SoonJae Joo

Sleep habits, excessive daytime sleepiness and school performance in high school students

Abstract A questionnaire survey was carried out to examine the sleep habits and excessive daytime sleepiness (EDS) of 3871 high school students with a mean age of 16.8 years in Korea. The results showed that mean total sleep time was 6.3 h/day for male students and 6.5 h/day for female students, which may be insufficient for adolescence during puberty. The overall prevalence of EDS (defined as an Epworth sleepiness scale score of >10) was 15.9% (14.9% for boys and 18.2% for girls). The prevalence of EDS increased significantly (P < 0.001) with a decline in school performance.

Prevalence and correlates of excessive daytime sleepiness in high school students in Korea.

Abstract  The purpose of the present study was to determine the prevalence of excessive daytime sleepiness (EDS) and its associations with sleep habits, sleep problems, and school performance in high school students in South Korea. A total of 3871 students (2703 boys and 1168 girls with a mean age of 16.8 years and 16.9 years, respectively) aged 15–18 years in the 11th grade of high school completed a questionnaire that contained items about individual sociodemographic characteristics, sleep habits, and sleep‐related problems. The overall prevalence of EDS was 15.9% (14.9% for boys and 18.2% for girls). Mean reported total sleep time was similar in EDS and non‐EDS (6.4 ± 1.6 and 6.4 ± 1.3 h/day, respectively). The increased risk of EDS was related to perceived sleep insufficiency (P < 0.001), teeth grinding ≥ 4 days/week (P < 0.001), witnessed apnea ≥1–3 days/week (P < 0.01), nightmares ≥4 days/week (P < 0.05), low school performance (P < 0.01), and two or more insomnia symptoms (P < 0.05). Students with low school performance had a 60% excess in the odds of EDS compared to those whose school performance was high. These findings suggest that EDS is associated with multiple sleep‐related factors in adolescents. Whether interventions to modify associated correlates can alter EDS warrants consideration, especially because it may also improve academic performance in high school students.

Association of Snoring With Chronic Bronchitis

BACKGROUND Snoring is more prevalent in patients with chronic bronchitis than in persons without it. Few studies have examined the effect of snoring on chronic bronchitis. We prospectively investigated the association between snoring and the incidence of chronic bronchitis. METHODS The baseline study was conducted from June 25, 2001, to January 29, 2003. Members of the study cohort consisted of 5015 male and female Korean citizens aged 40 to 69 years at baseline who participated in a comprehensive health examination and on-site interviews at Korea University Ansan Hospital. Of these, 4270 participants (52% men and 48% women) entered the analysis for the first 2-year follow-up from April 17, 2003, to February 20, 2005, and those who met the same inclusion criteria remained in the analysis for a second 2-year follow-up period from February 21, 2005, to November 17, 2006. We collected information on snoring at baseline and identified incident cases of chronic bronchitis during a 4-year follow-up period. On the baseline questionnaire, we excluded participants who reported the presence of cough and sputum production on most days for at least 3 months a year. RESULTS During 4 years of follow-up, we documented 314 cases of new-onset chronic bronchitis (27.1 cases per 1000 person-years). After taking into account age, smoking, and other risk factors for chronic bronchitis, the multivariate relative risks of chronic bronchitis were 1.25 (95% confidence interval [CI], 0.95-1.64) for persons snoring 5 times per week or less and 1.68 (95% CI, 1.17-2.42) for those snoring 6 to 7 times per week compared with never snorers (P for trend = .049). The analyses stratified by risk factors, including smoking, occupation, and body mass index, showed a stronger association among never smokers, house workers, and overweight persons. In analysis for the joint effect of smoking and snoring, the relative risks of chronic bronchitis were 1.39 (95% CI, 1.01-1.90) for nonsmoking and snoring, 2.31 (95% CI, 1.38-3.87) for smoking and never snoring, and 2.86 (95% CI, 1.91-4.27) for smoking and snoring compared with nonsmoking and never snoring. CONCLUSIONS This prospective study observed that snoring is associated with chronic bronchitis. Our findings provide support for the hypothesis that snoring influences the development of chronic bronchitis.

Prevalence of excessive daytime sleepiness and associated factors in the adult population of Korea

OBJECTIVE Information on the prevalence and correlates of excessive daytime sleepiness (EDS) is limited for Asians. We determined the prevalence of EDS and its associated factors in the adult population of Korea. SUBJECTS AND METHODS The subjects consisted of 4405 Koreans aged 40-69 years from the Korean Genome Epidemiology Study, which is an ongoing prospective population-based study. Data were collected from a comprehensive health examination and a questionnaire at baseline. RESULTS The prevalence of EDS was 12.2% (10.7% for men and 13.7% for women). In multivariate models including sociodemographic, biochemical, clinical and sleep-related factors, age, physical activity, education, habitual snoring, waking up feeling unrefreshed, perceived insufficient sleep, and crawly feelings in the legs were significantly associated with EDS. Subjects aged 50-59 years had an excess risk of EDS by 1.42-fold (95% confidence interval [CI]=1.13-1.77) compared to those aged 40-49 years. In addition, the subjects with top quartile group of physical activity had a 1.80-fold (95% CI=1.18-2.73) higher risk of EDS than those with the lowest quartile group. A higher level of education was inversely associated with the risk of EDS. Furthermore, the subjects with habitual snoring had a 1.92-fold (95% CI=1.47-2.50) greater risk of EDS than non-snorers. Perceived insufficient sleep also increased the risk of EDS by 1.58-fold (95% CI=1.29-1.93) compared to perceived sufficient sleep. Subjects with crawly feelings in the legs had a 1.51-fold (95% CI=1.13-2.00) higher risk of EDS than those without crawly feelings in the legs. In addition, waking up feeling unrefreshed elevated a 1.24-fold (95% CI=1.01-1.53) risk of EDS compared to waking up feeling refreshed. CONCLUSIONS Our findings show that EDS is associated with a variety of factors in Korean adults, and habitual snoring or sleep-related problems increase the risk of EDS. Whether interventions to modify associated correlates can alter EDS warrants further study.

Habitual snoring is associated with elevated hemoglobin A1c levels in non-obese middle-aged adults

Hemoglobin A1c (HbA1c) is an indicator of long‐term glycemic control. The purpose of this study was to determine whether habitual snoring is associated with increased HbA1c levels in non‐obese and normoglycemic middle‐aged men and women. A total of 6981 subjects (3362 men and 3619 women) aged 40–69 years from the Korean Health and Genome Study were examined for the study. Each participant received a comprehensive physical examination as well as a set of questions pertaining to demographic characteristics and snoring frequency. Habitual snoring was defined as a snoring frequency of ≥4 days week−1. After adjusting for age, abdominal obesity, and other confounding covariates, male habitual snorers showed a 1.69‐fold excess [95% confidence interval (CI) 1.30–2.19] odds of having a high HbA1c level. Similarly, premenopausal women with habitual snoring had a 2.31 times (95% CI 1.22–4.39) significantly higher odds of having elevated HbA1clevels compared with non‐snorers. This association was not found in postmenopausal women. Multivariate analysis revealed that male habitual snorers aged 40–50 had a 2.08‐fold excess (95% CI 1.40–3.09) risk of having an elevated HbA1c level. In male habitual snores over 50, the strength of association was attenuated. Our findings based on cross‐sectional data support a hypothesis that habitual snoring is associated with impaired glucose tolerance even in non‐obese and normoglycemic men and premenopausal women. However, as waist circumference as an index of abdominal obesity (visceral adiposity) in the present study may only partially represent the effect of visceral fat, there may be a residual confounding from visceral obesity in our result. Longitudinal follow‐up studies are necessary to confirm the association between sleep‐disordered breathing and impaired glucose tolerance and to examine the causal relationship in a healthy population without obesity and diabetes.

Short-term incidence rate of hypertension in Korea middle-aged adults.

Objectives Despite recent increasing trends in cardiovascular morbidities and mortality in Asia, studies on short-term changes in cardiovascular risks remain limited. This study estimated 2-year incidence rates of hypertension in middle-aged Korean adults aged 40–69 years, and investigated the impact of baseline levels of blood pressure, body mass index, and other conventional risk factors on the progression to hypertension. Methods Blood pressures of participants were evaluated twice with a 2-year interval, measured by mercury sphygmomanometer according to the standardized protocol. Hypertension was defined when either the systolic and diastolic blood pressures were greater than 140 and 90 mmHg, respectively, or when a participant was treated with antihypertensive medications. Results The crude 2-year incidence (calculated per 100) of hypertension was 12.2; 13.0 for men and 11.6 for women. For those who had higher blood pressure at baseline examination, incidence rates were two-fold or five-fold higher compared with those with optimal blood pressure. Older age and overweight were also major predictors for hypertension, even in Koreans with a low serum cholesterol level. Conclusion This is the first investigation of short-term incidence rates of hypertension in Asia. The results are consistent with the recently reported increasing trends in cardiovascular mortality and morbidity in Asia.