Is the secular trend in height delaying overweight rise among adolescents? the Brazilian case

Abstract

Objective To explore if the secular trend in height is contributing to delay overweight rise among Brazilian adolescents. Design Changes in BMI mean over time were fitted using linear regression including as independent variables survey year, height, survey-specific income quintiles, age and an interaction term of height × survey year. Overweight was defined as BMI≥25·0 kg/m2. Changes in overweight prevalence over time were fitted using Poisson regression. Setting Four national household surveys: 1974/5, 1989, 2002/3 and 2008/9. Subjects Brazilian adolescents. Results Mean values of height and BMI increased over the period, for both sexes and in all age ranges, except for girls aged 14-19 years from 1989 to 2002/3. The highest average increment and mean rate of height were between 1989 and 2002/3 and in 10-15-year-olds. The annual increment of height decreased from 2002/3 to 2008/9 in parallel with the increment in BMI rate. After fitting the regression model, the height × survey year interaction and per capita income were strong vectors to increase BMI mean. Changes in increment rate of height played a protective role against overweight in the last two periods for both sexes, mainly for girls. The period from 1989 to 2002/3 was the strongest vector associated with overweight in boys and the association decreased to the next period, from 2002/3 to 2008/9. Conclusions BMI and height of adolescents have increased in a wavering and alternate way throughout four decades in Brazil. The rate of height increment has played a protective role against overweight in adolescents.