Revista Adolescência e Saúde

Revista Oficial do Núcleo de Estudos da Saúde do Adolescente / UERJ

NESA Publicação oficial
ISSN: 2177-5281 (Online)

Vol. 16 nº 1 - Jan/Mar - 2019

Original Article Imprimir 

Páginas 88 a 93


Analysis of the autonomic system of schoolchildren with and without a family history of systemic arterial hypertension

Análisis del sistema autonómico de escolares con y sin histórico familiar de hipertensión arterial sistémica

Análise do sistema autonômico de escolares com e sem histórico familiar de hipertensão arterial sistêmica

Autores: Emerson Branches de Sousa1; Luana Barbosa de Oliveira2; José Robertto Zaffalon Júnior3

1. Graduation in Physical Education by the University of the State of Pará (UEPA). 2nd Sergeant of the Military Police of the State of Pará. Professor of Military Physical Training (TFM) of the Institute of Security Education of Pará, Altamira, PA, Brazil
2. Graduation in Physical Education by the State University of Pará. Professor of Physical Education. Altamira, PA, Brazil
3. Graduation in Physical Education by the University of the State of Pará (UEPA). PhD in Rehabilitation Sciences. Professor at UEPA.Altamira, PA, Brazil

José Robertto Zaffalon Júnior
Av. Bom Jesus, nº 398 - Mutirão
Altamira, PA, Brasil. CEP: 68377-050
jrzaffalon@uepa.br

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Keywords: Adolescent; Autonomic Nervous System; Hypertension.
Palabra Clave: Adolescente; Sistema Nervioso Autónomo; Hipertensión.
Descritores: Adolescente; Sistema Nervoso Autônomo; Hipertensão.

Abstract:
OBJECTIVE: Analyze the autonomic system though (HRV) in students with and without positive family history of hypertension.
METHODS: Participated 243 schoolchildren of both sexesof sixth and seventh grase of public and private schools of the county of Altamira - Pará. 120 of them had hypertensive parents and 123 had normotensive parents. The cardiac autonomic modulation was assessed using the RR interval for a 7 minute period.
RESULTS: There also significant differences of the percentage values of low frequency band of the hypertensive's group when compared to the group of normotensive, and of the percentage values of high frequency in the group of normotensive when compared to the hypertensive.
CONCLUSION: It was possible to show that the hypertensive's had a higher sympathetic modulation and may be more likely to present cardiovascular diseases than the children of normotensive parents, who presented a higher parasympathetic modulation and consequently better HRV.

Resumen:
OBJETIVO: Analizar el sistema autonómico por medio de la VFC en escolares con y sin histórico familiar positivo de hipertensión arterial sistémica.
MÉTODOS: Participaron 243 escolares de ambos sexos del 6º y 7º año de las escuelas públicas y particulares del municipio de Altamira-Pará. De éstos, 120 tienen padres hipertensos (FH) y 123 tienen padres normotensos (FN). La modulación autonómica cardiaca fue evaluada utilizando el registro del intervalo R-R (ms) por el periodo de 7 minutos.
RESULTADOS: Hubo diferencias significativas de los valores porcentuales de la franja de baja frecuencia (%BF) en el grupo FH cuando se comparó al FN, y de los valores porcentuales de alta frecuencia (%AF) del grupo FN comparado al grupo FH.
CONCLUSIÓN: Fue posible dejar en evidencia que los FH presentaron mayor modulación simpática, pudiendo presentar mayor probabilidad de acometimiento de enfermedades cardiovasculares que los hijos de normotensos, los cuales presentaron mayor modulación parasimpática y consecuentemente mejor VFC.

Resumo:
OBJETIVO: Analisar o sistema autonômico por meio da VFC em escolares com e sem histórico familiar positivo de hipertensão arterial sistêmica.
MÉTODOS: Participaram 243 escolares de ambos os sexos do 6º e 7º ano das escolas públicas e particulares do município de Altamira-Pará. 120 destes têm pais hipertensos (FH) e 123 têm pais normotensos (FN). A modulação autonômica cardíaca foi avaliada utilizando o registro do intervalo R-R (ms) pelo período de 7 minutos.
RESULTADOS: Houve diferenças significativas dos valores percentuais da banda de baixa frequência (%BF) no grupo FH quando comparado ao FN, e dos valores percentuais de alta frequência (%AF) do grupo FN comparado ao grupo FH.
CONCLUSÃO: Foi possível evidenciar que os FH apresentaram maior modulação simpática, podendo apresentar maior probabilidade de acometimento de doenças cardiovasculares do que os filhos de normotensos, os quais apresentaram maior modulação parassimpática e consequentemente melhor VFC.

INTRODUCTION

The autonomic nervous system (ANS), also known as the visceral, automatic or vegetative nervous system, is part of the motor division of the peripheral nervous system and is directly related to the involuntary internal control and communication of the organism1.

The activity of the various organs, devices and systems that integrate the human organism are constantly influenced by the ANS that is indispensable for the maintenance of the conditions of the internal physiological balance, allowing it to perform the functions of interaction appropriately with the surrounding environment. If there is any imbalance, the organic and involuntary responses are immediate in order to reverse the ongoing process and reestablish the functional balance2. The ANS is fundamental for maintaining the body's balance, defined as homeostasis3.

These SNA functions influence the cardiovascular system, such as heart rate (HR), blood pressure (BP), peripheral vascular resistance and cardiac output. The SNA is divided mainly into two subsystems: the sympathetic nervous system (SNS) and the parasympathetic nervous system (SNP), functioning antagonistically, because while the NHS acts on the myocardium promoting the increase of the HR, the SNP acts on the sinoatrial node, atrial myocardium and the atrioventricular node, promoting its decrease4.

This oscillation in CF is called heart rate variability (HRV), and its analysis is based mathematically on the variation of time fired between consecutive heart beats. Changes in HRV patterns may point to possible health impairments in advance, and may be used to assess various clinical conditions involving the cardiovascular system5.

Reduction in HRV indicates an important factor for the appearance of cardiac events in apparently healthy individuals, in patients with heart disease, and also in hypertensive individuals5. In the case of hypertensive individuals, the HRV changes, indicating an increased sympathetic modulation6.

The hypertension in adolescents was only worrisome in the 60's and 70's, when several studies appeared, seeking to know the behavior of BP in this age group, its determinants and its relationships as heart disease in the future. Studies have also shown that systemic arterial hypertension (SAH) in parents has been shown to have important implications for the involvement of SAH in their children7.

In this sense, the HRV analysis may result in cardiovascular risk indicators, providing data on SNA behavior, since individuals with a positive family history of hypertension may present an increase in sympathetic activity to the detriment of the parasympathetic activity, which corresponds to a lower VFC8.9. This indicates that research involving methods for early diagnosis of the risk of hypertension, such as the evaluation of ANS through the analysis of HRV, is of fundamental importance, mainly among children and adolescents.


OBJECTIVE

To analyze the autonomic system through HRV in schoolchildren aged 11 to 14 years with and without a family history of hypertension.


METHODS

The present study is the result of a cross-sectional field study, which seeks to deepen the proposed questions even more than the distribution of population characteristics according to certain variables. Consequently, the planning of the field study presents greater flexibility, and it may be possible to reformulate its objectives throughout the research. This is an analytical study, since it involves a more detailed evaluation of data collection, with a quantitative and exploratory/descriptive objective10.

The study was carried out in 14 schools, 12 of which were municipal and 2 were private. The study included 243 students from the 6th and 7th grades, 11 to 14 years of age, of both sexes, divided into 120 children from hypertensive parents (FH) and 123 children of normotensive (FN). Subjects with a family history of dubious hypertension and/or individuals with diseases that could cause secondary systolic arterial hypertension were not included in the study.

Initially, a questionnaire with ten closed questions was applied, identifying the school's name, grade, class and age of the student, if one or both parents were hypertensive and medication was used to control BP, if one of their siblings or students had BP, if the student had already checked BP, ingested alcoholic beverages, smoked, practiced physical activity and intensity, so that it was possible to identify the participants with or without family history of hypertension.

BP was assessed in the resting condition after the student remained seated for approximately five minutes. An Aneroid Sphygmomanometer was used, with a specific cuff for children and adolescents.

The evaluation of the cardiac autonomic modulation was performed using the RR interval (ms) record for the seven-minute period, based on the Farah et al.6 study, with the participant at rest and supine position, using a Polar® model V800 cardio frequency meter . The log files were transferred to the Polar Flow Sync, which allows the bidirectional exchange of exercise data with a microcomputer for later analysis of cardiac pulse interval variability in different recorded situations.

After acquisition and storage of the data in the computer, the RR intervals from the cardio frequency meter were converted into Excel files to perform verification by visual inspection, which aimed to identify and/or correct some incorrect marking. The data were analyzed and tabulated through the CardioSeries program v.2.4 using the fast Fourier transform (FFT). After this analysis, absolute power was obtained in the respective pre-determined frequency bands: low frequency (BF = 0.04-0.15 Hz) and high frequency (AF = 0.15-0.4 Hz). The data were expressed in absolute values and in standard units. The BF component was used as an index of sympathetic activity, while the AF component was the index of parasympathetic activity.

According to Kawaguchi et al.11, this analysis can be done in two ways, in frequency and time domain. For the present study, the frequency domain was used.

The normality of the data was tested using the Shapiro-Wilk Test. The means were compared by analysis of variance (ANOVA). The results were presented as mean and standard error and the level of significance was set at p <0.05.

The project is registered in the Brazil Platform, and has met the specificities of resolution 466/12. All individuals participating in the research and their legal guardians signed the TALE and TCLE, respectively. The project is registered under CAAE # 55783416.2.0000.5168.


RESULTS

The results of the present study are presented in two tables. Table 1 presents the general information of the participants of the research, and Table 2 shows the characteristics of the evaluation of the autonomic modulation of the FN and FH.






The percentage values of the BF (% BF) of the FH group presented statistical difference (p = 0.028) compared to the values of the BF of the FN group, demonstrating that the FH have greater sympathetic modulation in relation to the FN.

In relation to the percentage values of the AF bands (% AF), the FN group presented a statistical difference (p = 0.028) compared to the FH group, thus demonstrating that the FN group presented higher parasympathetic modulation than the FH group. Thus, the FN group presented higher HRV than the FH group.


DISCUSSION

When identifying the subjects regarding the family historical factor, it is observed that 50.62% are children of normotensive (FN) (N = 123) and 49.38% of hypertensive children (FH) (N = 120). The mean age was 12.4 years in both groups. When analyzing data on systolic blood pressure, there was no statistically significant difference. However, there is a small difference between the mean values of NF equal to 104 (± 0.10) and those of the HF that presented higher blood pressure levels, equal to 105 (± 0.11).

There was also a small difference in relation to diastolic blood pressure, in which the mean values of pressure were 56 (± 0.08) between FN and 59 (± 0.09) FH.

Studies indicate that family history, such as obesity, sedentary lifestyle and environmental factors, indicate possible traits of SAH in individuals. In addition, they point out that children with BP measurement are more likely to become hypertensive adults12.

HE is one of the major challenges when it comes to public health, with a high prevalence especially among the younger population. This fact is worrying because the increase of BP levels in adolescence extends throughout life causing great complications in adulthood13.

Young people are prone to develop cardiovascular diseases, whether due to hereditary or environmental factors, and many are unaware of the main risk factors for their health, such as the adoption of inappropriate eating habits and physical inactivity, as well as alcohol abuse and smoking9.

The early identification of hypertension may have an important contribution to the implementation of health programs, through the implementation of healthy eating habits and the practice of physical exercises. This change in lifestyle can contribute positively to the reduction of cases of death due to hypertension or its complications, since physical exercises have been advocated as a tool to prevent numerous diseases6.

In their study, Magalhães et al.7 pointed out the relationship between physical activity and BP levels in adults and children. In this study, it was evidenced that children with physical fitness below the recommended level had higher BP levels at rest and during physical exertion. The study also points out that the best levels of physical conditioning accompany the decrease in pressure levels.

In this context, school physical education can act in the prevention of problems related to health, rehabilitation and various problems related to physical activities, since the National Curricular Parameters emphasize in their objectives that the physical education teacher can do with what the student knows and cares for his own body, values and adopts healthy habits as one of the aspects related to quality of life, acting responsibly in relation to his health and reproducing this learning the people of his family14. Physical school education is able to encourage the practice of physical exercise, contributing to the prevention/control of hypertension by maintaining blood pressure levels, and thus contributes so that the child and/or adolescent with a history of SAH in the family does not become a hypertensive adult.

In this perspective, the physical education teacher should always be concerned with developing his classes with the main objective of contributing to the overall development of the student, taking into account their motor and physiological aspects, encouraging care with the health and quality of life of the individual not only in the school context, but also outside of it.

Decreased HRV may be an important prognostic factor for cardiac events in previously healthy individuals, in which there is an increase in sympathetic modulation and a decrease in parasympathetic modulation6.

The HRV studies indicate a greater possibility of cardiovascular diseases in individuals with greater sympathetic modulation, and these diseases are the main causes of death and high public health expenditures5,8.

Although troubling, the decrease in HRV and its strong relationship with heart problems, especially with hypertension, studies report that physical exercise can provide significant benefits for the increase in HRV15. Physical exercise is able to produce beneficial effects to the body that can be used as prevention as well as initial treatment of hypertension, in which a single section of exercise of low or high intensity causes the reduction of BP, thus avoiding the use of medication and/or the reduction of their doses15,16.

It is well known that physical exercise is the most indicated in the prevention and control of hypertension and in the maintenance of pressure levels. Regular practice is able to make the child and/or adolescent with a history of high blood pressure in the family, do not become a hypertensive adult.

The discipline of physical education in this context is capable of promoting and encouraging the practice of regular physical exercise, and also intervene through contents that provide information and clarification on the importance of practicing physical exercise as well as the adoption of an active lifestyle and healthy.


CONCLUSION

Considering the results found, it was possible to show that the children of hypertensive patients presented greater sympathetic modulation, suggesting a greater probability of cardiovascular disease affection than the children of normotensive individuals, who presented greater parasympathetic modulation and consequently better HRV.

It is suggested that preventive health measures be implemented in schools so that children and adolescents of hypertensive parents reduce this risk factor. Among these preventive measures, we highlight the change in eating habits and especially the stimulation to practice physical exercises.


REFERENCES

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2. Paschoal M, Volanti V, Pires C, Fernandes F. Variabilidade da frequência cardíaca em diferentes faixas etárias. Revista Brasileira de Fisioterapia. 2006;10(4):413-419.

3. De Angelis K, Santos M, Irigoyen M. Sistema nervoso autônomo e doença cardiovascular. Revista da Sociedade de Cardiologia do Rio Grande do Sul. 2004;03.

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5. Gardim C, Oliveira B, Bernardo A, Gomes R, Pacagnelli F, Lorençoni R et al. Heart rate variability in children with type 1 diabetes mellitus. Revista Paulista de Pediatria. 2014;32(2):279-285.

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