ABC | Volume 112, Nº6, June 2019

Original Article Reuter et al Dyslipidemia and associated factors in schoolchildren Arq Bras Cardiol. 2019; 112(6):729-736 Participating schools were randomly selected in the year 2004, in the beginning of the “Schoolchildren’s Health” longitudinal study, in line with the population density of schoolchildren in the municipality. During the following cross-sectional analyses, all of the schoolchildren from the previously selected schools were invited to participate in the study. The initial sample was made up of 1,949 schoolchildren. However, 695 schoolchildren were excluded for the following reasons: refusal/impossibility of blood collection, non‑completion of fasting period before blood collection, failure to perform the CRF test, or incomplete filling out of questionnaire form. This study is part of the “Schoolchildren’s Health” study, which was approved by the Human Research Ethics Committee under certificate number 2525/10. This study follows the principles set forth by the Declaration of Helsinki. The schoolchildren’s parents or legal guardians signed free and informed consent forms. The sample size was calculated using the programG*Power 3.1 (Heinrich-Heine-Universität, Düsseldorf, Germany), using logistic regression as a statistical test (presence versus absence of dyslipidemia as dependent variable). Considering a statistical power of (1 − β ) = 0.95, a significance level of α = 0.05 and an odds ratio of 1.30, the minimum sample size estimated was 988 schoolchildren. Blood samples were collected after a 12-hour fasting period. Serum samples were used to determine triglycerides (TG), total cholesterol (TC), and high-density lipoprotein cholesterol (HDL-c). The tests were carried out using Miura One automated equipment (I.S.E., Rome, Italy). Low-density lipoprotein cholesterol (LDL-c) levels were calculated using the Friedewald, Fredrickson, and Levy formula. 10 International cutoff points were used to classify the lipid profile. 11 Dyslipidemia was considered as the presence of alterations in at least one component of the lipid profile (increased TG, TC, or LDL-c or decreased HDL-c, without considering borderline cases). Levels of CRF were evaluated by the 12-minute run/walk test, recommended by the Projeto Esporte Brasil (Brazil Sport Project; PROESP-BR), 12 which consists of covering the longest distance possible in 12 minutes on a previously marked track. Researchers with degrees in Physical Education who are a part of this study applied the test, with assistance from previously trained students of Physical Education receiving scholarships. Schoolchildren were instructed to wear light clothing and tennis shoes on evaluation day. Data were classified using cutoff points defined by PROESP-BR. 12 Cultural habits were evaluated using the adapted Barros and Nahas questionnaire, 13 which was self-reported by the schoolchildren. Amount of time spent watching TV was categorized into two categories: 1) less than two hours per day and 2) two hours per day or more. School transport was considered either active (by foot or by bike) or sedentary (car, motorcycle, or collective transport). Eating habits were evaluated by the weekly frequency with which schoolchildren consumed the following foods: 1) sweets, 2) soft drinks, 3) fried salty snacks, and 4) pizza/lasagna. Consumption was classified as “never/sometimes” (not at all/once a week) and “almost always/always” (twice or more than twice weekly). Statistical Analysis Data analysis was carried out using the statistical program SPSS v. 23.0 (IBM, Armonk, USA). Descriptive data were expressed in absolute and relative frequency. The association between dependent variables (dyslipidemia and increased levels of any lipid profile parameter) and cultural habits was tested via logistic regression. Values were described in odds ratios (OR) and confidence intervals (CI) at 95%. Initially, univariate analysis of data was conducted. Subsequently, adjusted analysis of variables that showed significance was applied. Data with p < 0.05 were considered significant. Results Descriptive data are shown in Table 1. Dyslipidemia was observed in 41.9% of schoolchildren. The condition was more prevalent in females, adolescents, and schoolchildren with low CRF levels (p < 0.05). The data described in Table 2 indicate that dyslipidemia was significantly associated with female sex and overweight/ obese status. Adolescents had lower chances of developing dyslipidemia, in comparison with children. In the univariate analysis, low levels of CRF were associated with dyslipidemia. This association, however, was not maintained in the multivariate analysis. Furthermore, cultural aspects were not associated with dyslipidemia. When comparing data for lipid profile components, in as isolated manner, high levels of TC were observed to be associated with female sex. Adolescents had higher chances of increased TC and TG levels than children. Overweight/obese status is associated with increased TC and TG (Table 3). Low levels of HDL-c are associated with the habit of watching TV for 2 or more hours per day. Female sex, adolescent age range, and sedentary school transport were associated with increased LDL-c (Table 4). Discussion A high prevalence of dyslipidemia in schoolchildren has constituted increasingly frequent alterations in Brazilian children and adolescents. Studies conducted in Recife, Pernambuco (29.7%), 14 Florianópolis, Santa Catarina (22.0%), 15 and Londrina, Paraná (20.8%) 16 indicate a growing prevalence of dyslipidemia in schoolchildren in different regions of the country. In Birjand, Iran, similar estimates indicated that the prevalence of dyslipidemia has affected 31% of children between 6 and 11 years of age, with girls presenting a higher prevalence of hypertriglyceridemia and boys a higher prevalence of hypercholesterolemia. 17 It is worth highlighting, however, that the high prevalence found in this study (41.9%) exceeds these already high estimates. Furthermore, data from a 10-year trend study (2004–2014) of serum lipid levels and dyslipidemia, conducted with 3,249 schoolchildren between the ages of 6 and 18 from several schools in Beijing, demonstrated that the prevalence of dyslipidemia, based on elevated levels of TG and TC and reduced HDL-c, significantly increased during the period. This suggests an upward trend in this prevalence and constitutes a warning that continuous measures are necessary to curb this condition. 18 730