Incidence of sexually transmitted diseases in Hokkaido, Japan, 1998 to 2001.

The objective of this study was to provide precise data on the incidence of sexually transmitted diseases (STDs) in Hokkaido. The goal of this prospective surveillance, study was to clarify the STD incidence between 1998 and 2001 in Hokkaido, Japan. The incidence of gonococcal infection in men was found to be 127-199 per 100000 people per year, which was three or four times higher than that for women. Female genital chlamydial infection had an incidence of 300-400 with a female to male ratio of two or three to one. Younger adults had higher incidences of gonococcal and chlamydial infections than older people. In conclusion, the current study of STDs revealed high incidences of gonococcal and chlamydial infections in the Hokkaido area, and there was no decreasing trend in STD incidence during these 4 years.

Clarification of the factor structure of the 12-item General Health Questionnaire among Japanese adolescents and associated sleep status.

If the factors affecting the mental health status of adolescents and their association with sleep status could be clarified, this information would be helpful for formulating lifestyle and healthcare guidance for the promotion of healthy growth and the prevention of mental problems in these individuals. The purpose of this study was to clarify (1) the factor structure of the 12-item General Health Questionnaire (GHQ-12), and (2) the associations between the factors extracted from this questionnaire and lifestyle, in particular sleep status, by using a representative sample population of Japanese adolescents. One hundred three thousand sixty hundred fifty self-administered questionnaires were collected from students enrolled in junior high and high schools in Japan. Of these questionnaires, 99,668 were analyzed. Sleep duration, subjective sleep assessment, bedtime, and insomnia symptoms of these students over the past month were studied to investigate sleep status. The factor analyses yielded two factors: depression/anxiety and loss of positive emotion. Sleep duration of less than 7h was found to be associated with both depression/anxiety and loss of positive emotion, whereas sleep duration of 8h or more was associated only with loss of positive emotion. Subjective sleep assessment and insomnia symptoms were associated with both depression/anxiety and loss of positive emotion. It was demonstrated that two underlying factors of mental health status were associated with differences in sleep status. In order to improve the mental health status of adolescents, it is important to provide guidance about sleep and lifestyle habits according to the mental health status of the individual.

Decrease in the prevalence of adolescent alcohol use and its possible causes in Japan: periodical nationwide cross-sectional surveys.

BACKGROUND: Trends in alcohol drinking prevalence were assessed among Japanese adolescents, and possible reasons for a decrease in drinking prevalence observed in 2004. METHODS: Cross-sectional nationwide surveys were conducted periodically. High schools were randomly sampled from throughout Japan in 1996, 2000, and 2004. All enrolled students in sampled schools were subjects of the surveys. Self-reporting anonymous questionnaires were collected from 115,814 students in 1996, 106,297 in 2000, and 102,451 in 2004. Questions about drinking prevalence of students and family members, proportion of students who have no friends, and sources of alcohol were included. Students who drunk at least one day of the 30 days preceding the survey were defined as the current drinkers. RESULTS: The drinking prevalence in 2004 was decreased in comparison to that in 1996 and 2000 in both sexes and in all school grades. The current drinking rate (monthly drinker) among junior high school boys was 29.4% in 1996, 29.0% in 2000, and 20.5% in 2004, while that among senior high school boys was 49.7%, 48.7%, and 36.2%, respectively. The respective prevalence among junior and senior girls was 24.0%, 25.5%, and 20.0% and 40.8%, 42.1%, and 34.1%. The prevalent sources of alcohol beverages were searching in home, stores (convenience store, supermarket, or gas-stand), liquor shops, and bars. An analysis of the reasons for this decrease identified a decrease in drinking prevalence in students' families, especially by fathers and older brothers, and an increase in the proportion of students who had no friends. CONCLUSIONS: A decrease in drinking prevalence of male family members and a limitation of sources of alcoholic beverages may contribute to the decrease in adolescent drinking prevalence.

[Decreases in Japanese adolescent drinking in 1996, 2000 and 2004 national surveys of Japanese junior and senior high school students].

We conducted three national surveys to clarify the drinking status of Japanese junior and senior high school students in 1996, 2000 and 2004. The total numbers of subjects in each survey were about 50 thousands junior high school students and 70 thousands senior high school students. The present study compares drinking status and alcohol related problems of the subjects of the three surveys. The results were as follows. First, drinking experiences of the subjects decreased over the three surveys. Those of junior high school students dropped from 60% to 40%, and those of senior high school students from 75% to 60%. Second, drinking behavior of the subjects has changed, e.g., the amount of drinking on each occasion has decreased, failures due to drunkenness have also decreased, compliance with the Law Prohibiting Minors Drinking has increased, their buying alcoholic drinks has decreased and experiences of being offered alcohol by parents have decreased. Third, male problem drinkers among the subjects decreased slightly but female problem drinkers did not decrease. We discussed the reasons why Japanese adolescent drinking has decreased. Over the past 10 years, Japanese society started to prohibit adolescent drinking, by revising the Law Prohibiting Minors Drinking, penalties for driving while intoxicated became more severe and Japanese alcohol consumption started to decrease.

Insomnia among Japanese adolescents: a nationwide representative survey.

STUDY OBJECTIVES: Although a number of previous studies have examined the prevalence of insomnia among adolescents, there have been very few nationwide studies. The objectives of this nationwide study were to clarify the prevalence of insomnia, its symptoms, and associated factors among Japanese adolescents. DESIGN AND SETTING: This study was designed as a cross-sectional sampling survey. The targets were 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 103,650 adolescents responded, and 102,451 questionnaires were subjected to analysis. INTERVENTION: N/A. MEASUREMENTS AND RESULTS: The prevalence of difficulty initiating sleep, difficulty maintaining sleep, and early morning awakening was 14.8%, 11.3%, and 5.5%, respectively. Insomnia was defined as the presence of one or more of these three symptoms. The prevalence of insomnia was 23.5%. Multivariate analyses revealed that, among junior high school students, male sex, poor mental health, skipping breakfast, drinking alcohol, smoking, not participating in extracurricular activities, and late bedtime had significantly higher odds ratios for insomnia. Among senior high school students, the same characteristics were associated with a significantly higher odds ratio for insomnia, as was the additional factor of having no intent to study at university. CONCLUSION: Insomnia in Japanese adolescents is common and associated with multiple factors. The results of this study suggest the need for comprehensive program to prevent insomnia in Japanese adolescents.

Unhealthy lifestyle, poor mental health, and its correlation among adolescents: a nationwide cross-sectional survey.

OBJECTIVES: The objective was to study the relationship between mental health and lifestyles of adolescents using samples representative of Japanese adolescents nationwide. METHOD: The survey was conducted between December 2004 and January 2005 among students enrolled in randomly selected junior and senior high schools. Self-administered questionnaires addressed lifestyles, sleeping habits, and mental health status. Of 103 650 questionnaires collected, 85 158 were analyzed. RESULTS: Population characteristics associated with poor mental health were being female, being a senior high school student, skipping breakfast, not participating in extracurricular activities, not consulting parents about personal matters, parental smoking, students' smoking or alcohol use, poor subjective sleep assessment, and short or long sleeping duration. CONCLUSION: Smoking and anxiety disorders are associated with an elevation in acculturative stress in adolescents. Prepossessing adolescents are in subclinical depression. Results suggest that lifestyles approaches in preventions that target students can be effective in reaching high-risk populations.

Cigarette smoking as a risk factor for stroke death in Japan: NIPPON DATA80.

BACKGROUND AND PURPOSE: Some previous Japanese cohort studies failed to show an association between smoking and stroke risk. Because such an association has been noted in other populations, this issue should be re-examined in a recent representative Japanese cohort with a higher total cholesterol level. METHODS: A total of 9638 men and women aged 30 years and older without a history of cardiovascular disease (CVD) at baseline in 1980 were followed-up for 14 years. RESULTS: We observed 203 stroke deaths (107 cerebral infarctions, 45 cerebral hemorrhages, and 51 others), 191 heart disease deaths, and 413 CVD deaths. The average serum total cholesterol level was approximately 4.91 mmol/L. Cox proportional hazard ratios were calculated adjusting for age, systolic blood pressure, and other conventional risk factors. The hazard ratios for men who smoked 1 to 20 cigarettes/day for all strokes, cerebral infarction, and cerebral hemorrhage were 1.60 (95% CI, 0.91 to 2.79), 2.97 (CI, 1.27 to 6.98), and 0.42 (CI, 0.16 to 1.09), respectively, and for those who smoked > or =21 cigarettes/day, they were 2.17 (CI, 1.09 to 4.30), 3.26 (CI, 1.11 to 9.56), and 0.68 (CI, 0.20 to 2.33), respectively. For women who smoked > or =21 cigarettes/day, the hazard ratio for all strokes was 3.91 (CI, 1.18 to 12.90). For CVD, all heart disease, and ischemic heart disease, the hazard risks of smoking were significant (1.49 to 4.25) for men but not significant for women. CONCLUSIONS: Smoking in a cohort with moderate serum total cholesterol level was a potent risk factor for stroke, especially cerebral infarction, for both men and women, and for CVD and ischemic heart disease for men.

Impact and correlates of poor sleep quality in Japanese white-collar employees.

STUDY OBJECTIVES: This study estimated the prevalence, examined associated impacts, and identified correlated factors of poor sleep quality among Japanese white-collar employees who were working in a labor market that included extensive downsizing and restructuring. DESIGN: A cross-sectional self-administered questionnaire survey was conducted as part of 2 consecutive studies on sleep. Sleep quality was measured with the Pittsburgh Sleep Quality Index. SETTING: A telecommunications company in the Tokyo metropolitan area. PARTICIPANTS: Of 5,924 workers, 5,090 responded (85.9%). Results from 4,868 daytime employees were analyzed. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The 1-month point prevalence of poor sleep quality was approximately 30% to 45% across age and gender and was significantly higher than in the general population of Japanese adults. The overall prevalence of absenteeism, poor physical and psychological health, problems in work performance and personal relationships, and accidents were 16.5%, 18.3%, 17.3%, 2.5%, 2.1%, and 1.8%, respectively. Poor sleepers were more likely to take sick leave, suffer from poor physical and psychological health, and have problems in occupational activities and personal relationships. The most strongly associated factor underlying poor sleep quality was perceived stress, followed by job dissatisfaction, being unmarried, poor bedroom environment, lower academic attainment, younger age, and hypertension. CONCLUSIONS: This study suggests that the cost related to poor sleep quality is extremely high. Comprehensive countermeasures against poor sleep quality at not only the individual, but also the organizational and societal levels, need to be considered for both employees and employers in order that health, safety, and productivity are ensured.

An epidemiologic study of self-reported sleep problems among Japanese adolescents.

STUDY OBJECTIVE: To examine the prevalence and correlates of sleep problems in Japanese adolescents. DESIGN AND SETTING: The survey was designed as a cross-sectional sampling. The targets of the survey were junior and senior high schools throughout Japan. Sample schools were selected by stratified cluster sampling. Self-reported anonymous questionnaires were sent to sample schools for all students to fill out. PARTICIPANTS: A total of 107,907 adolescents responded, and 106,297 questionnaires were subjected to analysis. MEASUREMENTS AND RESULTS: The overall prevalences of sleep problems in the month preceding the questionnaire were difficulty initiating sleep (boys: 15.3%, girls: 16.0%); nocturnal sleep duration less than 6 hours (boys: 28.7%, girls: 32.6%); excessive daytime sleepiness (boys: 33.3%, girls: 39.2%), and subjectively insufficient sleep (boys: 38.1%, girls: 39.0%). Multiple logistic regression analysis showed that female sex, being a senior high-school student, and having an unhealthy lifestyle (psychological stress, smoking, and drinking alcohol) were risk factors for sleep problems. CONCLUSION: Self-reported sleep problems in Japanese adolescents were common and were associated with multiple factors. There is a need for health education directed at solving sleep problems in Japanese adolescents.

Impact of elevated blood pressure on mortality from all causes, cardiovascular diseases, heart disease and stroke among Japanese: 14 year follow-up of randomly selected population from Japanese -- Nippon data 80.

The objectives of the study were to clarify the relationship between blood pressure and mortality from stroke, heart disease, cardiovascular diseases and all causes of death among representative population of Japanese and to estimate category-specific excess mortality from stroke due to blood pressure (BP) level. The study design comprised a retrospective cohort study using the 1980 National Survey on Cardiovascular Diseases and identification of underlying causes of death using national vital statistics data. In 1994, a 14-year follow-up cohort study was conducted among participants of the National Survey on Cardiovascular Diseases in 1980, randomly selected from the Japanese population. With a collaboration of 300 public health centres, which had conducted the original survey in 1980, 91.4% of the participants of the original survey could be followed up. Total observed person-years were 53948 for men and 70932 for women. During follow-up, 1327 deaths were observed. BP levels were significantly related to mortality from strokes, cardiovascular diseases and all causes of death for both sexes (P<0.001). Heart disease mortality was significantly related to BP levels among men (P<0.05) while not among women. Estimated excess mortality was 130% for men and 42% for women and chiefly observed among moderate hypertensives (48% for men and 16% for women). In conclusion, high blood pressure was a risk factor for mortality from all causes as well as those from cardiovascular diseases, stroke and heart disease among Japanese. Since the major part of excess mortality was due to mild hypertension, a population strategy to reduce blood pressure should be encouraged.

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 women's 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).

Seismic intensity and risk of cerebrovascular stroke: 1995 Hanshin-Awaji earthquake.

INTRODUCTION: No epidemiological data exist concerning the influence of an earthquake on the risk of stroke. Whether the incidence of cerebrovascular stroke increased after the 1995 Hanshin-Awaji earthquake (EQ) in Japan and whether seismic intensity affected stroke risk dose-dependently was examined. METHODS: A retrospective cohort study was conducted among residents, who were living in two towns on the island of Awaji and were participants of the National Health Insurance (NHI) program. The two towns were divided into 11 districts and their respective damage and socioeconomic states were investigated. Reviewing the NHI documents issued before and after the EQ, people who had strokes (9th International Classification of Diseases, codes 430-431 or 433-434.9) were identified. Risk of stroke in relation to the seismic intensities, was assessed with the Cox proportional hazard model. RESULTS: Among subjects aged 40 to 99 years, 45 of 8,758 (0.514%) had a stroke the year before the EQ 72 of 8,893 (0.810%) had a stroke in the first year following the EQ, and 49 of 8,710 (0.566%) had a stroke in the second year following the EQ. In districts where the earthquake's intensity was < or = 9.5 on the modified Mercalli intensity (MMI), compared with the year prior to the EQ, the relative risk (RR) of stroke was 2.4 (95% confidence interval (CI) = 1.1, 5.0) in the first year following the EQ, after adjusting for age, gender, and income. In that year, compared with MMI of < 8.5-9.0, RRs for 9.0-9.5 and > or = 9.5 were 1.6 (CI = 0.9, 2.1) and 2.0 (CI = 1.1, 3.7), respectively (p for trend 0.02). No trend for the RR was observed in the year before the EQ or in the second year following the EQ. CONCLUSION: The incidence of stroke increased in the first year following the EQ. The increase was associated with seismic intensity in a dose-response manner. Results suggest a potential threshold for RR of > or = 2.0 in areas near 9.5 on the MMI scale.

[An association (population attributable fraction) between smoking habit and mortality from all causes, cancer and lung cancer: NIPPON DATA80, 1980-1999. National Integrated Projects for Prospective Observation of Non-communicable Diseases and its Trend in the Aged].

OBJECTIVES: The authors examined the relationship and the population attributable fraction (PAF) between smoking habit and death from all causes, including cancer and lung cancer. METHODS: The baseline data were collected in the National Cardiovascular Survey in 1980 carried out for all household members aged 30 years or older in 300 districts, which were randomly selected throughout Japan. The number of participants in the survey was 10,546. The vital status was ascertained in 1999, and he calculated the adjusted relative risk of mortality and the PAF of mortality attributable to stopping smoking. RESULTS: A total of 9,629 subjects were available for the final analyses. There were 165,190 person-years of follow-up, and 2,011 deaths from all causes, including 579 deaths from cancer and 106 deaths from lung cancer. After adjustment for age and other cancer risk factors, smoking habit was associated with mortality from all causes, cancer and lung cancer. These associations had positive trends. The PAF (%) from all causes was 9.0 (male), 1.6 (female). The PAF (%) from cancer was 29.5 (male), 2.7 (female) and that from lung cancer was 42.9 (male), 7.1 (female). CONCLUSIONS: After adjustment for age and other cancer risk factors, smoking habit was associated with mortality from all causes, cancer and lung cancer. These associations had positive trends. The PAF (%) from all causes was 9.0 (male), 1.6 (female). The PAF (%) from cancer was 29.5 (male), 2.7 (female) and that from lung cancer was 42.9 (male), 7.1 (female).

[Study on factors for caries and infant feeding characteristics in children aged 1.5-3 years in a Kanto urban area].

PURPOSES: Generally, the incidence of caries in infants is decreasing, but the volume for children age 3 at Nakahara Ward in Kawasaki City is nearly 5 times higher than that of children at one year and 6 months of age (age 1.5). Here, we investigated the risk factors for cariogenesis during the period from age 1.5 till age 3, focusing on the household environment, lifestyle, diary habits and dental hygiene behavior. METHODS: A total of 491 children who had no caries at periodical health check at age 1.5 were chosen as subjects from those undergoing health check at our Public Health Center. The health check data at ages 1.5 and age 3 along with findings from the questionnaire survey at age 3 were analyzed by with reference to the presence or absence of caries in children at age 3. Odds ratios and 95% confidence intervals (CI95) were first estimated for each risk factor to identify those highly correlated to cariogenesis. Then, logistic regression analysis was performed after adjustment for mutual correlation among the factors. RESULTS: The risk factors significantly correlated to cariogenesis during ages 1.5-3 were maternal feeding at age 1.5 (Odds ratio: 2.80, CI95: 1.42-5.57) and sweet intake of sweets 3 times or more everyday at age 3 (Odds ratio: 2.07, CI95: 1.24-3.43). Moreover, the lack of nightly teethbrushing by parents appeared linked with cariogenesis, (Odds ratio: 1.68, CI95: 0.90-3.14), albeit without statistical significance. CONCLUSION: The present results indicate that caries is likely to be increased when maternal feeding is prolonged to age 1.5 and by consumption of sweets more than 3 times a day at age 3.

Adolescent smoking behavior in Japan, 1996.

We conducted second nationwide survey on smoking behavior among Japanese high school students. The survey was a cross-sectional sampling survey. The survey's targets were junior and senior high schools throughout Japan. Sample schools were selected by stratified cluster sampling. Self-administered anonymous questionnaires were sent to sample schools for all students to fill out. 65.6% of the junior high schools and 67.0% of the senior high schools were responded to this survey. A total of 117,325 students responded and 115,814 questionnaires were subjected to analysis. 7.5% of boys and 3.8% of girls in the 1st grade of junior high school were classified as current smokers, compared with 36.9% of boys and 15.6% of girls in 3rd grade of senior high school. Less than 1% of boys and girls in the 1st grade of junior high school were classified as daily smokers, this figure increased markedly by the 3rd grade of senior high school to reach 25.4% of boys and 7.1% of girls. Of students in the 3rd grade of senior high school, 21.2% of boys and 9.9% of girls had tried smoking before 13 year of age. Cigarette consumption also increased with age, although the proportion of those smoking 20 or more cigarettes per day did not. The major source for cigarettes among current smokers was vending machines. This survey revealed that smoking prevalence among Japanese high school students has already reached quite high level. Comprehensive energetic measures for control minor smoking are necessary in Japan.

[Japanese national survey of adolescent drinking behavior: comparison between 1996 and 2000 surveys].

This report shows Japanese adolescent drinking behavior from the national surveys conducted in 1996 and 2000. We randomly selected 120 junior high schools and 100 senior high schools nationwide. We requested the cooperation of the principals of these schools and sent questionnaires to each school. Students answered anonymously the questionnaires during school time, and sealed in envelopes by themselves; then teachers collected the envelopes. The questionnaire focused on adolescent drinking behavior. Valid responses numbered 42,798 (1996) and 47,246 (2000) from the junior high schools and 73,016 (1996) and 59,051 (2000) from the senior high schools. The number of students surveyed represented about 1% of all Japanese junior high school students, and about 2% of all senior high school students. This report covers only students who gave answers on both drinking frequency and drinking quantity. It compares adolescent drinking behavior between the 1996 and 2000 surveys, such as drinking frequency, drinking quantities, drinking occasions, methods of obtaining alcohol, kinds of alcohol drunk, alcohol-related problems, opinions on the law that prohibits minors under 20 years of age from drinking alcohol, and distribution of drinking status of the subjects by the Quantity-Frequency Scale (QF scale). In a comparison of adolescent drinking behavior between the 1996 survey and 2000 survey, non-drinkers among junior high school students increased from 45% to 55%, and those among senior high school students increased from 27% to 33%. On the other hand, ratios of female students in both junior and senior high schools who drank 1 or more times per week were higher in the 2000 survey than in the 1996 survey. Comparison of the 1996 survey and 2000 survey did not indicate that Japanese adolescent drinking has increased or decreased.

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.

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.