A interferência do ritmo biológico no rendimento escolar de pré-adolescentes de uma escola do Município de Esteio/RS

Os seres vivos convivem com processos rítmicos como as estações do ano, fases da lua e o ciclo dia e noite. Durante o período de 24 horas do dia, observa-se que há oscilações de temperatura corporal, freqüência cardíaca, pressão sanguínea, sono e vigília, etc., demonstrando que há uma organização temporal resultante dos relógios biológicos, os quais expressam o tempo interior ou endógeno da matéria viva com influências na vida cotidiana. Os ritmos biológicos são sincronizados com o ambiente e, se perturbados, podem comprometer o bom funcionamento do organismo. Assim como existem horários preferidos para dormir e acordar, a aprendizagem pode variar dependendo do horário do dia, conforme o ritmo biológico. De acordo com estas informações, foi realizada uma pesquisa com 202 alunos da 4ª série de uma escola de Ensino Fundamental, sendo 100 meninos e 102 meninas, com idades entre 10 e 12 anos, durante os anos de 2008 e 2009, referente ao ritmo biológico, ao desempenho escolar e às atividades realizadas fora da sala de aula, para obter informações relevantes sobre parâmetros que possam afetar o rendimento escolar. Foi utilizada a escala de Carskadon, que investiga os horários de sono e vigília de pré-adolescentes e adolescentes, bem como seus sentimentos em relação a estes horários. Esta escala classificou os alunos em vespertinos e matutinos. Foram feitas comparações entre o ritmo biológico, turno das aulas e rendimento escolar. Conforme análise estatística observou-se que, nos anos de 2008 e 2009 em conjunto, os alunos classificados como vespertinos que estudam no turno da tarde tiveram melhor rendimento escolar quando comparados com os matutinos em todas as disciplinas. Visando identificar qual ano contribuiu para esta significância, foram analisadas as correlações entre as três variáveis com alunos de 2008 e 2009 separadamente. No ano de 2008, constatou-se que não ocorreram diferenças significativas. No entanto, em 2009, entre os alunos do turno da tarde, os vespertinos tiveram um rendimento escolar superior ao dos matutinos. Conforme resultados da pesquisa referente às atividades realizadas fora da sala de aula, este grupo de alunos que está em casa pela parte da manhã, convivem menos com os amigos, fazem menos esportes, jogam mais jogos eletrônicos, se dedicam mais às tarefas escolares propostas para casa, apesar de lerem menos quando comparados com os matutinos. Com base nos resultados, conclui-se que os vespertinos que estudam no turno da tarde apresentam melhor rendimento escolar do que os matutinos que estudam no mesmo turno. Neste contexto, esta pesquisa busca obter e relacionar informações sobre o ritmo biológico e as atividades pessoais e sociais dos alunos de forma a contribuir para a descoberta do melhor momento da aprendizagem e também de um melhor rendimento escolar.All living beings coexist with rhythmic processes, like seasons, moon phases, the cycle of day and night. During the 24 hours of the day, fluctuations in body temperature, heart rate and blood pressure can be observed; and those variations demonstrate that there is some influence on quotidian life resulting from a temporal organization of biological clocks, which express the endogenous time of living matter. Biological rhythms are synchronized with the environment, and if disturbed, they can compromise the proper functioning of the body. Just as there are personal preferences for sleeping and waking, learning can vary depending on the time of day, according to biological rhythm. According to this information, we conducted a survey regarding the biological rhythm and outside activities of 202 students in the 4th grade of an elementary school (100 boys and 102 girls, aged between 10 and 12 years old, in 2008 and 2009), to get extra information on the subject about parameters that may affect school performance. We used the Carskadon scale, which investigates pre-adolescents’ and adolescents’ time of sleep and wakefulness, and how they feel about them. This scale classified students into matutinal and vespertine. Comparisons were made between biological rhythm, class shifts and school performance. Statistical analysis showed that in 2008 and 2009 combined, students classified as vespertine had better school performance when compared with the matutinal students group in all disciplines. In order to identify which year contributed to this significance, we analyzed the correlations between the three variables with students from 2008 and 2009 separately. In 2008, it was found that there were no significant differences. However, in 2009, the vespertine students in the afternoon shift had a better school performance than the matutinal group in the same shift. According to the results related to their extracurricular activities, students who are at home in the morning spend less time among friends, practice fewer sports, play more video games and are more dedicated to homework, though they read less when compared to matutinal students. Based on these results, we conclude that the verspertine students who study in the afternoon show better scholarly performance than matutinal students in the same period. In this context, this research aims to obtain and correlate information on biological rhythms and students’ personal and social activities to contribute to the discovery of the best time for learning and also better student performance

Effects of pacing modality on noninvasive assessment of heart rate dependency of indices of large artery function

Studies investigating the relationship between heart rate (HR) and arterial stiffness or wave reflections have commonly induced HR changes through in situ cardiac pacing. Although pacing produces consistent HR changes, hemodynamics can be different with different pacing modalities. Whether the differences affect the HR relationship with arterial stiffness or wave reflections is unknown. In the present study, 48 subjects [mean age, 78 ± 10 (SD), 9 women] with in situ cardiac pacemakers were paced at 60, 70, 80, 90, and 100 beats per min under atrial, atrioventricular, or ventricular pacing. At each paced HR, brachial cuff-based pulse wave analysis was used to determine central hemodynamic parameters, including ejection duration (ED) and augmentation index (AIx). Wave separation analysis was used to determine wave reflection magnitude (RM) and reflection index (RI). Arterial stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV). Pacing modality was found to have significant effects on the HR relationship with ED (P = 0.01), central aortic pulse pressure (P = 0.01), augmentation pressure (P < 0.0001), and magnitudes of both forward and reflected waves (P = 0.05 and P = 0.003, respectively), but not cfPWV (P = 0.57) or AIx (P = 0.38). However, at a fixed HR, significant differences in pulse pressure amplification (P < 0.001), AIx (P < 0.0001), RM (P = 0.03), and RI (P = 0.03) were observed with different pacing modalities. These results demonstrate that although the HR relationships with arterial stiffness and systolic loading as measured by cfPWV and AIx were unaffected by pacing modality, it should still be taken into account for studies in which mixed pacing modalities are present, in particular, for wave reflection studies.10 page(s

Cuffless Estimation of Blood Pressure:Importance of Variability in Blood Pressure Dependence of Arterial Stiffness Across Individuals and Measurement Sites

OBJECTIVE: Measuring arterial pulse transit time (PTT) to estimate blood pressure (BP) without conventional brachial cuff-based measurement is not new, but is a focus of current wearable technologies research. Much research pertains to efficient, accurate sensing of artery-related waveforms, yet the relationship between PTT and BP receives less attention despite being key for accurate BP estimation. This study investigated BP/PTT calibration by quantifying anatomical site variability (n = 10, 3 female, age 30 9 years) and individual variability ( n = 103, 50 female, age 53 22 years). METHODS: BP and pulse wave velocity (PWV) were measured in both seated and supine. Carotid-femoral PWV (cfPWV), carotid-radial PWV (crPWV), and carotid-finger-volume PWV (cvPWV) were measured with the wrist and hand positioned at the level of the upper thigh to achieve the same hydrostatic pressure effect across all measurements. RESULTS: The postural change invoked a small (4 7 mmHg) change in brachial diastolic BP with an additional 27 2 mmHg change in hydrostatic pressure. cfPWV decreased in the supine position (1.75 0.17 m s-1, p < 0.001), but crPWV and cvPWV were more variable. The calibration term (BP/PWV) across the sample population varied from 6.6 to 98.3 mmHg sm-1 (mean 22 14 mmHg sm-1) and was correlated with age, heart rate, diastolic and pulse pressure, and weight. These variables did not explain the majority of the variability (R2 = 0.248). CONCLUSION: There is anatomical site and between-individual variability in the calibration term for BP estimation from PTT. SIGNIFICANCE: Using and accurately calculating hydrostatic changes in BP within the individual may be one method to increase the accuracy of this calibration term

Heart rate dependency of large artery stiffness

Carotid-femoral pulse wave velocity (cfPWV) quantifies large artery stiffness, it is used in hemodynamic research and is considered a useful cardiovascular clinical marker. cfPWV is blood pressure (BP) dependent. Intrinsic heart rate (HR) dependency of cfPWV is unknown because increasing HR is commonly accompanied by increasing BP. This study aims to quantify cfPWV dependency on acute, sympathovagal-independent changes in HR, independent of BP. Individuals (n=52, age 40–93 years, 11 female) with in situ cardiac pacemakers or cardioverter defibrillators were paced at 60, 70, 80, 90, and 100 bpm. BP and cfPWV were measured at each HR. Both cfPWV (mean [95% CI], 0.31 [0.26–0.37] m/s per 10 bpm; P<0.001) and central aortic diastolic pressure (3.78 [3.40–4.17] mm Hg/10 bpm; P<0.001) increased with HR. The HR effect on cfPWV was isolated by correcting the BP effects by 3 different methods: (1) statistically, by a linear mixed model; (2) mathematically, using an exponential relationship between BP and cross-sectional lumen area; and (3) using measured BP dependency of cfPWV derived from changes in BP induced by orthostatic changes (seated and supine) in a subset of subjects (n=17). The BP-independent effects of HR on cfPWV were quantified as 0.20 [0.11–0.28] m/s per 10 bpm (P<0.001, method 1), 0.16 [0.11–0.22] m/s per 10 bpm (P<0.001, method 2), and 0.16 [0.11–0.21] m/s per 10 bpm (P<0.001, method 3). With a mean HR dependency in the range of 0.16 to 0.20 m/s per 10 bpm, cfPWV may be considered to have minimal physiologically relevant changes for small changes in HR, but larger differences in HR must be considered as contributing to significant differences in cfPWV.7 page(s

Effect of increasing heart rate on finger photoplethysmography fitness index (PPGF) in subjects with implanted cardiac pacemakers.

Finger photoplethysmography (PPG) is a noninvasive method that measures blood volume changes in the finger. The PPG fitness index (PPGF) has been proposed as an index of vascular risk and vascular aging. The objectives of the study were to determine the effects of heart rate (HR) on the PPGF and to determine whether PPGF is influenced by blood pressure (BP) changes. Twenty subjects (78±8 years, 3 female) with permanent cardiac pacemakers or cardioverter defibrillators were prospectively recruited. HR was changed by pacing, in a random order from 60 to 100 bpm and in 10 bpm increments. At each paced HR, the PPGF was derived from a finger photoplethysmogram. Cardiac output (CO), stroke volume (SV) and total peripheral resistance (TPR) were derived from the finger arterial pressure waveform. Brachial blood pressure (BP) was measured by the oscillometric method. This study found that as HR was increased from 60 to 100 bpm, brachial diastolic BP, brachial mean BP and CO were significantly increased (p<0.01), whilst the PPGF and SV were significantly decreased (p<0.001). The effects of HR on the PPGF were influenced by BP, with a decreasing HR effect on the PPGF that resulted from a higher BP. In conclusion, HR was a significant confounder for PPGF and it must be taken into account in analyses of PPGF, when there are large changes or differences in the HR. The magnitude of this effect was BP dependent

Effects of pacing modality on noninvasive assessment of heart rate dependency of indices of large artery function

Studies investigating the relationship between heart rate (HR) and arterial stiffness or wave reflections have commonly induced HR changes through in situ cardiac pacing. Although pacing produces consistent HR changes, hemodynamics can be different with different pacing modalities. Whether the differences affect the HR relationship with arterial stiffness or wave reflections is unknown. In the present study, 48 subjects [mean age, 78 ± 10 (SD), 9 women] with in situ cardiac pacemakers were paced at 60, 70, 80, 90, and 100 beats per min under atrial, atrioventricular, or ventricular pacing. At each paced HR, brachial cuff-based pulse wave analysis was used to determine central hemodynamic parameters, including ejection duration (ED) and augmentation index (AIx). Wave separation analysis was used to determine wave reflection magnitude (RM) and reflection index (RI). Arterial stiffness was assessed by carotid-femoral pulse wave velocity (cfPWV). Pacing modality was found to have significant effects on the HR relationship with ED (P = 0.01), central aortic pulse pressure (P = 0.01), augmentation pressure (P < 0.0001), and magnitudes of both forward and reflected waves (P = 0.05 and P = 0.003, respectively), but not cfPWV (P = 0.57) or AIx (P = 0.38). However, at a fixed HR, significant differences in pulse pressure amplification (P < 0.001), AIx (P < 0.0001), RM (P = 0.03), and RI (P = 0.03) were observed with different pacing modalities. These results demonstrate that although the HR relationships with arterial stiffness and systolic loading as measured by cfPWV and AIx were unaffected by pacing modality, it should still be taken into account for studies in which mixed pacing modalities are present, in particular, for wave reflection studies.10 page(s

Systolic time intervals assessed from analysis of the carotid pressure waveform

The timing of mechanical cardiac events is usually evaluated by conventional echocardiography as an index of cardiac systolic function and predictor of cardiovascular outcomes. We aimed to measure the systolic time intervals, namely the isovolumetric contraction time (ICT) and pre-ejection period (PEP), by arterial tonometry

Validação da escala de ritmo circadiano - ciclo vigília/sono para adolescentes Validación de la escala de ritmo circadiano - ciclo vigilia / sueño para adolescentes Validity of a circadian rhythm scale - sleep/wake cycle for adolescents

OBJETIVO: Validar a Escala Puberty and Phase Preference, de Carskadon, Vieira e Acebo (1993), traduzida para a língua portuguesa, que investiga os horários de acordar e dormir de adolescentes e seus sentimentos com relação a estes, denominando-os matutinos ou vespertinos. MÉTODOS: Participaram do estudo 144 alunos do ensino fundamental, 86 meninos e 58 meninas, com média de idade de 13,2±1,6 anos. A validade de constructo foi por critério preditivo. A escala de ritmo circadiano foi aplicada na sala de aula; após um mês de tal aplicação, os alunos foram solicitados a responder por sete dias consecutivos outro questionário. Este perguntava, referente ao dia anterior, o horário em que foi dormir e, referente ao próprio dia, o momento em que despertou. Para avaliar as evidências de validade de critério foram comparadas as médias por análise de variância one-way e teste post-hoc da diferença mínima significativa. RESULTADOS: As propriedades psicométricas da escala mostraram-se satisfatórias. A análise de consistência interna pelo alfa de Cronbach foi de 0,791. CONCLUSÕES: Os resultados indicaram fidedignidade e validade nas preferências de alocação do ciclo vigília e sono. Os índices foram significativos e direcionados aos horários esperados, evidenciando a validade da escala.<br>OBJETIVO: Validar la Escala Puberty and Phase Preference, de Carskadon, Vieira e Acebo (1993), traducida al portugués, que investiga los horarios de despertar y dormir de adolescentes y sus sentimientos respecto a esos horarios, nombrándolos matutinos o vespertinos. MÉTODOS: Participaron del estudio 144 alumnos de la primaria, 86 muchachos y 58 muchachas, con promedio de edad de 13,2±1,6 años. La validez de constructo fue por criterio predictivo. La escala de ritmo circadiano fue aplicada en el aula; después de un mes de esa aplicación, se solicitó que los alumnos contestaran, durante siete días consecutivos, a otro cuestionario. Éste preguntaba, referente al día anterior, el horario en que durmió y, referente al mismo día, el momento en que despertó. Para evaluación de las evidencias de validez de criterio, fueron realizados análisis de comparación de promedios con análisis de variancia one-way y prueba post-hoc de la diferencia mínima significativa. RESULTADOS: Las propiedades psicométricas de la escala se mostraron satisfactorias. El análisis de consistencia interna por el alpha de Cronbach fue de 0,791. CONCLUSIONES: Los resultados indicaron buena confiabilidad y validez en las preferencias de asignación del ciclo vigilia y sueño. Los índices fueron significativos y dirigidos a los horarios esperados, evidenciando la validez de la escala.<br>OBJECTIVE: To validate the Portuguese version of the Puberty and Phase Preference Scale, designed by Carskadon, Vieira and Acebo in 1993, which investigates the waking and sleeping time of adolescents and their feelings related to these habits, in order to classify them as morning or evening people. METHODS: The study included 144 elementary school students, 86 boys and 58 girls, aged 13.2±1.6 years-old. The construct was validated by a predictive criterion. The scale of the circadian rhythm was applied to the students in the classroom. One month later, for seven consecutive days, the students were asked to answer another questionnaire regarding the time they slept the day before and when they woke up on the next day. To evaluate the evidence of criterion validity, one-way variance analysis followed by the least significant difference post-hoc test were applied. RESULTS: The psychometric properties of the scale were satisfactory. The analysis of internal consistency by Cronbach's Alpha was 0.791. CONCLUSIONS: The results indicated good consistency and validity of the allocation preferences in the sleep/wake cycle. All indexes were significant and directed to the time expected, pointing out the scale validity