Quantifying entropy using recurrence matrix microstates.

We conceive a new recurrence quantifier for time series based on the concept of information entropy, in which the probabilities are associated with the presence of microstates defined on the recurrence matrix as small binary submatrices. The new methodology to compute the entropy of a time series has advantages compared to the traditional entropies defined in the literature, namely, a good correlation with the maximum Lyapunov exponent of the system and a weak dependence on the vicinity threshold parameter. Furthermore, the new method works adequately even for small segments of data, bringing consistent results for short and long time series. In a case where long time series are available, the new methodology can be employed to obtain high precision results since it does not demand large computational times related to the analysis of the entire time series or recurrence matrices, as is the case of other traditional entropy quantifiers. The method is applied to discrete and continuous systems.

Predictability of arousal in mouse slow wave sleep by accelerometer data.

Arousals can be roughly characterized by punctual intrusions of wakefulness into sleep. In a standard perspective, using human electroencephalography (EEG) data, arousals are associated to slow-wave rhythms and K-complex brain activity. The physiological mechanisms that give rise to arousals during sleep are not yet fully understood. Moreover, subtle body movement patterns, which may characterize arousals both in human and in animals, are usually not detectable by eye perception and are not in general present in sleep studies. In this paper, we focus attention on accelerometer records (AR) to characterize and predict arousal during slow wave sleep (SWS) stage of mice. Furthermore, we recorded the local field potentials (LFP) from the CA1 region in the hippocampus and paired with accelerometer data. The hippocampus signal was also used here to identify the SWS stage. We analyzed the AR dynamics of consecutive arousals using recurrence technique and the determinism (DET) quantifier. Recurrence is a fundamental property of dynamical systems, which can be exploited to characterize time series properties. The DET index evaluates how similar are the evolution of close trajectories: in this sense, it computes how accurate are predictions based on past trajectories. For all analyzed mice in this work, we observed, for the first time, the occurrence of a universal dynamic pattern a few seconds that precedes the arousals during SWS sleep stage based only on the AR signal. The predictability success of an arousal using DET from AR is nearly 90%, while similar analysis using LFP of hippocampus brain region reveal 88% of success. Noteworthy, our findings suggest an unique dynamical behavior pattern preceding an arousal of AR data during sleep. Thus, the employment of this technique applied to AR data may provide useful information about the dynamics of neuronal activities that control sleep-waking switch during SWS sleep period. We argue that the predictability of arousals observed through DET(AR) can be functionally explained by a respiratory-driven modification of neural states. Finally, we believe that the method associating AR data with other physiologic events such as neural rhythms can become an accurate, convenient and non-invasive way of studying the physiology and physiopathology of movement and respiratory processes during sleep.

[Probability of arterial hypertension from anthropometric measures in adults]. / Probabilidade de hipertensão arterial a partir de indicadores antropométricos em adultos.

OBJECTIVE: To associate anthropometric measures with arterial hypertension and develop a mathematical model to estimate this probability. SUBJECTS AND METHODS: A cross-sectional study was carried out with 3,445 adults of both sexes, between 18 and 60 years of age. Body mass index (BMI), waist-to-height ratio (WHR), waist circumference (HC), in addition age and sex were assessed. Blood pressure (BP) was measured and classified according to World Health Organization (WHO) and Brazilian Society of Hypertension (SBH) recommendations, using frequency analyses, correlation and logistic regression between variables, with p < 0.05. RESULTS: Males were twice as likely as woman to have hypertension, and for each year of life, the chance of hypertension increased 1.04 times. Odds ratio of hypertension in overweight individual increased two times, and in obese subjects, four times. CONCLUSION: Changes in body composition with advancing age, especially in men, were associated with hypertension, and assessment of these changes was relevant in the identification of this disease.

Probabilidade de hipertensão arterial a partir de indicadores antropométricos em adultos / Probability of arterial hypertension from anthropometric measures in adults

OBJETIVO: Associar medidas antropométricas com hipertensão arterial e desenvolver modelo matemático para estimar essa probabilidade. SUJEITOS E MÉTODOS: Estudo transversal com 3.445 adultos de ambos os sexos entre 18 e 60 anos. Avaliaram-se o índice de massa corporal (IMC), razão cintura estatura (RCE), perímetro da cintura (PC), além da idade e sexo. A pressão arterial foi avaliada e classificada segundo recomendações da Organização Mundial da Saúde (OMS) e da Sociedade Brasileira de Hipertensão (SBH). Utilizaram-se análise de frequência de casos, correlação e regressão logística entre as variáveis, com p < 0,05. RESULTADOS: Os homens apresentaram duas vezes mais chances de hipertensão que as mulheres, e, para cada ano de vida, essa chance aumenta em 1,04 vez. As chances de hipertensão dos considerados com sobrepeso foram de quase duas vezes e, nos obesos, quadriplicavam. CONCLUSÃO: Alterações da composição corporal com o avanço da idade, principalmente nos homens, associaram-se com hipertensão, sendo sua avaliação relevante na identificação dessa doença.

OBJECTIVE: To associate anthropometric measures with arterial hypertension and develop a mathematical model to estimate this probability. SUBJECTS AND METHODS: A cross-sectional study was carried out with 3,445 adults of both sexes, between 18 and 60 years of age. Body mass index (BMI), waist-to-height ratio (WHR), waist circumference (HC), in addition age and sex were assessed. Blood pressure (BP) was measured and classified according to World Health Organization (WHO) and Brazilian Society of Hypertension (SBH) recommendations, using frequency analyses, correlation and logistic regression between variables, with p < 0.05. RESULTS: Males were twice as likely as woman to have hypertension, and for each year of life, the chance of hypertension increased 1.04 times. Odds ratio of hypertension in overweight individual increased two times, and in obese subjects, four times. CONCLUSION: Changes in body composition with advancing age, especially in men, were associated with hypertension, and assessment of these changes was relevant in the identification of this disease.