Faster gains in weight, length or height, or body mass index in the first 5 years of life were associated with an earlier onset of puberty in boys and girls, based on data from a cohort study of more than 7,000 children.
In recent decades, clinicians and parents have raised concerns about an earlier onset of puberty in children in the United States and other countries, Izzudin M. Aris, PhD, of Harvard Medical School, Boston, and colleagues wrote.
“Children with earlier pubertal onset not only may be at increased risk for long-term chronic diseases, but also may experience adverse consequences during adolescence, including psychosocial difficulties and dysmetabolism,” they said. However, the effect of growth in the first 5 years of life on pubertal onset has not been well studied.
In a study published in JAMA Network Open, the researchers identified 7,495 children from 36 cohorts participating in the Environmental Influences on Child Health Outcomes program from Jan. 1, 1986, to Dec. 31, 2015.
The study population included 3,772 girls and 3,723 boys; 60% reported as White, 23% as Black, 15% as Hispanic, 12% as one of the following: American Indian or Alaska Native, Native Hawaiian or Pacific Islander, multiple races, or other race. Most (84.1%) were born during or after the year 2000.
The primary outcome was the pubertal growth spurt, also known as age at peak height velocity (APHV). The researchers measured growth at 3 age periods in the first 5 years (early infancy, late infancy, and early childhood) and estimated rates of weight, length or height, and body mass index (BMI) gain. Secondary outcomes included self-reported pubic hair staging and scores on the Pubertal Development Scale.
Overall, weight and length or height gain velocities declined in the first 5 years of life, and boys had faster gains in early infancy, compared with girls.
APHV was negatively correlated with puberty scores and Tanner staging for pubic hair development in both boys and girls, while puberty score was positively correlated with Tanner staging for pubic hair in both sexes.
After controlling for maternal and child confounders including maternal age at delivery, maternal education level, and year of birth, faster gains in weight, length or height, or BMI at each of the three measurement periods in early life was associated with earlier APHV in boys. No effect was noted for race, maternal education level, or birth year.
In girls, faster gains in weight, length, or height, only at the latest measurement period (early childhood) were associated with younger APHV. No associations with APHV occurred for velocities of BMI gain at any age period in girls, the researchers noted. However, age at menarche was positively correlated with early APHV and negatively correlated with puberty score and Tanner staging for pubic hair.
The findings support previous studies of associations between child growth and pubertal onset, the researchers wrote. The mechanisms of action are many, and have not been explained, the researchers wrote in their discussion of the findings.
“We speculate that insulinlike growth factor 1 may be a factor in the associations observed in the present study, either directly or indirectly through sex steroid synthesis and secretion. Alternatively, in girls, androgens and adipokines may be factors in the observed associations for pubic hair staging and menarche, respectively,” they said. Genetics and other factors including social factors, environmental exposures, diet, and physical activity also affect growth in early life.
The study findings were limited by several factors including the use of child-reported measures of pubic hair staging and parent reports of pubertal scores, with the potential for error and misclassification, the researchers noted. Other limitations include a lack of data on maternal age at menarche and the use of weight-for-length rather than BMI for children younger than 2 years.
However, the results were strengthened by the large sample size, long-term follow-up, and especially the use of a nationally representative contemporary cohort that addresses gaps in the current literature from later time periods. The results support the associations of sex-specific early pubertal onset in children with faster growth early in life. “In the long term, results of the present study may inform future research that aims to develop and/or test preventive interventions to optimize nutrition, environmental exposures, physical activity, and other behaviors related to growth during these age periods,” they concluded.