Alexandre Romero

Desenvolvimento e validação de um questionário de avaliação da atividade física para adolescentes

OBJETIVO: Desenvolver um questionario de atividade fisica para adolescentes brasileiros e verificar sua validade e reprodutibilidade. METODOS: Participaram do estudo 94 adolescentes (30 meninos e 64 meninas) com idade entre 11 a 16 anos, em 2004. O questionario foi composto por 17 questoes sobre atividades habituais exercidas nos ultimos 12 meses (exercicios fisicos/esportes e atividades de locomocao) e foi padronizado para gerar escores semanal e anual. Como metodo de referencia utilizou-se o teste de corrida vai-e-vem de 20 metros com as variaveis tempo em minutos, velocidade maxima em km/h, consumo maximo de oxigenio e frequencia cardiaca maxima. Para a analise de validacao, foram utilizados o coeficiente de Spearman e correlacao ajustada por idade. Para a analise da reprodutibilidade, utilizou-se medida repetida com intervalo de 15 dias e coeficiente de correlacao intraclasse. RESULTADOS: Para o escore semanal de atividade fisica, os maiores coeficientes de correlacao foram obtidos com o tempo total para a analise em conjunto (r=0,19), velocidade total para os meninos (r=0,20), e consumo maximo de oxigenio e tempo total para as meninas (r=0,17). Para o escore anual de atividade fisica, os maiores coeficientes de correlacao foram obtidos com o tempo total para a analise em conjunto (r=0,30), frequencia cardiaca final apos o ajuste pela idade para os meninos (r=0,22) e tempo total para as meninas (r=0,23). Nas analises de reprodutibilidade, a correlacao do escore semanal foi de 0,61 e a do escore anual foi de 0,68. CONCLUSOES: O questionario apresentou evidencias de validade e reprodutibilidade. Recomenda-se sua utilizacao para avaliacao da atividade fisica habitual em estudos epidemiologicos com adolescentes.

Determinantes do índice de massa corporal em adolescentes de escolas públicas de Piracicaba, São Paulo

The objective of this study was to assess determining factors of body mass index (BMI) in adolescents enrolled in public schools in Piracicaba, Sao Paulo. The sample had 328 adolescents from both genders; minimum age was 10 years old. We have assessed weight, height, sexual maturity, physical activity, and diet. A multiple linear regression model was used to assess the association between independent variables and BMI. While girls considered physically active presented greater mean BMI than those insufficiently active, boys did not present statistical difference between mean BMI among those active and those insufficiently active. Sexual maturity was a determinant for BMI, for both genders, reinforcing the idea that it is essential to take this variable into account in studies that assess the nutritional situation in adolescents. We believe that the methods used in the present study, which are normally used in similar surveys, have important limitations to assess the influence of variables such as the level of physical activity and food intake on the BMI of adolescents. Thus, it is important to improve these methods and adopt them in further studies.

Validity and reliability of self-reported weight and height measures for the diagnoses of adolescent's nutritional status

PURPOSE: To assess the validity and reliability of self-reported height, weight, and Body Mass Index (BMI) to diagnose the nutritional status of adolescents. METHODS: The study included 360 public school students of both genders, with ages ranging from 10 to 15 years. Adolescents self-reported their weight and height, and these values were later obtained directly by interviewers. The validity of BMI based on self-reported measures was calculated using sensitivity and specificity indexes, and positive predictive value (PPV). Agreement between self-reported and measured BMI was evaluated using Kappas weight coefficient, the Lin correlation coefficient, and Bland-Altman and Lins plots. RESULTS: Both girls and boys underestimated their weight (-1.0 girls and boys) and height (girls - 1.2 and boys - 0.8) (p < 0.001). BMI presented moderate agreement between measured and self-reported values. Sensitivity of estimated BMI based on reported measures to classify obese subjects was higher for boys (87.5%) than it was for girls (60.9%), whereas specificity was higher for girls (92.7%) than it was for boys (80.6%). PPV was high only for classification of normal-weight adolescents. CONCLUSIONS: Self-reported measures of weight and height in adolescents do not present valid measures; therefore, they should not be used to replace measured values. Additionally, we observed that 10% of obese boys and 40% of obese girls could have remained unidentified if we had used only self-reported measures, emphasizing the effects of the low reliability of self-reporting.

Estimativa de valores corrigidos e o efeito da correção pelo erro de medida em dados dietéticos obtidos por Questionário de Frequência Alimentar para Adolescentes (QFAA)

The scope of this study was to estimate calibrated values for dietary data obtained by the Food Frequency Questionnaire for Adolescents (FFQA) and illustrate the effect of this approach on food consumption data. The adolescents were assessed on two occasions, with an average interval of twelve months. In 2004, 393 adolescents participated, and 289 were then reassessed in 2005. Dietary data obtained by the FFQA were calibrated using the regression coefficients estimated from the average of two 24-hour recalls (24HR) of the subsample. The calibrated values were similar to the the 24HR reference measurement in the subsample. In 2004 and 2005 a significant difference was observed between the average consumption levels of the FFQA before and after calibration for all nutrients. With the use of calibrated data the proportion of schoolchildren who had fiber intake below the recommended level increased. Therefore, it is seen that calibrated data can be used to obtain adjusted associations due to reclassification of subjects within the predetermined categories.