The correlation between blood pressure and waist circumference, body mass index, body fat percentage, physical activity and physical fitness in 1141 8th grade students from northern Germany
Background: Hypertension is one of the leading causes of mortality worldwide. Studies have shown that its’ development is associated with obesity, a sedentary life-style and stress. Obesity, one of the main risk factors for the development of hypertension, has become more and more prevalent in todays’ society. It is associated with the development of metabolic syndrome, cardiovascular diseases and chronic illnesses, such as diabetes. Even children and adolescents are nowadays more often obese. This might be due to the fact that a sedentary lifestyle and a lack in physical exercise have become more common. Studies theorize that the development of arterial hypertension starts as early as childhood. Thus the aim of this study was to find a correlation between high blood pressure and body mass index, body fat percentage and waist circumference in 1141 8th grade school children in northern Germany. Objective: The objective of this study was to analyse the correlation between blood pressure and waist circumference, body mass index and between body fat percentage. Another aim of this study was to find a correlation between blood pressure and physical activity and physical fitness. Materials and Methods: The data collection was conducted from January 2014 till February 2014 at 29 selected schools in the federal state of Schleswig-Holstein, northern Germany. The data was analysed using the Stata 14 (Stata Corp, College Station, TX). The students’ blood pressure was taken, BMI was calculated and body fat percentage and waist circumference were measured. To obtain data concerning physical activity and physical fitness, the school children were required to fill out a self-administered questionnaire with information about their weekly physical activity. Furthermore students participated in the 20m shuttle run test to obtain VO2max. Results: 1141 students were analysed. It was found that pathological or normal blood pressure values (mean systolic and mean diastolic values) are dependant on body mass index percentile (p<0.0001). 210 children out of 1136 had a body mass index value above the 90th percentile and were therefore obese. The statistical analysis proved that there is a strong correlation between waist circumference, body fat percentage (p=0.0178), as well as BMI percentile and blood pressure (p<0.001). Using regression analysis for blood pressure and waist circumference, as well as body fat percentage and BMI percentile, a statistically significant positive relation (p<0.001) between those factors and blood pressure were found. Body mass index percentile and waist circumference had the most significant effect on mean systole, whereas body-fat percentage showed the most significant effect on mean diastole. Our analysis additionally showed, that the amount of weekly physical activity had no significant effect on blood pressure. Conclusion: We found a strong correlation between body mass index, body fat percentage, waist circumference and blood pressure. Paediatricians should regularly monitor body mass index and waist circumference, since these parameters are easy to assess and show a high risk for the development of arterial hypertension later in life. Children with elevated body mass index or waist circumference should aim at losing weight and thereby controlling their risk of development of arterial hypertension. Physical exercise can help, as an instrument, to influence hypertension by aiding at weight loss, but the main emphasis should lie on losing weight and improvement of body composition. Weight control is more important than physical fitness and physical activity in children.