Group for Cardiovascular Disease and Epidemiological Transition : G.C.T.

Prevalence and determinants of high blood pressure in children aged 11-13 years:
a population-based study in Switzerland

 

Investigators:  Pascal Bovet, Michel Burnier, Arnaud Chiolero, François Cachat, Fred Paccaud
Study coordinator:  Arnaud Chiolero

Funding:  Swiss National Science Foundation

Background: High blood pressure (HBP) is the leading contributor to the avoidable burden of cardiovascular disease (CVD) in adult populations. HBP is less common in children and often found to be secondary to renal and other diseases. The increase in prevalence of overweight in children is likely to produce a commensurate increase in the prevalence of primary (essential) HBP in children, which may in turn further increase the epidemic of hypertension in adults. However, assessing the situation of HBP in children has been limited due to the lack of universal definition of HBP in children and the paucity of population-based data, including in Europe and in Switzerland. Therefore, it is important to gain knowledge on the distribution of BP in children and its associated conditions and determinants in order to develop relevant prevention and control measures.

Working hypotheses:  Among children aged 11-13,

Aims of the study:

Part 1)  To describe the distribution of BP in a population-based sample of children aged 11-13:

  1. To compare the sex-, age-, and height-specific percentiles of BP in a Swiss population with those of the reference US population,
  2. To assess the prevalence of persistent HBP and evaluate the positive predictive value of BP readings taken on a single occasion for identifying persistent HBP,
  3. To compare various BP measurement methods in children with HBP, i.e. repeated readings at school, ABPM, and self-measured readings at home.

Part 2)  To explore selected determinants of HBP:

  1. To investigate the association of BP with selected early life factors (e.g. birth weight, maternal smoking) taking advantage of the availability of neonatal data for most children targeted by Part I,
  2. To examine the relationships between BP, body weight, and selected other variables,
  3. To compare the prevalence of urine markers of renal impairment in children with HBP and in controls.

Study design and methods:

All schoolchildren in the 6th grade in 2005-06 in the Canton of Vaud (~7’400, age 11-13) will be invited to participate. Such large sample will allow defining robust BP percentiles. The 6th grade has been selected because neonatal and maternal data are already available for most of these children (the “EDEN study”, which examined all babies born in canton of Vaud in 1993-94). For all children, nurses will gather, using standardized tools, (a) anthropometric data and BP, and (b) data on physical activity, diet and smoking habits (self-administered questionnaire). Selected characteristics will be obtained from the parents of all children through a mailed questionnaire. Nurses will measure BP at school on up to 3 separate days whenever BP is elevated in order to identify persistent HBP. ABPM and home BP measurements will be obtained in children with persistent HBP. A urine spot sample will be obtained in children with persistent HBP and in a random sample of normotensive children to assess markers of renal pathology (dipstick, electrolytes, albuminuria).

Expected value of the proposed project:

  1. From a public health perspective, this study will update the current epidemiological situation on HBP and overweight and help inform public health measures to prevent HBP and overweight in children.
  2. From an etiological perspective, the study will allow examining the relation between BP and determinants such as parents’ characteristics, perinatal conditions, child’s weight and other variables.
  3. From a clinical perspective, the study will allow evaluating and refining procedures for the diagnosis and management of HBP in children, including the relative frequency of primary and secondary HBP.

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