Pubertal timing and tempo and body mass index trajectories: investigating the confounding role of childhood body mass index.

Earlier pubertal timing and faster pubertal tempo (pace of progression through puberty) might be associated with increased body mass index (BMI) later in life. In a follow-up study of 13 219 boys and girls from the Danish National Birth Cohort, we investigated the association between pubertal timing and tempo and BMI trajectories from puberty to adulthood and explored the potential confounding role of childhood BMI. Based on half-yearly information on self-reported current Tanner stages, pubertal timing and tempo were estimated using nonlinear mixed-effect growth models. In total, 136 457 height and weight measurements from 7 to 18 years were included. BMI trajectories from 11 to 18 years were fitted according to pubertal timing and tempo while adjusting for potential confounders, including childhood BMI at age 7 years. Children with earlier pubertal timing had higher and children with later pubertal timing had lower BMI trajectories from 11 to 18 years than children with average pubertal timing. After adjustment for childhood BMI, the difference disappeared in boys but persisted in girls, suggesting that earlier pubertal timing may be independently associated with later BMI in girls only. Faster pubertal tempo was associated with slightly higher BMI in young women only.