FRIDAY, Sept. 17 (HealthDay News) -- Girls growing up in
higher-income homes without a biological father are likely to reach
puberty earlier than others, new research finds.
"In higher-income families, father absence predicted earlier puberty, but it did not in lower-income, father-absent [households]," said study leader Julianna Deardorff.
"Girls in upper-income households without a father were at least twice as likely to experience early onset of puberty, as demonstrated by breast development," she said. The researchers defined higher income as $50,000 or more a year.
Early maturation in girls is linked with emotional and substance
use problems and earlier sexual activity. These girls also face a
higher risk for breast cancer and other reproductive cancers later
Previous research has linked absent-father households and
earlier puberty, but this study adds more information, said
Deardorff, an assistant professor of public health at the
University of California, Berkeley.
"We were looking at very early signs," such as breast development and the growth of pubic hair, she said. Other researchers have focused on the start of menstruation without looking at factors such as income and ethnicity, according to background information in the study.
Girls are reaching puberty earlier in the United States, where
the average age of menstruation is about 12 years, Deardorff said.
Recent research has found some girls starting to develop breasts as
early as age 7 or 8.
For their study, published Sept. 17 in the
Journal of Adolescent Health, Deardorff and her colleagues followed 444 girls, aged 6 to 8 at the start, and their mothers. They gathered extensive data on factors such as weight, height, stage of breast and pubic hair development, father's presence and income. Eighty of the girls said their fathers did not live with them.
After two years of follow-up, the researchers saw earlier breast
development in higher-income girls in absentee-dad homes across the
board, but noted earlier pubic hair growth only in black girls from
richer families. Having another male, such as a stepfather, in the
home didn't change the findings.
They also found, as other researchers have, that higher
body-mass index (BMI), a calculation based on height and weight,
was also linked with earlier puberty.
The authors said they can only speculate on the reasons behind
the connections. Exposure to more artificial light from TVs or
computers is one theory. Other possibilities include weak maternal
bonding, assuming a single mother is working long hours, or contact
with chemicals that may have estrogenic effects -- perhaps hair
straighteners in the case of black preteens.
"It's possible girls in those homes are exposed to different environmental exposures, for example, toxins," Deardorff said. They may be exposed more to cosmetics and other personal care products, for instance, and some experts have expressed concerns about what they see as hormone-disrupting chemicals in those products.
Anthony Bogaert, a professor of community health sciences at
Brock University in St. Catharines, Canada, reported a link between
absent fathers and early puberty in boys and girls in in 2005 in
Journal of Adolescence.
Looking at a national sample, he found that those who had had an
absent father at 14 had likely had an early age of puberty. For his
study, he defined puberty for girls as the onset of menstruation
and for boys, voice change.
"It is difficult to know why this relationship occurs -- for example, stress, genes -- so more work needs to be conducted on the exact mechanism underlying it," he said. This new study is an "interesting" addition to the literature on the topic, he said.
How can parents in father-absent homes compensate, if at
Until researchers determine the cause of the connection, Bogaert
said it's premature to offer suggestions.
Deardorff suggested focusing on other links, such as the higher
BMI and its association with earlier puberty.
"Probably one of the primary targets is going to be body weight and physical activity [to maintain a healthy weight]," she said.
To learn more about puberty, visit the
American Academy of Pediatrics.