br Materials and methods br Results Of

Materials and methods
Results Of the evaluated sample (N=1101), 533 subjects agreed to wear the actigraph. A total of 174 subjects were excluded due to problems such as incorrect device use, insufficient time of usage and technical problems. A final sample of 359 subjects was considered for the analyses. No differences in age (p=0.83) or in the proportion of males and females (p=0.08) were found among the sample of subjects who did not wear the actigraph (N=568), those who wore but were excluded (N=174), and the final sample (N=359). A significantly higher proportion of subjects from the upper socioeconomic class agreed to wear the actigraph (excluded and final sample) compared to the overall sample and the subjects who had not agreed (p=0.001). Of the 359 subjects, the age (mean±standard deviation) was 43±14 years, body mass index (BMI) was 26.7±5.7kg/m2, and 60% were female. The assessment of circadian preferences by MEQ showed a score of 58.0±10.7. The frequency of the subjects based on MEQ score is presented in Fig. 1 and shows a tendency toward morningness. The average number of days wearing the actigraph was 5.8±2.1 days (range 3–22.6 days). Actigraphic analyses showed that sodium butyrate the “main episode TST” was 365.4±57.4min and the “24h TST” was 371.6±58.1min, the sleep efficiency was 80.6±6.7%, the sleep latency was 12.5±11.0min, and WASO was 53.9±21.2min. Fig. 2 shows the dispersion of the subjects in the cluster analysis based on the actigraphic variables of time to sleep onset, sleep efficiency, sleep latency, and TST; these data characterized the distribution of the temporal sleep pattern in the subjects. A clear division along the horizontal axis was observed and was able to divide the subjects according to time to sleep onset: Group 1=morning type; Group 2=evening type; and Group 3=undefined type. The undefined type group appears to be representative of subjects with reduced sleep efficiency, almost independent of time to sleep onset. However, the highest score is below the reference line nearest the evening type group. Table 2 shows the demographics and actigraphic variables description of the study groups. The subjects in the evening type group (40.3±13.5 years) were younger than those in the morning type group (44.4±14.4 years) and the undefined type group (43.6±17.2 years). As expected, actigraphic variables were significantly different among the groups. Fig. 3 shows the distribution of the “main episode TST” and “24h TST” according to morning and evening types, both as defined by the actigraph variables. There was a trend of higher frequency of evening type among the subjects who had less than six hours of sleep compared to the morning type. The evaluation of the MEQ score according to the temporal pattern defined by the actigraph showed that the morning type group had higher scores than the evening type group (Fig. 4).
Discussion Other studies that evaluated a population-based sample [2] and a population of young adults [1] also showed that the average sleep duration and sleep efficiency were similar to our results (~6h and ~80%, respectively). It is important to note that habitual sleep duration among adults shows considerable variance within and between individuals [14], with a reported daily average of sleep of 6.8 hours [15]. However, some studies suggested that sleep duration as reported by North American adults decreased over the past 10 years [16]. Sleep efficiency was also decreased in our study, compared with the normal values found by polysomnograph (>85%). Considering that actigraph may systematically overestimated sleep efficiency when compared to polysomnograph [6] 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 [16–18].