Puberty starting earlier in American kids – Does growth from 0-5 years play a role?

Izzuddin Aris, PhD

​As adults, we can all look back on the physical, emotional, and social changes during puberty that can be a roller coaster for children to navigate. Puberty is a key stage during child development; it’s the period when male and female children become sexually mature and typically occurs between ages 10-14 for girls and ages 12-16 for boys. However, previous research has indicated that children in the United States are entering puberty at younger ages and that these children may be at higher risk of developing certain diseases, such as type 2 diabetes, later in life. A better understanding of how early life factors affect puberty development is important for combating earlier puberty onset.

Prior research has pointed to an association between prepubertal body mass index (BMI) and timing of puberty, with higher BMI in childhood associated with earlier pubertal onset. Faster growth may alter the early hormonal environment and program the age of puberty onset and rate of progression through puberty. To date, the extent to which growth in the first five years of life – a critical developmental life stage that lays the foundation for long-term health outcomes – is associated with pubertal onset remains understudied due to few prospective studies have yielded data on growth measures across distinct age periods in the first few years of life and even fewer have ascertained sensitive age periods during which early-life growth may be associated with pubertal onset.

To address these gaps, we leveraged existing data on the weight, height, and signs of puberty during the first five years of life from nearly 7,500 children within 36 birth cohorts from the National Institutes of Health (NIH) Environmental Influences on Child Health Outcomes (ECHO) Program. The ECHO Program includes a large collaborative consortium consisting of 69 existing and ongoing cohorts that investigate how environmental exposures in early life, including physical, chemical, social, behavioral, biological, natural, and built environments, affect child health and development. We examined signs of puberty: age when the child experienced the most growth due to puberty; age at the time of their first period (in female children only); puberty development score; and pubic hair development. We then examined how gains in weight, height, and body mass index at different stages between birth and age 5 were related to puberty development, controlling for maternal and child characteristics.
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Our results showed that male children who gained weight or grew faster than their peers in the first five years of life were associated with entering puberty at a younger age. For female children, similar results were seen for those with faster weight gains, but not for faster linear growth. Female children with faster weight gains during infancy (6 months to 2 years of age) or early childhood (2 to 5 years of age) started their periods earlier and had more advanced pubic hair development.
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Taken together, these findings suggest that there are sex-specific associations between faster growth in early life and earlier pubertal onset. These key findings have a direct clinical impact; as pediatricians regularly measure weight and height during routine visits and use growth curves to identify abnormal growth predictions, they could closely monitor children who have faster growth in the first five years of life for earlier onset of puberty. The study results may also inform future studies that aim to develop or test interventions (e.g., good nutrition, increased physical activity, and/or other behaviors related to growth during the first five years of life) to help prevent earlier onset of puberty, which is important given that an earlier onset of puberty is linked with poorer health outcomes later in life.