[Evaluation of risk factors associated with increased blood pressure in children]

[Article in Portuguese]

Garcia FD, Terra AF, Queiroz AM, Correia CA, Ramos PS, Ferreira QT, Rocha RL, Oliveira EA.

Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG, Brazil.

OBJECTIVE: To identify factors associated with increased arterial blood pressure in children. METHODS: In this cross-sectional study, arterial blood pressure was measured in 672 children between 2 and 11 years of age from two schools in the city of Belo Horizonte, Brazil. After providing informed consent, all children had their blood pressure and anthropometric parameters measured. Blood pressure was measured based on the recommendations of the Update on the 1987 Task Force Report on High Blood Pressure in Children and Adolescents. The following variables were assessed: age, sex, race, urban life quality index, weight, height, and body mass index. Analysis of variance was used for comparison of means and the chi-square was used for comparison of proportions. Variables associated with increased blood pressure were included in a multiple regression model. RESULTS: According to univariate analysis, increased systolic and diastolic blood pressure were associated with high urban life quality index, white race and high body mass index. On multivariate analysis, body mass index, urban life quality index and height remained associated with increased systolic blood pressure; urban life quality index and age were associated with increased diastolic blood pressure. CONCLUSION: In this study, excess weight and obesity were associated with increased systolic blood pressure. Other unidentified factors were partially associated with increased blood pressure in children from the school with elevated urban life quality index.

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[Prevalence of high blood pressure in children and adolescents from the city of Maceio, Brazil]

[Article in Portuguese]

Moura AA, Silva MA, Ferraz MR, Rivera IR.

Universidade Federal de Alagoas (UFAL), Maceio, AL, Brazil. adriana_avila uol.com.br

OBJECTIVES: To define the prevalence of high blood pressure in a representative sample of children and adolescents from the city of Maceio, state of Alagoas, Brazil, and to investigate the association of high blood pressure with age, sex and nutritional status. METHODS: This cross-sectional study was carried out from May 2000 to September 2002. Individuals between 7 and 17 years of age were selected among all the 185,702 students from public and private schools. The size of the sample was defined based on the expected prevalence of hypertension for the age group. After randomization, data were collected through a questionnaire. Blood pressure was measured twice. Weight and height were also measured. High blood pressure was defined as systolic and/or diastolic blood pressure over the 95th percentile in one or in both measures. RESULTS: The final sample included 1,253 students (706 females). One hundred and eighteen students had high blood pressure (mean age 13 years; 44% males). Risk of being overweight and excess weight were identified, respectively, in 9.3 and 4.5% of the students. These variables were significantly associated with high blood pressure. CONCLUSIONS: The prevalence of high blood pressure was 9.4%. High blood pressure was significantly more frequent among overweight students and among those at risk for being overweight.

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Ambulatory blood pressure monitoring in normotensive individuals undergoing two single exercise sessions: resistive exercise training and aerobic exercise training.

[Article in English, Portuguese]

Bermudes AM, Vassallo DV, Vasquez EC, Lima EG.

Universidade Federal do Espirito Santo - Escola Superior de Ciencias da Santa Casa de Misericodia de Vitoria, EMESCAM, Vitoria, ES Brasil.

OBJECTIVE: To assess the influence of 2 single exercise sessions on blood pressure in sedentary normotensive individuals: one of resistive exercise training (circuit weight training) and the other of aerobic exercise training. METHODS: Using ambulatory blood pressure monitoring, this study assessed 25 individuals as follows: in a controlled situation at rest (ABPM 1); after resistive exercise training (ABPM 2); and after aerobic exercise training (ABPM 3). Resistive exercise training was performed as circuit weight training with an intensity of 40% of each individual's maximum strength. The aerobic exercise training was performed on a cycloergometer with intensity between 60% and 70% of the maximum heart rate (HR) reached during previous exercise testing. RESULTS: Systolic blood pressure (SBP) values during 24 hours and during subperiods of wakefulness and sleep showed no statistically significant variations when the results obtained at rest were compared with those of ABPM2 and ABPM3, and when the results of ABPM2 were compared with those of ABPM3. The mean heart rate during 24 hours and in the wakefulness period showed significant increases (P<0.05), when ABPM2 was compared with ABPM3. CONCLUSION: A single session of resistive exercise training in normotensive individuals was sufficient to cause significant reductions in blood pressure levels after exercise in the period of sleep. The session of aerobic exercise training in these same individuals was more effective in significantly reducing blood pressure levels.

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Sympathetic activity is reduced by nCPAP in hypertensive obstructive sleep apnoea patients.

Heitmann J, Ehlenz K, Penzel T, Becker HF, Grote L, Voigt KH, Peter JH, Vogelmeier C.

Sleep Laboratory, Division of Pulmonary Diseases, Dept of Internal Medicine, Marburg University, Germany. heitmanj med.uni-marburg.de

There is increasing evidence that nasal continuous positive airway pressure (nCPAP) lowers blood pressure in obstructive sleep apnoea (OSA) patients, not only during sleep but also in the daytime. However, both the mechanisms of blood pressure reduction and the considerable differences in the magnitude of the effect in the studies presented to date are not fully understood. Therefore, the authors prospectively studied the effect of nCPAP on noradrenaline plasma levels (NApl), blood pressure and heart rate (HR) in 10 normotensive and eight hypertensive OSA patients before and after 41.6 +/- 16.9 days of nCPAP therapy. Polysomnography and invasive blood pressure were continuously monitored over 24 h in the supine position before and with nCPAP. NApl were analysed every 15 min. In hypertensives, nCPAP reduced NApl by 36 +/- 25%, lowered mean arterial blood pressure substantially (night-time: -8.89 +/- 14.09 mmHg; daytime: -7.94 +/- 10.47 mmHg) and decreased HR by 6.6 +/- 5.4 beats x min(-1), whereas in normotensives there were only minor changes. The decrease in heart rate was associated with a decrease in mean arterial blood pressure and noradrenaline plasma levels, suggesting a causal effect of nasal continuous positive airway pressure therapy. This nasal continuous positive airway pressure effect occurs mainly in hypertensive obstructive sleep apnoea patients, whereas the effect is small in normotensives. This may explain, at least in part, some of the discrepant results in previous treatment studies.

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The relationship between body mass index, blood pressure and pulse rate among normotensive and hypertensive participants in the third National Health and Nutrition Examination Survey (NHANES).

Martins D, Tareen N, Pan D, Norris K.

Department of Medicine, Charles R. Drew University, 1731 East 120th Street MP11, Los Angeles, California 90059, USA.

Obesity is associated with high insulin and leptin levels. Studies also suggest that high levels of insulin and leptin increase sympathetic nervous system (SNS) activity and engender increased chronotropy, vasoconstriction and antinatriuresis that may contribute to the pathogenesis of obesity related hypertension. Sympathetic modulation of cardiovascular responses requires good baroreceptor sensitivity and optimal vascular compliance. The vascular changes associated with isolated systolic hypertension (ISH) have been shown to modify baroreceptor sensitivity and vascular compliance and may mitigate sympathetic modulation of cardiovascular responses and attenuate the hypertensive effect of obesity. The purpose of this study is to examine the differences in the relationship between body mass index, pulse rate (PR), systolic blood pressure (SBP) and diastolic blood pressure (DBP) among participants with normal blood pressure and ISH using data from the third National Health and Nutrition Examination Survey. Data from 13,761 non-institutionalized adults 18 years and older not receiving antihypertensive therapy were analyzed. Results showed that PR, SBP and DBP increase with increasing BMI. The rise in PR, SBP and DBP with BMI is higher among participants with normal blood pressure than among those with ISH. We concluded that increasing level of obesity is associated with a rise in pulse rate and blood pressure but the effect of obesity on blood pressure and pulse rate might be weaker among participants with ISH.

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[A 20-year prospective study on risk factors for myocardial infarction of 5,137 men in Capital Steel and Iron Company]

[Article in Chinese]

Yue H, Gu DF, Wu XG, Yu XH, Duan XF, Wang JH, Zheng RP, Zhou J.

Cardiovascular Institute of Fuwai Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100037, China.

OBJECTIVE: To identify independent risk factors for myocardial infarction (MI) in Chinese men and to develop a model to predict risk profile of an individual suffering MI. METHODS: Study sample included 5 137 men aged 45.2 +/- 7.8 years who came from a cohort in Beijing Capital Steel and Iron Company, based on the three surveys on coronary heart disease conducted in 1974, 1979 and 1980, respectively. Demographic data and other risk factors, such as life style, medical history, blood pressure, total serum cholesterol level (TC), etc. were collected according to the same protocol in 1980. All the participants were followed up for MI in an average period of 20.84 years until 2001. RESULTS: (1) There were 122 cases with MI identified during the period of follow-up, with an incidence of MI 117.4 per 100 000 person-years. Age of more than 50, smoking, higher systolic and diastolic blood pressure (SBP and DBP) levels, higher TC all were identified as important risk factors of MI. (2) Incidence of MI increased with TC. An increment of 0.52 mmol/L of TC significantly increased relative risk of MI by approximately 40% after adjusted for age, blood pressure and smoking. (3) An increment of 20 mm Hg in SBP or 10 mm Hg in DBP associated with a 40% increase in incidence of MI, adjusting for age, TC and smoking. (4) Smoking was the most risky factors for MI. Smokers had 2.3 times risk of MI, after as compared to non-smokers (or its incidence increased by 137%), after adjusting for blood pressure, TC and age, etc. (5) Incidence of MI increased by 20% with increment of five-year of age in those aged over 50 (P < 0.05), after adjusting for blood pressure, TC and smoking. And, (6) finally, based on multivariate logistic and Cox regression analyses, a model containing several risk factors, such as age, blood pressure, TC and smoking, was developed to predict individual's risk for afflicting MI. CONCLUSIONS: Results of this prospective study showed several established risk factors for MI, including age, blood pressure, TC and smoking all as independent predictors of MI in Chinese men. It is clear and rational that intervention and modification of those traditional risk factors can lead to a decrease in coronary events in Chinese population.

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Does breast-feeding in infancy lower blood pressure in childhood? The Avon Longitudinal Study of Parents and Children (ALSPAC).

Martin RM, Ness AR, Gunnell D, Emmett P, Davey Smith G; ALSPAC Study Team.

Department of Social Medicine, University of Bristol, Bristol, UK. richard.martin bristol.ac.uk

BACKGROUND: Breast-feeding in infancy has been associated with decreased coronary heart disease mortality, but the underlying mechanisms are unclear. We investigated the association of breast-feeding with blood pressure in a contemporary cohort. METHODS AND RESULTS: In a prospective cohort study (ALSPAC, United Kingdom), a total of 7276 singleton, term infants born in 1991 and 1992 were examined at 7.5 years. Complete data were available for 4763 children. The systolic and diastolic blood pressures of breast-fed children were 1.2 mm Hg lower (95% CI, 0.5 to 1.9) and 0.9 mm Hg lower (0.3 to 1.4), respectively, compared with children who were never breast-fed (models controlled for age, sex, room temperature, and field observer). Blood pressure differences were attenuated but remained statistically significant in fully adjusted models controlling for social, economic, maternal, and anthropometric variables (reduction in systolic blood pressure: 0.8 mm Hg [0.1 to 1.5]; reduction in diastolic blood pressure: 0.6 mm Hg [0.1 to 1.0]). Blood pressure differences were similar whether breast-feeding was partial or exclusive. We examined the effect of breast-feeding duration. In fully adjusted models, there was a 0.2-mm Hg reduction (0.0 to 0.3) in systolic pressure for each 3 months of breast-feeding. CONCLUSIONS: Breast-feeding is associated with a lowering of later blood pressure in children born at term. If the association is causal, the wider promotion of breast-feeding is a potential component of the public health strategy to reduce population levels of blood pressure.

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Overweight, ethnicity, and the prevalence of hypertension in school-aged children.

Sorof JM, Lai D, Turner J, Poffenbarger T, Portman RJ.

Department of Pediatrics, Division of Pediatric Nephrology and Hypertension, University of Texas Health Science Center, Houston, Texas, USA. jonathan.m.sorof uth.tmc.edu

OBJECTIVES: To describe the current prevalence of pediatric hypertension and the relationships between gender, ethnicity, overweight, and blood pressure. METHODS: School-based screening was performed in 5102 children (13.5 +/- 1.7 years) from May through November 2002. Age, gender, ethnicity, weight, and height were ascertained, and body mass index (BMI) was calculated as weight (kg)/height (m2). Overweight was defined as BMI > or =95th percentile. Students with blood pressure >95th percentile on the first screening underwent a second screening 1 to 2 weeks later, and then a third screening if blood pressure was >95th percentile at the second screening. RESULTS: Ethnicity distribution was 44% white, 25% Hispanic, 22% African American, and 7% Asian. Overall, overweight prevalence was 20%, which varied significantly by ethnicity (31% Hispanic, 20% African American, 15% white, and 11% Asian). The prevalence of elevated blood pressure after first, second, and third screenings was 19.4%, 9.5%, and 4.5%, respectively. Elevated blood pressure on first screening was highest among Hispanics (25%) and lowest among Asians (14%). Ethnic differences in the prevalence of hypertension (elevated blood pressure on 3 screenings) were not significant after controlling for overweight. The prevalence of hypertension increased progressively as the BMI percentile increased from < or =5th percentile (2%) to > or =95th percentile (11%). After adjustment for gender, ethnicity, overweight, and age, the relative risk of hypertension was significant for gender (relative risk: 1.50; confidence interval: 1.15, 1.95) and overweight (relative risk: 3.26; confidence interval: 2.50, 4.24). CONCLUSIONS: These results confirm an evolving epidemic of cardiovascular risk in youth, as evidenced by an increase in the prevalence of overweight and hypertension, notably among ethnic minority children.

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