Population-based hypertension screening in preschool children

Abstract

Hypertension is the leading risk factor for cardiovascular diseases in adults. Due to the common lack of clinical symptoms, hypertension frequently remains undiagnosed and untreated until late in the course of disorder [1, 2]. In contrast to adults, hypertension in childhood is preferentially due to secondary causes, most commonly renoparenchymal disease [3, 4]. Routine blood pressure measurements are still rarely performed by general paediatricians, and the prevalence of essential hypertension in children may be underestimated due to diagnostic neglect. Blood pressure during adolescence clearly tracks at least into early and middle adult age (“tracking” of blood pressure) [5]. Children in the top quintile of systolic blood pressure are 3–4 times more likely to develop clinical hypertension by age 30 than their peers, and 50% of hypertensive adults had elevated childhood systolic blood pressure [6]. The minimal age at which significant blood pressure tracking into adult life becomes manifest has not been determined. There are a number of possible explanations for the phenomenon of blood pressure tracking. The “fetal origins” hypothesis assumes that malnutrition during critical intrauterine growth periods leads to life-long programming of the cardiovascular system [7]. Obesity is another major determinant of childhood blood pressure. A significant association between systolic blood pressure and the body mass index has been demonstrated already in preschool children [8]. Moreover, socio-economic condition may play an independent role; associations of living conditions in childhood with adult blood pressure have been described [9]. Finally, genetic factors predisposing to hypertension would be expected to be operative already in childhood. The diagnosis of hypertension in childhood is rendered difficult by several factors. Due to the lack of outcome studies, hypertension is defined by the deviation of blood pressure from the distribution in the general population. Since blood pressure changes dynamically throughout childhood [10–12], it is critical to have a firm basis for the normal range of blood pressure at different ages and heights. Another important methodological issue is the unknown equivalence of auscultatory measurements with oscillometric readings. While semi-automatic oscillometric devices are rapidly gaining ground in the pediatric field, very few validation studies have been performed with individual devices. These suggest systematic differences between the methods in the pediatric age group, indicating a need for specific centile curves based on oscillometric measurements.