No Biological Father, High Income Spawns Early Puberty in Girls
Researchers find that some girls enter puberty early when no biological father is present in the home. The link was especially strong in African American households with absent fathers. The findings have scientists speculating as to the reasons, though several possibilities are suggested. Early puberty was also linked to just high income households.
Even after weight was taken into account, scientists still found the association between early signs of puberty among higher income households. According to lead author Julianna Deardorff, UC Berkeley assistant professor of maternal and child health, "While overweight and obesity alter the timing of girls' puberty, those factors don't explain all of the variance in pubertal timing".
The findings come from the Cohort study of Young Girls' Nutrition, Environment and Transitions (CYGNET). The purpose of the study is to measure the impact of early puberty on breast cancer development as well as other health outcomes later in life.
The research project is headed by Lawrence Kushi, associate director of etiology and prevention research at the Kaiser Permanente Northern California Division of Research, and part of UC San Francisco Bay Area Breast Cancer and the Environment Research Center (BCERC).
Reasons for early Puberty in the Absence of Biological Father not Clear
The CYGNET study is focused on environmental factors that contribute to early breast and pubic hair development, but Kushi says social and behavioral contexts are also of great interest, explaining the findings show "such factors may play important roles in the onset of puberty in girls." The reasons are not entirely clear. The researchers say the study brings more questions than answers.
The study participants were recruited through Kaiser Permanente, followed annually for two years, and included 444 girls ages 6-8. Past studies examined onset of menses as a gauge of early puberty, but there have been no studies regarding income, ethnicity, and body mass index. The new analysis takes into account signs of puberty prior to menarche. Researchers interviewed caregivers, collecting data about other residents in the home and their relationship to the girls studied.
Of the 444 girls, 80 had absent biological fathers. In households of $50,000 annually or more, the researchers noted early breast and public hair development. For African American, early puberty particularly occurred in association with higher income.
Several reasons for the findings have been suggested that include unstable family environment, exposure to pheromones of unrelated males and exposure to more artificial light from computers and other technologies - findings also found in animal studies. It might be possible that African-American girls reach puberty early from exposure to estrogen stimulating beauty products.
Bay Area BCERC's principal investigator Dr. Robert Hiatt, UCSF professor and co-chair of epidemiology and biostatistics, and director of population science at the campus's Helen Diller Family Comprehensive Cancer Center says the findings are important to women's health, "since girls who enter puberty earlier than their peers are not only at greater risk for reproductive cancers, they are also more likely to develop asthma and engage in higher risk sexual behaviors and substance abuse".
No one knows why girls in the United States are reaching puberty so early. A study published last month by BCERC researchers at Cincinnati Children's Hospital Medical Center that included 1200 girls showed breast development in 15 percent of the participants by age 7 - an increase from 1990 findings.