Abstract
Background: BMI is frequently used to evaluate obesity, but it is unable to assess fat distribution. Much attention has been given to abdominal fat measured by waist circumference (WC). Abdominal fat is a known risk factor for chronic diseases, but the impact of lung function among adolescents remains uncertain. Objective: To evaluate the association between WC and lung function parameters among adolescents. Methods: The original cohort comprised 5,249 hospital born children during the calendar year of 1993 in Pelotas, Brazil. In 2008-9, when participants were 15 years old, all cohort members were evaluated. WC was measured by trained interviewers and lung function tests were performed to obtain FVC and FEV1. Multiple linear regression models were performed and all analyses were stratified by sex. Results: 1,969 boys and 2,032 girls had data for spirometry and for WC. In the crude analyses we found a positive relationship between WC and FEV1 and FVC (liters) for both boys and girls. After adjusting for height, BMI, physical activity and wheezing in the past year, we found an inverse relationship between WC and FEV1 (β = -0.015 [95%CI -0.023; -0.008]), and FVC (β = -0.010 [95%CI -0.018; -0.001]) only for boys. For girls, the association was not significant. When we analyzed the predicted values, there was a significant association with WC (%FEV1, β = -0.413 [95%CI -0.619; -0.206]; %FVC β = -0.242 [95%CI -0.464; -0.020]) only for boys Conclusions: Increases in WC were associated with worse lung function parameters in Brazilian boys aged 15 years old. Improvement of lung health in adolescent can prevent lung diseases in adult life.