"Considering that actigraph may systematically overestimated sleep efficiency when compared to polysomnograph  probably the sleep efficiency found in this study could be lower than 81%. There is considerable debate whether sleep duration decrease is resulting in higher rates of chronic sleep restriction or sleep debt and effects of sleep deprivation to the general population, including neurobehavioral and physiological (endocrine, immune and cardiovascular) consequences   . "
[Show abstract][Hide abstract] ABSTRACT: The aim of the present study was to characterize the temporal patterns of sleep and wakefulness in a sample of the adult subjects from São Paulo city. All subjects filled the Morningness/Eveningness Questionnaire (MEQ) and wore an actigraph for at least three consecutive days. A total of 359 subjects were considered for the analyses. The mean age was 43±14 years, the mean body mass index was 26.7±5.7 kg/m2, and 60% were female. The mean MEQ score was 58.0±10.7. The sleep pattern evaluated by the actigraphic analyses showed that 92% had a monophasic sleep pattern, 7% biphasic, and 1% polyphasic sleep pattern. Cluster analysis, based on time to sleep onset, sleep efficiency, sleep latency, and total sleep time, was able to identify three different groups denominated: morning type, evening type, and undefined type. Morning type subjects were more frequent, older, and had higher MEQ scores than evening type subjects. Our results showed that the actigraph objectively assessed the sleep-wake cycle and was able to discriminate between morning and evening type individuals. These findings suggest that the actigraph could be a valuable tool for assessing temporal sleep patterns, including the circadian preferences.
"Sleepiness is a transitional state between wakefulness and sleep that everybody can clearly perceive but nobody can reliably measure. Indeed, the physiological component of this subjective feeling has yet to be precisely defined in scientific terms, and the question of what might be a reliable physiological marker of sleepiness remains controversial (e.g., Dinges, 2004; Horne, 2004). Most recently, it was emphasized that, in spite of the extraordinary progress that has been made by circadian and sleep science in the last decades, the assessment of sleepiness is one of the remaining challenges (Czeisler, 2011; Mullington et al., 2011; Quan, 2011; Quan et al., 2011). "
[Show abstract][Hide abstract] ABSTRACT: Although circadian and sleep research has made extraordinary progress in the recent years, one remaining challenge is the objective quantification of sleepiness in individuals suffering from sleep deprivation, sleep restriction, and excessive somnolence. The major goal of the present study was to apply principal component analysis to the wake electroencephalographic (EEG) spectrum in order to establish an objective measure of sleepiness. The present analysis was led by the hypothesis that in sleep-deprived individuals, the time course of self-rated sleepiness correlates with the time course score on the 2nd principal component of the EEG spectrum. The resting EEG of 15 young subjects was recorded at 2-h intervals for 3250h. Principal component analysis was performed on the sets of 16 single-Hz log-transformed EEG powers (116Hz frequency range). The time course of self-perceived sleepiness correlated strongly with the time course of the 2nd principal component score, irrespective of derivation (frontal or occipital) and of analyzed section of the 7-min EEG record (2-min section with eyes open or any of the five 1-min sections with eyes closed). This result indicates the possibility of deriving an objective index of physiological sleepiness by applying principal component analysis to the wake EEG spectrum. (Author correspondence: [email protected]
Chronobiology International 04/2012; 29(4):509-22. DOI:10.3109/07420528.2012.667029 · 2.88 Impact Factor
"There is considerable debate as to whether or not sleep duration has been decreasing among adults in recent decades and if so, whether this reduction is resulting in higher rates of chronic sleep restriction or sleep debt (Dinges, 2004; Horne, 2004). However, according to the Center for Disease Control Morbidity and Mortality Weekly Report (2008), the percentage of adults who reported an average of less than or equal to 6 h of sleep within a 24-h period significantly increased from 1985 to 2004 (in both females and males and among all age groups 18–75). "
[Show abstract][Hide abstract] ABSTRACT: Sleep, which is evolutionarily conserved across species, is a biological imperative that cannot be ignored or replaced. However, the percentage of habitually sleep-restricted adults has increased in recent decades. Extended work hours and commutes, shift work schedules, and television viewing are particularly potent social factors that influence sleep duration. Chronic partial sleep restriction, a product of these social expediencies, leads to the accumulation of sleep debt over time and consequently increases sleep propensity, decreases alertness, and impairs critical aspects of cognitive functioning. Significant interindividual variability in the neurobehavioral responses to sleep restriction exists-this variability is stable and phenotypic-suggesting a genetic basis. Identifying vulnerability to sleep loss is essential as many adults cannot accurately judge their level of impairment in response to sleep restriction. Indeed, the consequences of impaired performance and the lack of insight due to sleep loss can be catastrophic. In order to cope with the effects of social expediencies on biological imperatives, identification of biological (including genetic) and behavioral markers of sleep loss vulnerability as well as development of technological approaches for fatigue management are critical.
Progress in brain research 01/2012; 199:377-98. DOI:10.1016/B978-0-444-59427-3.00021-6 · 5.10 Impact Factor
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