Prevalence of arterial hypertension among Brazilian adolescents: systematic review and meta-analysis

BACKGROUND: Cardiovascular diseases are the leading cause of death in the world and are responsible for a high number of disability-adjusted life years. Elevated blood pressure is an independent, linear and continuous risk factor for cardiovascular disease and has also been reported in the young population. Brazil is a country of continental dimensions, and is very heterogeneous with respect to socioeconomic and cultural aspects. Brazilian studies on the subject of hypertension in adolescence are not nationally representative, and this provides a rationale for the conduction of a meta-analysis to assess the magnitude of the problem in the country. METHODS: Hypertension studies in adolescents published from 1990 to September 2010 were searched in six electronic databases. Forest plots of the prevalence of hypertension were built for the overall population and by gender. Heterogeneity was assessed using I2 statistics. Meta-regression models were adjusted in order to identify possible sources of heterogeneity. RESULTS: Of 3,631 articles initially identified, 17 were considered eligible for systematic review. The pooled prevalence of hypertension, estimated through random effects models, was 8.12% (95% CI 6.24-10.52) for the total population. Overall, prevalence was higher in males, 8.75% (95% CI 5.81-12.96) than females, 6.31%, (95% CI 4.41-8.96). Several variables were investigated in the heterogeneity analysis: region of the study, sample size, age and method of blood pressure measurement. The only variables that partially and inconsistently explained the observed heterogeneity (I2 = 95.3%) were the region of the country where the study was conducted and sample. CONCLUSIONS: There was a large variation in hypertension prevalence and in the methods used for its evaluation throughout studies with Brazilian adolescents, indicating the need for standardized procedures and validated methods for hypertension measurement. Despite the large observed heterogeneity, and the small number of studies in some regions of Brazil, the pooled prevalence found in both males and females shows that systemic arterial hypertension should be monitored in the population aged 10-20 years and that specific measures are required to prevent and control the disease, as well as its risk factors. Studies that compare regional heterogeneities may contribute to the knowledge of factors associated with increased blood pressure among adolescents.