Physical activity and biological risk factors clustering in pediatric population
Introduction
Clustering of cardiovascular disease (CVD) risk factors is defined as the coexistence of several risk factors in the same subject [1]. In the literature, CVD risk factors are usually classified according to their nature: into biological (e.g., lipoproteins levels, blood pressure, body fatness, cardiopulmonary capacity, etc.) and behavioral or life style (daily physical activity, energy consumption, smoking, alcohol consumption, etc.) [1], [2], [3]. According to this classification, several studies have been carried out to determine the reciprocal risk factors influencing within the same nature and to observe the relation between risk factors of biological nature with life style risk factors and vice versa.
Although only one risk factor may contribute to CVD development, biological risk factors tend to cluster, being a potential effect for CVD development [1], [3], [4], [5], [6], [7], [8], [9]. A good example of risk factors clustering is the “metabolic syndrome”, which is characterized by the coexistence of abdominal obesity, hypertriglyceridemia, dyslipidemia, hypertension (HP), and hyperinsulinemia [10].
Berenson et al. [5] studied the influence of risk factors clustering in the extension of coronary and aortic atherosclerosis. In this study, several factors (body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), triglycerides, low density lipoproteins, and high density lipoproteins) were strongly associated with aorta artery and coronaries arteries injury extension. It was concluded that greater clustering of risk factors was associated with greater severity of aortic and coronary atherosclerosis. This conclusion reinforces the need to consider not only CVD risk factors in an isolated manner, but also in an associate manner [5].
In adult populations [11], [12], [13] as well as in pediatric populations [3], [8], [14], an investigation of the relationship between life style and biological risk factors has been conducted. Studies in pediatric populations have showed contradictory results in relation to the hypothetic influence of physical activity (PA) on biological risk factors clustering. Different methodologies in PA evaluation and different biological risk factors evaluated may be the reasons for the different results obtained in the studies related to this issue.
From a prevention point of view, it is especially important to investigate the life style risk factors connected to the clustering of CVD biological risk factors [3], [15]. Clearly, a primary prevention strategy for CVD is the change of life style risk factors, like increased PA, cessation of smoking, and the adoption of a healthy diet [2], [16], [17]. These changes are very important not only because life style risk factors are directly related to CVD, but also because they are indirectly related to biological risk factors like hypercholesterolemia, HP, and obesity [18].
To our knowledge, there are no studies in Portugal regarding the prevalence of biological risk factors clustering in pediatric population. Moreover, we have no knowledge of any study that investigates the relationship between life style risk factors and biological risk factors clustering. Therefore, the present study had two purposes: (I) to determine in children and adolescents of Porto area the coexistence of CVD risk factors (high blood pressure (HBP), percentage of high fat mass (%HFM), and high total cholesterol (HTC)) and (II) to study the relationship between PA and biological risk factors clustering (HBP, %HFM, and HTC).
Section snippets
Methodology
A total of 2157 children and adolescents were sampled, of whom 1533 (71%) and their parents agree to participate in the study. The sample for this study consisted of 699 males and 762 females aged 8–15 years. For each child or teacher not participating the form master was asked if the child differed from the rest of the class in any way. Six children, who had given consent to participate, chose on the day of testing not to take part because of problems with their skin. Five of the
Results
Partial correlations, adjusted for age in both sexes (Table 2), showed weak to moderate correlations among all the variables. The correlations between blood pressures and %FM were positive and significant, except for DBP in males.
Odds ratio and confidence intervals at 95% were used to analyze biological risk factors clustering Table 3, Table 4. Clustering between HBP and HTC was only significant in females, with an odds ratio of 1.6 (Table 3). It can also be observed that the highest odds ratio
Discussion
The underlying reasons for the selection of biological risk factors considered in this study (HBP, %HFM, and HTC) were the following: (I) they are recognized as some of the most important independent risk factors for CVD; (II) the insufficient knowledge of these risk factors clustering and their manifestation in pediatric years; and (III) they are considered important CVD predictors in adult life [14].
Regarding biological risk factors clustering and the relationship between life style risk
Conclusions
The results of the present study point toward biological risk factors clustering in children aged 8–15 years old, namely between HBP and %HFM in both sexes. The results also pointed out HBP and HTC clustering for females. Although the relationship was not significant, PA seemed to influence biological risk factors clustering, mainly in females. The results of the present study seem to suggest that children and adolescents with higher PAI have a lower number of biological risk factors for CVD.
Acknowledgements
This study was supported by the Foundation for Science and Technology, Program PRAXIS XXI: PSAU/122/96 and F.C.Gulbenkian 48988.
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