A study conducted by researchers at UC Berkeley School of Public Health, UCSF and Kaiser Permanente Northern California, or KPNC, has found a strong association between early onset puberty and young women born into neighborhoods of less racial and economic privilege.

The study, administered by KPNC, was part of the larger KPNC Puberty Study. It aimed to identify life risk variables correlated with early puberty among young adults, mainly because of an observed increase of children with earlier pubertal onset in the last few decades.

“Our findings revealed that neighborhood racial and economic privilege are strongly associated with the timing of girls’ puberty,” Kubo said in an email. “Compared to girls born into neighborhoods of concentrated privilege, girls born into neighborhoods of concentrated disadvantage were significantly more likely to experience pubarche and thelarche at earlier ages.”

The main researchers for the study were lead authors Julia Acker, a doctoral student in epidemiology at UC Berkeley School of Public Health, and Mahasin Mujahid, the epidemiology division chair, as well as co-senior authors Julianna Deardorff, the Associate Dean at UC Berkeley School of Public Health, and Ai Kubo, the principal investigator of the study and a epidemiologist at KPNC.

Kubo said the larger cohort puberty study sampled over 100,000 KPNC adolescents, with over 46,000 girls from over 2,500 neighborhoods in northern California born at a KPNC facility between 2005 to 2011. KPNC pediatricians evaluated pubertal timing through routine check-ups beginning at the age of six, measuring two main factors: pubic hair onset and breast development onset.

Within the study, researchers relied on Harvard School of Public Health doctor Nancy Krieger’s “Index of Concentration at the Extremes” as the standard to assess the amount of neighborhood racial and economic privilege.

The metric uses U.S. Census data to measure an estimated concentration of white, high-income residents proportioned to black, low-income residents in a single neighborhood, deeming neighborhoods with the majority being white, wealthy individuals to be those with more racial and economic privilege.

Kubo notes that previous research on early onset puberty in young adults has singled out variables based on individual factors as correlating with racial and ethnic differences, such as obesity and race alone, while this study links neighborhood condition disparities shaped by “racially discriminatory practices and policies” to the racial and ethnic differences instead.

For future research, the team intends to explore more neighborhood condition constants, including population density and ethnic enclave, along with early life variables such as maternal mental health, exposure to intrauterine or secondhand smoking and disadvantageous childhood events.

“Overall, our findings suggest that policies designed to improve economic opportunity and conditions in racially segregated, economically vulnerable neighborhoods have the potential to reduce disparities in early pubertal timing affecting racially marginalized girls,” Kubo said in the email.