What Influences Earlier Puberty? The Role of the Urban Environment and Early-life Nutrition

Early-life exposure to air pollution, urban environments, natural spaces, and breastfeeding may influence the timing of puberty, according to new research.

[This article was co-authored by Marta Pinto da Costa and Augusto Anguita-Ruiz, Junior Research Leader at ISGlobal.]

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Over the past decades, a worldwide declining tendency in the age at menarche and the onset of puberty has been observed. Although genetic factors have been described as the main determinants of pubertal timing, a growing body of evidence suggest that children’s early-life environmental exposures and lifestyle may also influence this biological process. Understanding these potentially modifiable risk factors is important, as earlier pubertal timing has been linked to several adverse health outcomes, including an increased risk of metabolic disorders, cardiovascular disease, and breast and other reproductive cancers. Earlier pubertal timing therefore represents an important public health concern.

Researchers at ISGlobal and at the Insitute of Public Health of the University of Porto (Portugal) are currently exploring how children’s early-life living environments and early life nutrition may influence pubertal timing, using data from to European birth cohorts: the Portuguese population-based birth cohort Generation XXI and the Spanish INMA Project. Both cohorts have followed thousands of children from pregnancy into adolescence, collecting detailed data on health status, sociodemographic characteristics, living environments and lifestyle factors.

How Was the Study Conducted?

In the present study, the researchers focused on early-life urban environmental exposures, including air pollution, traffic, built environment and natural spaces, measured from pregnancy through early childhood. Rather than focus on a single exposure in isolation, an exposome approach was adopted, allowing the researchers to consider how multiple exposures coexist and their potential combined influence on pubertal timing. Exclusive breastfeeding duration and childhood diet quality were also considered. Pubertal timing was assessed at 9-10 years of age through clinical Tanner staging and/or parental report of the child’s pubertal status based on the Pubertal Development Scale (PDS). Girls also reported their age at menarche during later follow-ups.

Breastfeeding and Pubertal Development

Early-life nutrition seems to play a role on pubertal timing. A longer exclusive breastfeeding duration was associated with less advanced pubertal development among girls. This finding aligns with previous evidence suggesting that breastfeeding may have a potential protective role against earlier pubertal onset. In contrast, childhood diet quality was not associated with pubertal development in this study.

Traffic and Air Pollution: The Strongest Associations

Preliminary results also suggest that early-life urban environmental exposures may play a role in shaping pubertal timing. Children living in less favourable urban environments, mainly characterised by higher building and population density, heavier traffic and higher levels of air pollution, together with lower access to natural spaces, tended to show signs of more advanced pubertal development and age at menarche.

Exposure patterns related to traffic and air pollution emerged as the most consistently associated with earlier puberty-related outcomes

In particular, exposure patterns related to traffic and air pollution emerged as the most consistently associated with earlier puberty-related outcomes. Urban air pollution is a complex mixture of particles and chemicals, some of which are known to interfere with endocrine pathways involved in growth and reproductive development.

For instance, epidemiological studies suggest that Particulate Matter (PM) may influence estrogen-related signalling pathways, which may play a key role on the release of kisspeptin and subsequently trigger gonadotropin-releasing hormone secretion, a central regulator of pubertal onset.

The Potential Protective Role of Green and Blue Spaces

In addition, access to natural spaces also appeared to be relevant. Children growing up in areas with less surrounding green and blue spaces tended to show more advanced pubertal development in some analyses. Natural environments may help reduce stress and promote physical activity, both of which have been linked to hormonal regulation and child development.

Access to natural spaces also appeared to be relevant. Children growing up in areas with less surrounding green and blue spaces tended to show more advanced pubertal development in some analyses

Early childhood appears to be a sensitive period for pubertal development, since exposures occurring during pregnancy and early childhood may have later consequences for biological development. From a public health perspective, these findings represent an important step towards understanding how combinations of environmental and lifestyle factors in early life may shape pubertal timing, and suggest that improving air quality, reducing traffic-related pollution, increasing access to natural spaces, and promoting longer durations of exclusive breastfeeding may contribute to more favourable developmental outcomes for future generations.