Heart rate response to respiratory events with or without leg movements.

STUDY OBJECTIVE: This study compares the heart rate responses to the termination of respiratory events, both with and without associated leg movements. METHODS: Heart rate was measured for 15 R-R intervals before (T-15 to T-1) and after (T+1 to T+15) the termination of respiratory events as a change from the baseline rate, defined as the average of 10 R-R intervals occurring before the termination of each respiratory event (T-15 to T-6). Individual heart rate changes of the 21 patients were then averaged separately for 10 respiratory events with and 10 without associated leg movements. SETTING: N/A. PARTICIPANTS: Twenty-one patients with obstructive sleep apnea who had respiratory events both with and without associated leg movements. INTERVENTION: N/A. RESULTS: Maximal heart rate rise for respiratory events with leg movements (7.9 beats per minute) was significantly greater than for respiratory events without leg movements (5.1 beats per minute) (p < .0001). The area under the curve for heart rate increase from T-5 to T+9 was 50.1% higher for respiratory events with leg movements than without leg movements. When respiratory events with and without accompanying leg movements were compared, there were no significant differences in mean duration of respiratory events, mean oxygen desaturation after respiratory events, mean duration of electroencephalogram arousal following respiratory events, or mean heart rate during the baseline period. Heart rate rise did correlate with duration of the leg movements (p < .001) in those respiratory events with leg movements. CONCLUSIONS: Cardiac activation is significantly greater when the termination of respiratory events is associated with leg movements compared to those without leg movements. This exaggerated heart rate response may be an independent consequence of the leg movements themselves, as other features of the respiratory events and associated arousal were not different in the two conditions.

SCL-90-R and 16PF profiles of senior high school students with excessive internet use.

OBJECTIVE: To investigate the psychiatric symptomatology and personality characteristics of Korean senior high school students considered to use the Internet to excess. METHOD: We administered a questionnaire packet to students that included 4 measures. These measures included a questionnaire on Internet use patterns during the previous month, the Internet Addiction Test (IAT), the Symptom Checklist-90-R (SCL-90-R), and the Sixteen Personality Factor Questionnaire (16PF). A total of 328 students, aged 15 to 19 years, participated in the study. RESULTS: Students were divided into 4 Internet user groups according to their IAT total scores: nonusers (n = 59, 18.0%), minimal users (n = 155, 47.3%), moderate users (n = 98, 29.9%), and excessive users (n = 16, 4.9%). The SCL-90-R showed that the excessive users group, when compared with the other groups in this study, reported the highest levels of symptomatology. The 16PF also revealed that excessive users were easily affected by feeling, emotionally less stable, imaginative, absorbed in thought, self-sufficient, experimenting, and preferred their own decisions. CONCLUSIONS: This study suggests that senior high school students who use the Internet to excess report and subsequently exhibit significantly more psychiatric symptoms than students who use the Internet less frequently. In addition, excessive users appear to have a distinctive personality profile when compared with nonusers, minimal, and moderate users.

Age-related changes in sleep/wake patterns among Korean teenagers.

INTRODUCTION: As children go through the transition from childhood to adolescence, many shifts occur in sleep/wake patterns related to intrinsic and extrinsic developmental changes. These shifts have been shown to result in corresponding shifts in sleep phase (later sleep onset) and sleep deprivation among teenagers in Western societies. However, the effect of these developmental changes on the sleep habits of Korean teenagers has not been analyzed. This study aims to quantify age-related changes in sleep/wake patterns among Korean teenagers and elucidate cultural and other factors causing these changes. METHODS: The School Sleep Habits Survey was administered in homeroom classes to students in grades 5 to 12 (mean age: 13.7 +/- 2.4 years) selected via a 2-way stratification sampling method. The survey included items regarding usual sleep/wake patterns over the previous 2 weeks as well as measures of daytime sleepiness, sleep/wake-problem behavior, depressed mood, and morningness/eveningness. RESULTS: A total of 1457 students (52.9% male) completed the survey. The higher the grade, the later bedtime was found to be on both school days and weekends. There was a similar relationship between increasing grade and earlier wake time on school days, but higher grades were associated with later wake time on weekends. Total sleep time decreased by approximately 3 hours on school nights and 1 hour on weekend nights from grades 5 to 12. Adolescents were severely sleep deprived, with mean school-night total sleep times of 6.02, 5.62, and 4.86 hours for 10th-, 11th-, and 12th-graders, respectively. In the higher grades, there was a greater discrepancy between school nights and weekends in terms of bedtime and wake time, and the magnitude of weekend oversleep increased. Older students also reported more daytime sleepiness, more sleep/wake-problem behavior, more depressed mood, and more eveningness preference. The chief reasons students cited for their sleep deprivation differed across grades: Academic demands and entertainment (such as Internet and television) were reported by 5th- and 6th-graders, entertainment and then academic demands by 7th-, 8th-, and 9th-graders, and early school start time and academic demands by 10th-, 11th- and 12th-graders. CONCLUSIONS: This study clearly demonstrates that Korean adolescents do not get adequate sleep and that they have profound discrepancies in their sleep/wake patterns between school and weekend nights. Compared with previous studies from other countries, Korean students display even greater sleep deprivation and also more irregular sleep/wake patterns. This study also demonstrates that academic demands/stress and early school start time are the most important contributing factors for sleep deprivation among Korean adolescents. These findings stress the need to promote awareness of the magnitude of adolescent sleep deprivation and its detrimental effects in Korean society.

The influence of gender and upper airway resistance on the ventilatory response to arousal in obstructive sleep apnoea in humans.

The termination of obstructive respiratory events is typically associated with arousal from sleep. The ventilatory response to arousal may be an important determinant of subsequent respiratory stability/instability and therefore may be involved in perpetuating obstructive respiratory events. In healthy subjects arousal is associated with brief hyperventilation followed by more prolonged hypoventilation on return to sleep. This study was designed to assess whether elevated sleeping upper airway resistance (R(UA)) alters the ventilatory response to arousal and subsequent breathing on return to sleep in patients with obstructive sleep apnoea (OSA). Inspired minute ventilation (V(I)), R(UA) and end-tidal CO(2) pressure (P(ET,CO(2))) were measured in 22 patients (11 men, 11 women) with OSA (mean +/-s.e.m., apnoea-hypopnoea index (AHI) 48.9 +/- 5.9 events h(-1)) during non-rapid eye movement (NREM) sleep with low R(UA) (2.8 +/- 0.3 cmH(2)O l(-1) s; optimal continuous positive airway pressure (CPAP) = 11.3 +/- 0.7 cmH(2)O) and with elevated R(UA) (17.6 +/- 2.8 cmH(2)O l(-1) s; sub-optimal CPAP = 8.4 +/- 0.8 cmH(2)O). A single observer, unaware of respiratory data, identified spontaneous and tone-induced arousals of 3-15 s duration preceded and followed by stable NREM sleep. V(I) was compared between CPAP levels before and after spontaneous arousal in 16 subjects with tone-induced arousals in both conditions. During stable NREM sleep at sub-optimal CPAP, P(ET,CO(2)) was mildly elevated (43.5 +/- 0.8 versus 42.5 +/- 0.8 Torr). However, baseline V(I) (7.8 +/- 0.3 versus 8.0 +/- 0.3 l min(-1)) was unchanged between CPAP conditions. For the first three breaths following arousal, V(I) was higher for sub-optimal than optimal CPAP (first breath: 11.2 +/- 0.9 versus 9.3 +/- 0.6 l min(-1)). The magnitude of hypoventilation on return to sleep was not affected by the level of CPAP and both obstructive and central respiratory events were rare following arousal. Similar results occurred after tone-induced arousals which led to larger responses than spontaneous arousals. V(I) for the first breath following arousal under optimal CPAP was greater in men than women (11.0 +/- 0.4 versus 7.6 +/- 0.6 l min(-1)). These results demonstrate that the ventilatory response to arousal is influenced by pre-arousal airway resistance and gender. Whether this contributes to the perpetuation of respiratory events and the pathogenesis of OSA is unclear.

Cosleeping in young Korean children.

This study was an attempt to evaluate the present profile of parent-child cosleeping, to investigate the characteristics of those children who cosleep with their parents, and to determine the factors influencing cosleeping in Korea. Observed subjects consisted of 427 young Korean children aged 12 to 84 months. We used an interview method. The incidence of cosleeping was 377 (88.2%). Cosleeping decreased with increasing age. Cosleeping in Korean society was affected mostly by the age of parents and children, attitudes of the mother to cosleeping, and Korean traditional cultural values. The practice of cosleeping in young Korean children is very common and socially acceptable to Korean parents as a natural part of the child-rearing process. Korean family values and a cultural value system emphasizing familial bonds and interpersonal interdependence seems to act as positive reinforcing factors for the practice of cosleeping.