How do you measure cardiovascular health

Health and Fitness of German School Children

Summary

background

Overweight and lack of exercise pose a risk for cardiovascular diseases in children. The aim of the study was to record the cardiovascular health status and fitness of German primary and general school students as well as possible influencing factors.

methodology

In a prospective cross-sectional study, 357 children (9.6 ± 1.7 years) were examined for cardiovascular risk factors. The pulse wave velocity (PWV) as a measure of the arterial vascular elasticity and the bicycle ergometry for assessing fitness were determined.

Results

24% of the children were overweight (body mass index, BMI> 90th percentile) or obese (BMI> 97th percentile). Almost all of these children had visceral obesity (99%). In children with overweight / obesity, a lower vascular elasticity was more frequently detectable (PWV "standard deviation score", SDS 0.8 ± 1.0 vs. 0.2 ± 0.9 in children without overweight, p <0.001; PWV values> 95. Percentile 24% vs. 3%). The presence of overweight / obesity, primary school age, higher blood pressure and lower “high density lipoprotein” (HDL) cholesterol were independent predictors of lower vascular elasticity. In addition, children with overweight / obesity showed higher systolic blood pressure, a more adverse lipid metabolism profile, higher uric acid and glutamate pyruvate transaminase (GPT) values, as well as poorer physical fitness and higher media consumption. There was a significant association between BMI and glomerular filtration rate.

discussion

The cardiovascular risk associated with an increased BMI and reduced fitness is exacerbated by other risk factors for the development of a metabolic syndrome. In addition, there are indications that there are already structural changes in the vessels. Our data suggest a comprehensive assessment of the individual cardiovascular risk in overweight children and underscore the need to implement preventive measures early in children's daily lives in order to reduce cardiovascular morbidity in adulthood.

Abstract

Background

Obesity and a lack of exercise represent a risk for cardiovascular diseases in children. The goal of the study was to assess the cardiovascular health and physical fitness of German primary and secondary schoolchildren and to determine possible influencing factors.

Methods

In a prospective cross-sectional study 357 children (aged 9.6 ± 1.7 years) were investigated for cardiovascular risk factors. Pulse wave velocity (PWV) measurements were performed to assess arterial elasticity as well as ergometry and fitness tests.

Results

Of all children 24% were overweight (body mass index, BMI> 90th percentile) or obese (BMI> 97th percentile). Almost all these children suffered from visceral obesity (99%). Children with overweight / obesity more frequently showed a lower vascular elasticity (PWV standard deviation score, SDS 0.8 ± 1.0 vs. 0.2 ± 0.9 for children without overweight, p <0.001; PWV values> 95th percentile in 24% vs. 3%). The presence of overweight / obesity, primary school age, higher blood pressure and lower high-density lipoprotein cholesterol (HDL) were independent predictors for reduced arterial elasticity. Furthermore, overweight / obese children exhibited higher systolic blood pressure, a disadvantageous lipid profile, higher uric acid and alanine transaminase (ALT) values ​​as well as reduced physical fitness and higher media screen times. BMI was significantly associated with glomerular filtration rate.

Conclusion

The higher cardiovascular risk accompanying elevated BMI and reduced physical fitness is exacerbated by additional risk factors for the development of a metabolic syndrome. Furthermore, signs of structural changes of the vasculature can be detected. The data implicate a comprehensive assessment of the individual cardiovascular risk in overweight / obese children and underline the necessity for preventive measures to be implemented into the children’s daily routine early in life in order to reduce cardiovascular morbidity in adulthood.

Exercise and age-appropriate physical fitness are not only important prerequisites for adequate child development, but also decisive for the risk of later cardiovascular diseases. In view of the high rate of overweight and obesity and the increasing media consumption in childhood, the aim of this study is to examine the cardiovascular health of children and to determine the existing cardiovascular risk profile as a function of the body mass index (BMI).

introduction

Sufficient physical activity and age-appropriate physical performance are crucial for adequate child development. Deficits in this area can lead to increased morbidity in later life. However, children's physical activity and fitness are declining. In particular, increasing media consumption has a negative impact on the duration of sports activities and thus on the general health of children [1]. One consequence of this is the high frequency of overweight and obesity among children in Germany [2]. Overweight children show motor development retardation [3], with the difference to normal-weight peers increasing with increasing weight class [4]. Overweight children are very likely to be overweight in adulthood [5], which is associated with significantly higher mortality [6]. This increased mortality is particularly true for cardiovascular diseases, as these already originate in childhood in the form of cardiovascular risk factors and can lead to subclinical arteriosclerosis in childhood and adolescence [7]. The pulse wave velocity (PWV) as a measure of the vascular elasticity reflects structural changes in the larger arterial vessels. High measured values ​​indicate increased vascular stiffness and are therefore a marker for subclinical vascular damage. PWV is predictive of cardiovascular events and mortality in adults [8]. The oscillometric determination of the PWV has been validated for childhood. The low intra- and interobserver variability [9] as well as established age-specific norm values ​​for children [10] make it possible to diagnose subclinical changes in vascular elasticity non-invasively. In studies, obese children showed higher PWV values ​​[11, 12]. In addition to obesity, other classic cardiovascular risk factors (such as hypertension, dyslipidemia, diabetes) and chronic kidney failure can also lead to an increase in PWV [13, 14].

The results from the study on the health of children and adolescents in Germany (KiGGS) show that lower fitness and higher media consumption are associated with a lower socio-economic status of the parents [15]. A connection between a higher body mass index (BMI) and a lower socio-economic status as well as the existence of a migration background is also known [2, 16]. In the Obesity Patient Progress Documentation (APV) study, there was a clear increase in the frequency of screenings for comorbidities in overweight and obese patients, but this rate was significantly lower in patients with a migration background [17]. The subclinical vascular damage was not investigated in the two studies.

The aim of this study was to comprehensively examine the cardiovascular risk profile, physical fitness and performance as well as aortic vascular elasticity in school children, taking into account the existence of known influencing factors such as parental level of education (EBS) and migration background. For this purpose, as part of the introduction of a school exercise program, we assessed a year of 3 primary schools (2nd grade) and 2 comprehensive schools (5th grade) in Lower Saxony and North Rhine-Westphalia.

Methods

Subjects

205 children from the 2nd year of three primary schools and 152 students from the 5th year of two comprehensive schools were examined from April 2017 to June 2017. The study was approved by the ethics committee of the Hannover Medical School and carried out according to the principles of the Helsinki Declaration. The consent of the parents and children for the examinations was given.

Physical health

All participating children were examined by a pediatrician. Height, weight and waist circumference were measured and the BMI calculated. According to the guideline of the Working Group on Obesity in Childhood and Adolescence, children with a BMI> 90. – ≤97. Percentiles (pt.) Classified as overweight and with a BMI> 97. Pzt. as obese [18]; Visceral obesity was defined as a waist circumference> 97. Pzt. [18]. The blood pressure was measured in a standardized manner using an oscillometric measuring device validated for children (Dinamap v150; GE Medical Systems, Chicago, Illinois, USA) and using the cuffs provided for the respective arm circumference. After a ten-minute rest phase on the right arm in a sitting position, the measurement was carried out a total of three times and the average of the last two tests was used. The PWV was determined by two experienced examiners using a Vicorder (SMT Medical, Würzburg), as described above [10]. 78% of all children agreed to a blood test and 93% to a urine test. The analyzes were carried out in a central laboratory (Amedes, Hanover). The glomerular filtration rate (GFR) was calculated using the Schwartz formula [19]. In addition, a dental finding was collected, which included both the dental status and the assessment of the tooth supporting apparatus. Information on medical history, family anamnesis, extracurricular sport and weekly duration of media consumption (smartphone, television, computer, tablet) was obtained using the parents' questionnaire.

Physical performance and fitness

The maximum physical performance was determined by means of bicycle ergometry and given in watts / kg body weight (W / kg body weight) [20]. Coordination was tested by the number of side jumps over a line within 15 s, and the speed of action over the duration of a 20 m sprint. The degree of mobility was checked by bending the trunk forward. The children stand on a small platform and should guide their hands parallel to a centimeter scale in the direction of the toes with their knees straight. The maximum stretching position reached, which can be held for 2 s, is read off (touching the edge of the platform with your fingertips corresponds to 0 cm) [21].

Socio-economic factors

The EBS was divided into 3 categories according to the "International Standard of Classification of Education" [22]. If not a single parent, the highest value achieved by both parents was used. The EBS could be determined at 92%. Mutual migration background was defined if both parents or one parent and the child were born in another country; in the case of a one-sided migration background, only one parent or only the child has a different country of birth [23].

statistics

The data are given with mean and standard deviation or as number and percent. The measured values ​​were based on corresponding standard values ​​for height and weight [24], waist circumference [25], BMI [26] and PWV [10] according to gender and age, and blood pressure [24] according to gender, age and height in "standard deviation" score “(SDS) values ​​converted. An SDS value of 0 corresponds to the 50th item, 1.282 to the 90th item, 1.881 to the 97th item. [27]. The statistical calculations were carried out with SAS EG 7.1 (Statistical Analysis Software, Cary, North Carolina, USA). To check the normal distribution, we used the QQ plots of the individual variables and only found slight deviations from the normal distribution in individual cases, so that parametric tests were used. Continuous variables were tested using Pearson's correlation, categorical variables using χ2-Test or ANOVA. A p-Value <0.05 was considered significant. Independent influencing factors on the PWV were determined by means of multivariable linear regression with stepwise backward selection. Variables with p <0.2 in the univariate regression analysis were included in the multivariable model; the threshold for remaining in the model was on p <0.05 set.

Results

Study cohort

The characteristics of the study cohort are summarized in Tab. 1. The mean age of the children of the 2nd grade was 8.2 ± 0.5 years, of the children of the 5th grade 11.4 ± 0.6 years. The incidence of obese children was higher in the older children (17%) than in the younger children (8%). The waist circumference was increased in 40% in the sense of visceral obesity (2nd grade 37%, 5th grade 45%).

The mean systolic blood pressure in children of the 2nd grade was 102 ± 7 mm Hg (54th part) and the diastolic blood pressure was 60 ± 5 mm Hg (38th part). In children of the 5th grade, a mean of 106 ± 7 mm Hg (46th part) was measured for systolic values ​​and 62 ± 6 mm Hg (38th part) for diastolic values.

In bicycle ergometry, the younger children achieved an average of 3.1 ± 0.7 W / kgB as maximum output; the older ones got 3.0 ± 0.7 W / kgkg. Children in grade 2 completed an average of 23 ± 6 side jumps and needed 4.6 ± 0.5 s for the 20 m sprint.Children in grade 5 made 29 ± 7 side jumps and required 4.4 ± 0.4 s for the 20 m sprint.

59% of the younger and 38% of the older children participated in an after-school exercise such as B. Club sports. The use of electronic media averaged 10.5 ± 8.1 h / week in the younger children and 19.2 ± 14.0 h / week in the older children.

64% of the children had naturally healthy teeth. The remaining children had active carious lesions as well as teeth that had been conserved. In addition, 6% showed signs of local inflammation of the periodontium, such as deepened gingival pockets and bleeding when probing these pockets. Overall, 32% of the children in the 2nd grade and 20% of the children in the 5th grade needed dental treatment.

The EBS for the younger and older children was split between 36% and 20% of high, 40% and 50% medium and 24% and 30% low EBS. Among the younger children there was a bilateral migration background in 47% and a unilateral one in 13%, 49% of the older children had a bilateral and 10% a unilateral migration background.

Further information on the investigated cohort with regard to the investigated laboratory parameters can be found in Tab. 1. A comparison of the children with and without blood values ​​can be found in Table S1 (additional material online).

Pulse wave velocity

The PWV for children of the 2nd grade was 4.5 ± 0.4 m / s (66th pt.), For the children of the 5th grade it was 4.8 ± 0.4 m / s (58th pt. ) (Tab. 1). Elevated PWV values> 95 were found in 8% of all students. Pzt. (Fig. 1). The PWV was significantly higher in children with overweight than in children without overweight (Fig. 2).

The univariate analysis showed significant associations with blood pressure and anthropometric values, lipids and other blood parameters as well as maximum performance and media consumption (additional material online: Tab. S2). Influencing factors were sought using a multivariable linear regression analysis. Age, BMI classification, waist circumference SDS, diastolic blood pressure SDS, "high density lipoprotein" (HDL) cholesterol, "low density lipoprotein" (LDL) cholesterol, triglycerides, uric acid, glutamate pyruvate transaminase (GPT), GFR, highly sensitive C ‑ reactive protein, maximum performance, side jumps, 20 m sprint, EBS, migration status and media consumption were recorded as covariates. The multivariable analysis showed that younger age, higher diastolic blood pressure, lower HDL values, and overweight or obesity were associated with higher PWV (Table 2).

Overweight and obesity

Children who were overweight or obese (Tab. 3) were significantly more likely to have visceral obesity (p <0.001), showed higher systolic blood pressure (p <0.001), LDL- (p = 0.010), triglyceride (p <0.001), uric acid (p <0.001) and GPT values ​​(p <0.001) and lower HDL (p <0.001). The maximum physical performance was lower (p <0.001), and there was poor coordination (fewer side jumps, p <0.001) and slower action speed (slower in the 20 m sprint, p <0.001). The overweight or obese children were less likely to take part in sports after school (p <0.001) and showed greater media consumption (p = 0.004). In addition, there was a clear tendency for these children to have higher GFR values ​​(p = 0,058).

Migration background and socio-economic factors

Children with a one-sided migration background showed no significant differences to children without a migration background, so that these groups were combined and compared with children with a two-sided migration background. Children with a bilateral migration background showed a lower maximum productivity than children with a one-sided or no migration background (p <0.001; Additional material online: Tab. S3). The presence of a bilateral migration background had no influence on the BMI. Boys with a migration background showed higher levels of glucose (p = 0.039) and HbA1c-Values ​​(p = 0.043) and higher media consumption (p = 0.046); Girls with a migrant background were slower in the 20 m sprint (p = 0.026) and took part in sporting activity after school less often than children with a one-sided or without a migration background (p < 0,001).

Lower EBS was associated with higher BMI (p = 0.008; Tab. 4). Children with low EBS were also smaller (p = 0.004), showed a higher waist circumference (p = 0.014), lower max.performance (p <0.001), more media consumption (p <0.001) and a higher parental BMI (p = 0.002 or 0.041). There were no differences for blood pressure, PWV and the laboratory values.

discussion

Our data show a high proportion of overweight and obesity in elementary and comprehensive schools. These children showed lower vascular elasticity and physical fitness. Younger age, the existence of overweight or obesity, a higher diastolic blood pressure and lower HDL could be identified as independent predictors for a higher age- and gender-corrected PWV.

The PWV is a marker for the vascular elasticity and thus allows conclusions to be drawn about the extent of arteriosclerotic remodeling processes [28]. Overall, the PWV was 8% of all children over the 95th Pzt. and thus 3% higher than would be expected with a normal distribution. In these children, the aortic stiffness of the vessels is increased and can be classified as a subclinical incipient arteriosclerosis. In the group of children examined, overweight children showed significantly higher values ​​than children without overweight. The PWV of the children without overweight was on average at the 57th Pzt., For the overweight at the 72nd Pzt. and for the obese on average on the 86th Pzt. We were also able to identify the presence of overweight or obesity, higher blood pressure, younger age and lower HDL as independently associated factors for higher PWV. The importance of blood pressure, HDL or obesity on PWV has already been described in the literature [11,12,13,14, 29]. Due to the study design (investigation of 2 different age groups), the younger age corresponds most closely to the children of the 2nd grade, in whom a tendency to higher PWV can be seen compared to the children of the 5th grade (p = 0.078, Fig. 1). One possible explanation why elementary school children tend to have higher PWV is a higher vulnerability of the younger vascular system [13, 30].

Overweight and obesity were significantly more common in our cohort than the prevalences of wave 2 of the KiGGS study showed [2]. The difference was particularly large among the children in grade 5, who were on average 11 years of age, where the frequency of 17% was around twice as high as in the second KiGGS wave (6.5% for 11 to 13 year old girls or 8.0% for 11–13 year old boys) [2]. Not only the presence of overweight and obesity, based on the BMI, is associated with an increased cardiovascular risk, the abdominal fat distribution is also an important cardiovascular risk factor [31]. In the group we examined, almost all children (85 of 86) who were overweight also had visceral obesity (p < 0,001).

Overweight children also showed a number of other risk factors and initial indications of subclinical organ damage. These included higher blood pressure, a more disadvantageous lipid metabolism profile, higher uric acid and GPT values ​​and a tendency towards renal hyperfiltration. Although in most cases no pathological values ​​were detectable, the tendencies are clear and point to the strong predisposition of overweight children to develop a metabolic syndrome [32]. In addition, there were indications of existing organ damage. Overweight children showed significantly less vascular elasticity (PWV values> 95 pzt. In 24% vs. in 3% of the children without overweight, p <0.001), which can be interpreted as existing subclinical vascular damage. In agreement with the literature describing hyperfiltration as a consequence of obesity-associated glomerulopathy [33], we also found a significant correlation between BMI and GFR. The significantly higher GPT values ​​in overweight children can also indicate involvement of the liver in the sense of a “non-alcoholic fatty liver disease” (NAFLD), which is the hepatic manifestation of the metabolic syndrome [34].

Against the background of the relationships between overweight and obesity for cardiovascular risk, it seems important to emphasize that in our cohort - in accordance with the results of the KiGGS study [2] - children with low EBS had higher BMI values. In addition, we were able to show that these children took part in extracurricular sporting activities less often, displayed more media consumption and showed a lower maximum performance. In contrast to the EBS, we did not find any evidence of more overweight in children with a bilateral migration background, but a lower maximum performance. In addition, there were gender-specific differences in this group (girls participated less often in extracurricular sporting activities, boys showed significantly higher media consumption), which were not detectable in children with no or one-sided migration background. While children with low or medium EBS represent a clear risk group that requires special attention, individual prevention strategies seem particularly useful for children with a bilateral migration background.

The strength of our study is the comprehensive examination of a large cohort of German school children, in which a large number of cardiovascular risk factors as well as parameters for physical fitness and performance were determined. The limitations of the study include the "cross-sectional" study design and the numerous, albeit statistically corrected, comparisons. Blood withdrawals were also not feasible from all children, but the rate of 78% for voluntary blood withdrawal was gratifyingly high. The comparison of the children with and without blood values ​​showed no significant differences, so that a bias is not likely.

Summary

The pathogenesis of cardiovascular morbidity begins in childhood [7], so the prevention of cardiovascular mortality in adults must begin in childhood. In this prospective observational study on 357 school children, we were able to show that children with overweight / obesity (BMI> 90. Pzt.) Not only have a clear risk profile for the development of cardiovascular morbidity in later life, but also show evidence of subclinical organ damage in childhood.

The PWV in childhood has been validated as a marker for arterial vascular elasticity [8] and can also be measured easily and non-invasively [9]. Although the predictive value of PWV for cardiovascular morbidity and mortality has so far only been clearly proven for adults [6], a connection is plausible and likely in childhood and adolescence. This is another reason why studies with a focus on a possible positive influence on PWV with regard to the cardiovascular health of children and adolescents are of particular importance.

outlook

The reason for the study was the planned implementation of an exercise program that is to be integrated into everyday school life. The results of the follow-up examinations after one year will show whether this exercise program leads to a change in the described cardiovascular risk profile and in particular the PWV.

conclusion for practice

  • Children who are overweight or obese already show a low level of vascular elasticity when the PWV is measured.

  • A BMI> 90. Pzt. is associated with cardiovascular risk factors in terms of the incipient development of a metabolic syndrome.

  • Lower EBS is associated with higher BMI, higher cardiovascular risk, lower physical performance, and higher media consumption.

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