Prevalence of hypertension and decreased glomerular filtration rate in obese children: results of a population-based field study

Background. Obesity has risen considerably in the Western world and the trend is increasing in non-Western, developing countries, as well. Several school screening studies showed the relation between body mass index and hypertension. In adults, obesity is associated with an increased risk of development and progression of kidney disease. However, data at the epidemiological level are limited, both for children and adults. The aim of this study was to determine the prevalence of obesity and evaluate its association with hypertension and glomerular filtration rate (GFR) among children in Turkey. Methods. A population-based field study in which individuals were accessed by house visits throughout Turkey has been conducted. The study sample (3622 children; 5-18 years; 49.6% female, mean age 11.88 +/- 3.40 years) was selected to represent the Turkish population regarding geographical region, gender and age (5-18 years). Obesity was defined as the body mass index >= 95th percentile for age and gender. The Schwartz formula was used to estimate GFR. Blood pressure (BP) percentile was determined according to age, gender and length. Results. The prevalence of overweight, obesity and hypertension were 9.3, 8.9 and 6.1%, respectively. Logistic regression analysis revealed urban area (OR 1.50; 95% CI 1.15-1.96; P = 0.003) as an independent risk for obesity and age decreased (OR 0.921; 95% CI 0.890-0.924; P < 0.001) risk for obesity. Obese children had the highest rate of hypertension (11.4 versus 5.6%; P < 0.001; OR 2.17, 95% CI 1.49-3.17; P < 0.001) and stage II hypertension (3.8 versus 0.7%; OR 6.01, 95% CI 2.93-12.33; P < 0.001). Systolic and diastolic BP z-scores were significantly higher in obese children. The mean estimated (eGFR) was lower in obese children (122.7 +/- 21.6 versus 129.4 +/- 23.1, P < 0.001). The rates of children with eGFR < 90 and < 75 mL/min/1.73 m(2) were higher in obese patients, but did not reach statistical significance. Conclusions. Our nation-wide population-based field study among children showed that the prevalence of obesity is increasing in Turkey. The prevalence of hypertension and stage II hypertension, BP z-scores and eGFR were associated with obesity. We suggest that obese children are future candidates for chronic kidney disease. Longitudinal research is necessary to better understand these associations. Strategies for the prevention and management of obesity are also important for emerging countries and for children.