BACKGROUND AND OBJECTIVE: Sleep fragmentation (SF) is an important constituent of many sleep disorders. Sleep rebound following sleep disruption is regulated by homeostatic processes that also are influenced by stress and social isolation stress has not been studied in context of sleep disruption. We investigated interactions between social isolation and SF on sleep-wakefulness and delta EEG power during SWS in mice.
METHODS: C57/BLJ adult male mice were exposed to 6 h SF using a custom-designed apparatus that elicits minimal stress, along with telemetric polygraphic recordings for 24h. In paired or isolated mice, baseline recordings were followed by SF (every 2 min), for 6h.
RESULTS AND CONCLUSIONS: In contrast with other published methods that induce sleep disruption, SF procedures were void of increased serum corticosterone. SF in both paired and socially isolated mice elicited an increase in slow wave sleep (SWS) and REM, and a decrease in wake during the dark period. However, there was no change in total time (24 h) in wake or SWS in both the groups. SF also induced reduced sleep latencies following arousal. EEG delta power during SWS was significantly attenuated in isolated animals when compared to the paired group. Social interactions exert important effects on sleep structure and homeostasis, as evidenced by sleep latency and delta power of the EEG, the latter serving as a surrogate indicator of sleepiness. Social isolation may negatively affect the quality of sleep, even when total sleep time is unaffected, and experimental paradigms that induce sleep restriction should take into consideration the underlying effects of isolation on sleep.
Keywords: Sleep, Sleep fragmentation, Social isolation stress, Delta power, Sleep homeostasis, mice
BACKGROUND AND OBJECTIVE: Obstructive Sleep Apnea Syndrome (OSAS) is the most common sleep-disordered breathing (SDB) syndrome and is characterized by repetitive, total, or partial pharyngeal collapse during sleep. These symptoms induce both hypoxemia and brief arousals from sleep. As a result, daytime sleepiness, reduction in cognitive performance, an increase in the incidence of cardiovascular diseases and traffic accidents have been observed. To date, the most effective treatment for OSAS has been the use of Continuous Positive Airway Pressure (CPAP). Studies confirming the reversibility of alterations such as hypertension, hyperleptinemia, and an increase in inflammatory cytokines after therapy with CPAP in patients with OSAS are controversial. The purpose of this study was to evaluate the metabolic markers present in the blood of patients with OSAS before and after use of nasal CPAP treatment.
METHODS: Thirteen patients with moderate to severe OSAS were selected for the current study. After submitting their informed consent to participate in the study, the selected patients answered a sleep questionnaire and were submitted to a physical examination. They were also asked to perform a polysomnography throughout an entire night for diagnosis, CPAP pressure titration, and blood collection. All patients were submitted to treatment with CPAP for six months, after which all evaluations were repeated.
RESULTS: When we compared patients with OSAS with healthy control individuals, we found increased levels of ghrelin and triglycerides and reduced levels of HDL in patients with OSAS (p < 0.05). In addition, no difference in leptin levels was observed. After a six-month treatment period with CPAP, a significant drop in ghrelin levels could be observed (p < 0.05). No changes in the patients' body weight was observed during the treatment period (29±4 x 29±3 Kg/m2).
CONCLUSION: We thus concluded that OSAS can be considered an independent factor for increasing ghrelin levels and that a reduction in the levels of this hormone occurs after six months of CPAP treatment.
Keywords: Obstructive Sleep Apnea Syndrome, CPAP, leptin, ghrelin, obesity.
BACKGROUND AND OBJECTIVE: The aim of this study was to compare the effects of different paradoxical sleep deprivation methods on the pain threshold in rats submitted to inflammatory and neuropathic pain models. We also investigated whether changes in pain threshold could be reverted by sleep recovery period.
METHODS: Wistar rats were randomly assigned in arthritis-induced by adjuvant (AIA), chronic constrictive injury (CCI) of sciatic nerve and non-handled control group. Paradoxical sleep deprivation was performed using small or large platforms in the water tank technique. Grid and home-cage groups were also evaluated. Pain threshold was determined in dry environment using the hot plate test, before, during and after (recovery) paradoxical sleep deprivation.
RESULTS AND CONCLUSION: The data showed that AIA and CCI differ from control groups from the second day on after pain inducingprocedures and lasted until the third day of sleep recovery. Paradoxical sleep deprivation reduced the pain threshold in all groups studied, independently the method used. Sleep recovery did not restore the baseline pain threshold in arthritis-induced animals, but it was restored in CCI group submitted to both paradoxical sleep deprivation methods.
Keywords: sleep deprivation, pain, adjuvant-induced arthritis, sciatic nerve constriction, hot plate, rats.
BACKGROUND AND OBJECTIVE: The sleep of lactating rat dams were evaluated since informations on the subject are scanty.
METHODS: Electrographic recordings were made in nine rat dams, in different days after delivery (2nd to 20th day). Normal estrous cycling female rats, with previous motherhood experience, and four adult males were used as controls. Sleep-wakefulness was quantified and expressed as percentages of the total recording time and significance assessed by ANOVA, adopting significance level at the 0.05 level.
RESULTS: Total wakefulness was 43.4 ± 2.6% in control females, 44.3 ± 7.6% in the males and 55.1 ± 4.2% in LRD living with their 8 pups (difference rejected at the limit, p = 0.0547). The mean number of awakening episodes longer than 30 minutes was significantly greater in LRD. Synchronized wave sleep amounted to 46.6 ± 2.1%, 46.1 ± 7.6% and 41.9 ± 4.0%, respectively in control females, males and LRD. Desynchronized wave sleep (REM-sleep) was significantly reduced in LRD (3.0 ± 0.4%) compared to the values found in control females (10.0 ± 1.0%) and males (9.4 ± 0.6%). The average amounts of REM-sleep/hour along the recording period revealed to be constant and significantly lower in the lactating rat dams (3.0 ± 1.3%) comparatively to control females (11.6 ± 3.8%). An average of 1.2 ± 0.5 REM-sleep episodes/hour was also significantly lower in lactating females than in control females (3.2 ± 1.5).
CONCLUSION: The results suggest an adaptive reorganization of the sleep architecture in the female rat during the nursing period.
Keywords: sleep, nursing rats, lactation.
BACKGROUND AND OBJECTIVE: Good quality sleep and adequate amount of sleep are important in order to have better cognitive performance and avoid health problems and psychiatric disorders. Sleep-related disturbances affect a large percentage of university students and may cause impairments in their academic performance. Among the wide range of factors that can influence the sleep habits, university schedules are strongly related with sleep deprivation in students. This longitudinal study aims to investigate the effect of university schedules on medical students' sleep-wake cycle.
METHODS: We evaluated the Pittsburgh Sleep Quality Index (PSQI), a Sleep Habits Questionnaire and a sleep diary in three university semesters with different class starting times.
RESULTS AND CONCLUSION: The results demonstrated that when classes started earlier in the morning, the students had shorter sleep duration during weekdays, greater difference between weekday and weekend sleep duration (restriction-extension pattern) and worse sleep quality, showing the influence of class starting time on students' sleep habits.
Keywords: sleep habits, class starting time, sleep deprivation, sleep quality.
Although the number of published studies regarding the interaction between T1DM and the sleep-wake cycle is limited, the findings on the subject are nevertheless significant. Glycemic variation, as well as poor glycemic control, in T1DM seems to affect the sleep-wake cycle as a whole. Some important evidences available in the literature, comparing sleep in subjects with T1DM with control subjects, are: a trend towards increased total sleep time, decreased sleep latency, increased sleep efficiency, higher blood levels of growth hormone, epinephrine and ACTH throughout the night, and higher cortisol levels during the first half of the night. It is likely that not only the long-term consequences of hyperglycemia affect nocturnal sleep, but also the acute responses to hypoglycemia. In our view, the latter affects sleep in individuals with T1DM regardless of whether the hypoglycemic event occurred during the day or night. On the other hand, there are evidences that a poor night's sleep and sleep disorders may not only result in diurnal sleepiness, but could also worsen diabetes control, revealing a vicious circle. We suggest that improved glycemic control and avoidance of hypo- and hyperglycemia would minimize the impact of T1DM on circadian rhythms, lessening sleep disorders and improving both sleep duration and quality. At the same time, it would favor the maintenance of a good metabolic control.
Keywords: type 1 diabetes, glycemia, sleep, sleep-wake cycle, sleep quality.