM were analyzed. The CSF samples were collected before and during standard anti-tuberculosis treatments (ATT). The QNRT-PCR assay revealed positive results for 24 out of 43 serial CSF samples (55.8%) collected during the treatment course of ATT. Moreover, the bacterial cell (BC) numbers of M. Tb analyzed by the QNRT-PCR assay decreased gradually, correlating with the improvements of the patient's clinical conditions. Since the QNRT-PCR assay provides the ability to calculate a numerical value for the initial BC numbers of M. Tb in CSF samples, this method is an extremely useful and advanced technique for use in assessing the clinical course of TBM.

The relationship between depression and sleep disturbances: a Japanese nationwide general population survey.

OBJECTIVE: Among the existing epidemiologic studies that have examined the relationship between depression and sleep disturbances, there are few nationwide studies that have been conducted on subjects representing the general population. The present study was therefore conducted to clarify the relationship between depression and sleep disturbances, in particular the relationship between depression and both sleep duration and subjective sleep sufficiency, using a large sample representative of the general population. METHOD: The survey was conducted in June 2000, using self-administered questionnaires, targeting a population that was selected randomly from among 300 communities throughout Japan. Among the respondents, data from 24,686 individuals aged 20 years or older were analyzed. The Center for Epidemiologic Studies Depression Scale was used to assess the presence of depression. Sleep status, including sleep duration, subjective sleep sufficiency, and the presence or absence of insomnia symptoms, was evaluated. RESULTS: Those whose sleep duration was less than 6 hours and those whose sleep duration was 8 hours or more tended to be more depressed than those whose sleep duration was between 6 and 8 hours. Thus, sleep duration exhibited a U-shaped association with symptoms of depression. As subjective sleep sufficiency decreased, symptoms of depression increased, indicating a linear inverse-proportional relationship. CONCLUSION: The fact that sleep duration and subjective sleep sufficiency exhibited different relationships with symptoms of depression indicates that these 2 sleep parameters each have their own significance with regard to depression. These findings may be useful in the medical management of mental diseases.

Factors associated with exclusive breast-feeding in Japan: for activities to support child-rearing with breast-feeding.

BACKGROUND: Benefits of breast-feeding are not only limited to nutrition and sanitation in developing countries but also extend to cost-saving health care and alleviation of anxiety related to childrearing in developed countries. This study aims to elucidate factors associated with exclusive breast-feeding in Japan and use this information to achieve child-rearing support worldwide by promoting breast-feeding. METHODS: This cross-sectional study used data from a survey conducted by Ministry of Health, Labour and Welfare of the Japanese government, the First Longitudinal Survey of Babies in 21st Century. All subjects were infants (n=53,575) born in Japan in 2001 between January 10 and 17 and between July 10 and 17. According to the data, the exclusive breast-feeding rate in Japan during the first 6 months of life was 21.0%. We examined the factors associated with exclusive breast-feeding using univariate and multivariate logistic regression analyses. RESULTS: Among the factors examined, the adjusted odds ratio (OR) for exclusive breast-feeding was low for late childbearing, low birth weight infants, multiple births, smoking parents, living with grandparents, and feeling burdened by childrearing. The adjusted OR was high for factors that included sufficient childcare leave and consultation about childrearing with the spouse, a birth attendant and/or nurse, and a peer in a child-rearing circle. CONCLUSIONS: Exclusive breast-feeding is associated not only with medical factors but also with social factors. This study clarifies the necessity of social support to reduce the child rearing burden and a political system to promote paternal participation in childrearing and to improve the childcare leave system.

Epidemiological study on passive smoking among Japanese infants and smoking behavior of their respective parents: a nationwide cross-sectional survey.

BACKGROUND: Passive smoking is a well-known health hazard for infants. This study was conducted to: (1) estimate the prevalence of passive smoking among Japanese infants and (2) clarify the prevalence of indoor smoking and associating factors among parents having infants. METHODS: Subjects were all 53,575 infants born throughout Japan on January 10-17, 2001 or July 10-17, 2001. When the infants reached 6 months of age, the questionnaires were mailed to the homes. Family members answered questions that included information about the current smoking behavior of the parents. RESULTS: A total of 44,562 questionnaires (83.2%) were analyzed. The prevalence of smoking among the mothers and the fathers were 17.1% and 63.5%. The percentages of mothers and fathers who smoked indoors were 12.1% and 36.2%. The percentage of households where mothers and/or fathers smoked indoors was 37.5%. Multivariate logistic analysis indicated that young age, having a spouse who was a smoker, infants having many siblings, the mother not breast-feeding, and lower annual incomes had significantly higher odds ratios for both the mother's and the father's indoor smoking. CONCLUSIONS: Passive smoking is common among Japanese infants. To protect Japanese infants from passive smoking, further public health measures must be taken.

Daytime sleepiness, sleep habits and occupational accidents among hospital nurses.

AIM: This paper reports a study to determine the prevalence of excessive daytime sleepiness and sleep habits among hospital nurses and to analyse associations between excessive daytime sleepiness and different types of medical error. BACKGROUND: It has been reported that sleep disorders, and the tiredness and sleepiness brought about by sleep disorders may be associated with occupational accidents. However, to our knowledge, there has so far been no report on associations between sleep disorders, excessive daytime sleepiness in particular, and occupational accidents among hospital nurses. METHODS: The study was a cross-sectional study targeting 4407 nurses working in eight large general hospitals in Japan. An anonymous self-administered questionnaire was used to investigate their sleep patterns and experience of occupational accidents. The data were collected in 2003. RESULTS: The prevalence of excessive daytime sleepiness among hospital nurses in the present study was 26.0%. A statistically significant relationship was observed between having or not having occupational accidents during the past 12 months and excessive daytime sleepiness. Multiple logistic regression analyses on factors leading to occupational accidents during the past 12 months showed statistically significant associations between (1) drug administration errors and (2) shift work and age, between (1) incorrect operation of medical equipment and (2) excessive daytime sleepiness and age, and between needlestick injuries and age. CONCLUSIONS: Excessive daytime sleepiness is an important occupational health issue in hospital nurses. It is possible that occupational policies and health promotion measures, such as a provision of sleep hygiene advice and social support at worksites, would be effective in preventing occupational accidents among hospital nurses.