Sedentary behavior and physical activity are independently associated with obesity in Brazilian adolescents: a quantile regression analysis

Camilo Luis Monteiro Lourenço,Edmar Lacerda Mendes

doi:10.21527/2176-7114.2021.44.10337

Camilo Luis Monteiro Lourenço, Edmar Lacerda Mendes

Open Access

https://doi.org/10.21527/2176-7114.2021.44.10337

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Abstract

Objective: to test the association of SB and moderate to vigorous physical activity (MVPA) with body mass index (BMI) in a representative sample of Brazilian young people. Methods: This is a cross-sectional school-based study (n = 1,023), including adolescents (14-21y; 54% female) from public and private schools in a Brazilian city. The survey was conducted in 2015 and the adolescents self-reported SB (screen time) and MVPA. Height and body mass were measured to calculate BMI. Quantile regression was used to investigate the association between SB, MVPA and BMI distribution percentiles (P10 ..., P90; statistical significance p <.01). Results: SB and MVPA were associated with higher and lower BMI values, respectively. Quantile regression revealed that the associations were nonlinear and stronger in the upper BMI percentiles. Also, in the adjusted models (SB and MVPA in the same model), the associations were enhanced for MVPA. For example, each additional hour of MVPA at P10 was associated with −0.05 (p <.01) lower BMI value, against −0.09 at P50 (p <.01) and even lower at P90, −0.24 (p <.01). Conclusion: SB and MVPA were independently and nonlinearly associated with BMI in our sample of Brazilian youth. The associations were more notable in the higher percentiles of the BMI distribution. Our findings suggest that nonlinearity between exposures and outcome should be considered when proposing future strategies for pediatric obesity prevention.

Highlights

It is estimated that one in four Latin American adolescents is overweight,[1] over 50% of Brazilian adolescents have excessive sedentary behavior (SB)[2] and 84% do not of them meet recommendations of moderate to vigorous physical activity (MVPA).[3]
The median time spent on SB was 5.9 hours per day while the median time spent on MVPA was 68.9 minutes per day
The results showed that a longer time spent on MVPA was independently associated with lower body mass index (BMI) values

Summary

Introduction

It is estimated that one in four Latin American adolescents is overweight,[1] over 50% of Brazilian adolescents have excessive sedentary behavior (SB)[2] and 84% do not of them meet recommendations of moderate to vigorous physical activity (MVPA).[3]. The statistical methods used to investigate the association between SB, MVPA, and pediatric obesity are mostly applied with logistic models (categorized outcome) or reduced to means (ordinary linear regression). These models may fail to reveal important information. Ordinary linear regression fails to present the results of the association between SB and higher percentiles (90th percentile) of the body mass index (BMI) distribution. Quantile regression, which is a regression method aimed at estimating either the conditional median or other quantiles of a continuous variable[6], has the advantage of exploring how predictors (e.g. SB and MVPA) impact the shape of the distribution of a continuous variable (e.g. BMI)

Objectives

Methods

Results