Chronotype ontogeny related to gender

Chronotype is an established concept designed to identify distinct phase relationships between the expression of circadian rhythms and external synchronizers in humans. Although it has been widely accepted that chronotype is subjected to ontogenetic modulation, there is no consensus on the interaction between age and gender. This study aimed to determine the relationship between age- and gender-related changes in the morningness-eveningness character in a large sample of people. A total of 14,650 volunteers were asked to complete the Brazilian version of the Horne and Östberg chronotype questionnaire. The data demonstrated that, on average, women were more morning-oriented than men until the age of 30 and there were no significant differences between men and women from 30 to 45 years of age. In contrast to the situation observed until the age of 30, women older than 45 years were more evening-oriented than men. These results suggest that the ontogenetic development of the circadian timekeeping system is more plastic in men, as represented by the larger amplitude of chronotype changes throughout their aging process. The phase delay of adolescence and phase advance of the elderly seem to be phenomena that are more markedly present in men than in women. Thus, our data, for the first time, provide support that sharply opposes the view that there is a single path toward morningness as a function of age, regardless of gender.

Anatomical study of the retroarticular process in dry human skulls

Introduction: The retroarticular process is a bony prominence formed by the thickening of the lateral borderof the mandibular fossa, forming the posterior wall of the temporomandibular joint. Since little is known anddiscussed about the retroarticular process, our aim was to study its presence, shape and size, relating thesefindings to the shape of the skulls according to the horizontal cephalic index.Materials and Methods:Weused 400 dry human skulls of the Institute of Science and Technology–UNESP Anatomy Laboratory. Eachskull was classified in brachycranics, mesocranics or dolichocranics, and then positioned on a craneostat tomeasure the height of the retroarticular process from its lower extremity to the auriculo-orbital plane. Thewidth was obtained by measuring the base of the process on its longer lateral axis.Results:The retroarticularprocess was found bilaterally in 397 skulls (99.25%). All the processes were classified into the following shapes:pyramidal (35.55%), tubercular (31.78%), mammilar (20.73%), crest-like (9.05%) and molar shape (2.89%);254 skulls (63.50%) showed the same type of process at the right and left sides (Kappa=0.496, moderateagreement). The average height and width were 5.28 mm and 12.81 mm, respectively.Conclusion:Theretroarticular process was found in almost all the skulls examined. There are no significant evidences aboutthe relationship among the presence, shape and size of the retroarticular process and the shape of the skullsaccording to the horizontal cephalic index. However, our findings led us to infer that there would be afunctional relationship between the process and the temporomandibular joint.

Influence of chronotype and social zeitgebers on sleep/wake patterns

Inter-individual differences in the phase of the endogenous circadian rhythms have been established. Individuals with early circadian phase are called morning types; those with late circadian phase are evening types. The Horne and Östberg Morningness-Eveningness Questionnaire (MEQ) is the most frequently used to assess individual chronotype. The distribution of MEQ scores is likely to be biased by several fact, ors, such as gender, age, genetic background, latitude, and social habits. The objective of the present study was to determine the effect of different social synchronizers on the sleep/wake cycle of persons with different chronotypes. Volunteers were selected from a total of 1232 UFPR undergraduate students who completed the MEQ. Thirty-two subjects completed the study, including 8 morning types, 8 evening types and 16 intermediate types. Sleep schedules were recorded by actigraphy for 1 week on two occasions: during the school term and during vacation. Sleep onset and offset times, sleep duration, and mid-sleep time for each chronotype group were compared by the Mann-Whitney U-test separately for school term and vacation. School term and vacation data were compared by the Wilcoxon matched-pair test. Morning types showed earlier sleep times and longer sleep duration compared with evening types (23:00 ± 44 and 508.9 ± 50.27 vs 01:08 ± 61.95 and 456.44 ± 59.08, for the weekdays during vacation). During vacation, the subjects showed later sleep times, except for the morning types, who did not exhibit differences for sleep onset times. The results support the idea that social schedules have an impact on the expression of circadian rhythmicity but this impact depends on the individual chronotype.

Influence of gender on psychomotor vigilance task performance by adolescents

During adolescence, the sleep phase delay associated with early school times increases daytime sleepiness and reduces psychomotor performance. Some studies have shown an effect of gender on psychomotor performance in adults and children. Males present faster reaction times (RT) compared with females. The aim of the present study was to evaluate the influence of gender on Palm psychomotor vigilance task (PVT) performance in adolescents. Thirty-four adolescents (19 girls, 13 to 16 years old) attending morning school classes of a public school in Curitiba, PR, Brazil, participated in the study. Sleep patterns were measured using actigraphy and sleepiness data were accessed with the Karolinska Sleepiness Scale (KSS). KSS and PVT measurements were collected at two times in the morning (8:00 and 11:00 h). The data were compared using one-way ANOVA, considering gender as a factor. ANOVA indicated that gender did not affect sleep patterns and subjective somnolence; however, a statistically significant effect of gender was detected for PVT performance. Boys presented faster RT (RT-PVT1: 345.51 ms, F = 6.08, P < 0.05; RT-PVT2: 343.30 ms, F = 6.35, P < 0.05) and fewer lapses (lapses-PVT1: 8.71, F = 4.45, P < 0.05; lapses-PVT2: 7.82, F = 7.06, P < 0.05) compared with girls (RT-PVT1: 402.96; RT-PVT2: 415.70; lapses-PVT1: 16.33; lapses-PVT2: 17.80). These results showed that this effect of gender, already reported in adults and children, is also observed in adolescents. The influence of gender should be taken into account in studies that use Palm PVT to evaluate psychomotor performance in this age range.

Becoming circadian: a one-year study of the development of the sleep-wake cycle in children

Data on three children's sleep-wake behavior during the first year of life submitted to spectral analysis reveal the presence of several frequencies in the circadian and ultradian ranges. The changes in the resulting spectra as age progresses show both an increase in overall rhythmicity, i.e., more data are explained by regular oscillations, and irregular changes in the circadian component. This circadian component shows an increase in power which appears at different ages among the individuals studied.