Physical activity but not sedentary time is associated with vitamin D status in adolescents: study of cardiovascular risk in adolescents (ERICA).

BACKGROUND/OBJECTIVES: The association between active lifestyle components and vitamin D status in adolescents remains relatively unexplored. We aimed to investigate independent and joint associations of moderate-to-vigorous physical activity (MVPA) and screen time with serum 25-hydroxyvitamin D [25(OH)D] concentrations in adolescents. METHODS: This multicenter cross-sectional study involved 1152 Brazilian adolescents (age 12-17 years). Serum 25(OH)D was measured in a single laboratory and categorized as ≤20, 21-29, or ≥30 ng/mL. Demographic and lifestyle characteristics were assessed by self-reports. Ordered logistic regression was used to investigate potential associations of being physically active (MVPA ≥ 300 min/week) and excessive screen time (>2 h/day) with serum 25(OH)D concentrations. RESULTS: The prevalence of higher serum 25(OH)D concentrations (≥30 ng/mL) was 36.4%. In adjusted models, being physically active was associated with higher serum 25(OH)D concentrations only in boys [proportional odds ratio (POR) = 2.04, 95% CI 1.42-2.93], while excessive screen time was not associated with serum 25(OH)D. Adolescents who were physically active and limited their screen time had higher odds of a higher serum 25(OH)D concentration, but the association was significant only for boys (POR = 2.11, 95% CI 1.19-3.74). CONCLUSIONS: MVPA may play an important role in increasing serum 25(OH)D concentrations in adolescence, especially for boys, regardless of screen time.

Waist-to-Height Ratio as a Predictor of C-Reactive Protein Levels.

BACKGROUND: C-reactive protein is an acute-phase protein that has been found in association with adiposity and cardiovascular disease risk. In this paper, the objective was to assess the relationship of C-reactive protein to four anthropometric measurements: body mass index, waist-to-height ratio, C index, and waist circumference. METHODS: A cross-sectional random sample of the Study of Cardiovascular Risk in Adolescents (Portuguese acronym "ERICA") was included in the study. The analysis was adjusted for the complex sampling design. Poisson regression models with robust variance were used to estimate a multivariate-adjusted prevalence rate ratio expressing the relationship of each anthropometric measure to C-reactive protein. We evaluated adolescents aged 12 to 17 years participating in the capital of Porto Alegre, Brazil. RESULTS: In all, 778 adolescents were included (60% female, 58% aged 15-17 years). Waist-to-height ratio was found to be the strongest adiposity marker associated with C-reactive protein even after adjusting for age, sex, smoking, physical activity, and insulin resistance (prevalence rate ratio = 7.09; 95% confidence interval, 5.01-9.18; p < 0.001). CONCLUSIONS: Waist-to-height ratio is a strong predictor of C-reactive protein in adolescents in Porto Alegre, Brazil.

The Study of Cardiovascular Risk in Adolescents--ERICA: rationale, design and sample characteristics of a national survey examining cardiovascular risk factor profile in Brazilian adolescents.

BACKGROUND: The Study of Cardiovascular Risk in Adolescents (Portuguese acronym, "ERICA") is a multicenter, school-based country-wide cross-sectional study funded by the Brazilian Ministry of Health, which aims at estimating the prevalence of cardiovascular risk factors, including those included in the definition of the metabolic syndrome, in a random sample of adolescents aged 12 to 17 years in Brazilian cities with more than 100,000 inhabitants. Approximately 85,000 students were assessed in public and private schools. Brazil is a continental country with a heterogeneous population of 190 million living in its five main geographic regions (North, Northeast, Midwest, South and Southeast). ERICA is a pioneering study that will assess the prevalence rates of cardiovascular risk factors in Brazilian adolescents using a sample with national and regional representativeness. This paper describes the rationale, design and procedures of ERICA. METHODS/DESIGN: Participants answered a self-administered questionnaire using an electronic device, in order to obtain information on demographic and lifestyle characteristics, including physical activity, smoking, alcohol intake, sleeping hours, common mental disorders and reproductive and oral health. Dietary intake was assessed using a 24-hour dietary recall. Anthropometric measures (weight, height and waist circumference) and blood pressure were also be measured. Blood was collected from a subsample of approximately 44,000 adolescents for measurements of fasting glucose, total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides, glycated hemoglobin and fasting insulin. DISCUSSION: The study findings will be instrumental to the development of public policies aiming at the prevention of obesity, atherosclerotic diseases and diabetes in an adolescent population.