Resting blood pressure and cardiovascular response to sympathetic stimulation in adolescents.

The prevalence of significant hypertension in childhood may be higher than expected. We have measured sitting blood pressure in 168 11-yr-old children attending a pre-high school in the Neapolitan area on four occasions over a 3-month period. We have also measured blood pressure and heart rate during a mental arithmetic test and during isometric exercise. Prevalence of significant hypertension (diastolic blood pressure 82-90 mmHg) was 13% at the first visit and decreased to 6.5% at the last visit; prevalence of severe hypertension (diastolic blood pressure greater than or equal to 90 mmHg) decreased from 5.4% to 1.2% from the 1st to the 4th visit. No sex-related difference was observed. A more frequently positive family history of hypertension (50% vs 30% in the fifth and first quintile of blood pressure, respectively) and higher body weight (body mass index = 21.4 vs 19.3 kg/m2) were found in children in the 5th quintile of blood pressure distribution. Blood pressure increased during mental arithmetic by 10/13% of the resting values in the first quintile and by 6/11% in the last one during mental test; during handgrip the increase was of 20/37% and 24/46%, respectively: differences between quintiles did not reach statistical significance. These data show that about 8% of a Neapolitan sample of school population have high blood pressure levels, while no difference in vascular reactivity to sympathetic stimulation was detected in children with higher blood pressure.

Weight reduction lowers blood pressure independently of salt restriction.

The existence of a link between obesity and hypertension is nowadays universally accepted; however, there are still some doubts about the fact that weight reduction induces a significant long-term decrease in blood pressure. This clinical trial aimed at evaluating the effects of marked weight loss (at least 30% of excess body weight) induced by a low-energy (600 Kcal), normal sodium diet in severely obese patients, on blood pressure at rest and during sympathetic stimulation. Eight of the 20 patients initially recruited for the study were able to reach the therapeutical goal and brought their body weight from 107 +/- 6 to 91 +/- 4 kg. Their blood pressure (BP) at rest was at the same time reduced from 137/81 +/- 5/4 to 122/74 +/- 4/4 mmHg. Also, blood pressure measured during three different stimuli (cold pressor test, handgrip and mental arithmetic test) was lowered by this nonpharmacological means. These effects are related solely to weight reduction, since no change in salt intake occurred, as demonstrated by measurements of the 24-h sodium excretion test (191 +/- 13 vs 185 +/- 10 mEq/24 h). In conclusion, these results support the hypothesis that a drastic weight loss, independently of salt restriction, significantly reduces BP at rest and during stimulation of the adrenergic nervous system.

Responses of serum insulin and blood pressure to cold and handgrip in obese patients.

A close correlation between body weight and blood pressure has been frequently observed in both clinical and epidemiological studies. The aim of this clinical trial was to evaluate whether, in obese patients, there is any relationship between blood pressure, at rest or during sympathetic stimulation, and blood glucose and serum insulin, both while fasting and during an oral glucose challenge. Twenty obese patients (age 26-65 years, body weight 97 +/- 16 kg, 11 normotensive and 9 hypertensive) entered the study. After a 4-week run-in period on an isocaloric diet with normal intake of sodium, blood pressure and heart rate were measured at rest and during sympathetic stimulation induced by cold and isometric testing. Responses of glucose and insulin to a standardized 75 g oral glucose tolerance test were also evaluated. The responses of glucose and insulin to glucose challenge were not statistically different in normotensive and hypertensive obese patients. Levels of insulin in the serum in the serum in the fasting state and during glucose load were significantly correlated with the response of blood pressure to cold and isometric exercise, but not to blood pressure at rest. The response of heart rate to cold was closely related to insulin only in the subgroup of normotensives. The present findings support the hypothesis that the sympathetic nervous system, which influences secretion of insulin and regulation of blood pressure, is involved in the pathophysiology of the association of obesity and hypertension.

Cardiovascular response to mental stress and to handgrip in children. The role of physical activity.

Cardiovascular responses to sympathetic stimulation may be altered in the early phases of life of subjects with a family history of hypertension. The possible influence of physical activity on adrenergic modulation in children is still not well known. In this study we evaluated, in a group of 162 11-year-old children from a secondary school near Naples, blood pressure and heart rate measured 4 times at 3-week intervals at rest and during adrenergic system stimulation by mental arithmetic stress and isometric exercise. Children were divided into sedentary and physically active groups according to the levels of a Saltin modified questionnaire. Family history of hypertension was also investigated. Systolic and diastolic blood pressure at rest were slightly higher in the sedentary group at each control (107/75 +/- 11/11 vs 105/73 +/- 11/11 mmHg at the first and 100/70 +/- 14/14 vs 98/69 +/- 9/9 at the last control); heart rate in the same group was higher as well (91 +/- 11 vs 87 +/- 12 beats/min, p less than 0.02 at the first and 80 +/- 9 vs 77 +/- 11 at the last control). Systolic and diastolic blood pressure increased by 7/15% during mental stress and by 23/45% during isometric exercise in the sedentary group. The corresponding blood pressure increases in the physically active group were 6/12% and 20/40%, respectively. These responses were independent of sex, body weight and family history of hypertension. These results support the hypothesis that regular physical activity in young adolescents only mildly influences resting blood pressure and cardiovascular responses during the stimulation of the sympathetic nervous system.

Body weight and cardiovascular response to sympathetic stimulation in childhood.

The possible relationship between cardiovascular response to adrenergic stimulation and body weight has been studied in 166 eleven-year-old students (103 male, 63 female). Resting blood pressure (BP) by random-zero machine, heart rate (HR) and body weight (BMI) were measured four times in the school at 3-week intervals. On the third visit a mental arithmetic stress was carried out and a 24 h urine specimen was collected for the measurements of catecholamine excretion. On the fourth visit students carried out an isometric exercise (handgrip). Girls were more frequently found in the last quintiles of BMI (10/33 in the first vs 19/33 in the fifth). This might be due to a more advanced sexual maturation. BP at rest significantly increased with body weight (from 105/81 +/- 11/13 mmHg in the first to 119/87 +/- 10/12 in the fifth quintile). In each quintile no sex-related difference was observed in BP or HR. A marked cardiovascular response was observed during both tests without significant difference among quintiles. The 24 h urinary excretion of total catecholamines slightly increased with body weight (from 26.2 +/- 11 micrograms/24 h in the first to 34.5 +/- 19.5 micrograms/24 h in the fifth quintile). These data in a population of 11-year-old students therefore support the hypothesis that although BP at rest is influenced by BMI, the cardiovascular response to adrenergic stimulation is independent of body weight.