Early drinking and smoking might delay onset of puberty in girls, a new study has found.
Puberty can start as early as age 7 or 8, but most girls start to develop breasts, the first sign of sexual development, between ages 9 and 13.
Late puberty in girls can have wide ranging health effects. When puberty begins past age 13, girls might not grow as tall and their bones might not become as strong.
Previous animal studies have shown that exposure to alcohol and tobacco can affect hormone levels, which in turn can delay sexual development.
However, researchers have not investigated the association extensively in humans or in young girls specifically.
For the new study Jennifer Peck, Ph.D. and her colleagues at the University of Oklahoma Health Sciences Center in Oklahoma City used data from previously conducted interviews with 3,106 girls between ages 11 and 21.
The girls were asked about when they started using alcohol and tobacco and the age at which they first noticed signs of sexual development.
Less than 3 percent of the girls reported alcohol or tobacco use at early ages, but those girls were likely to notice signs of puberty later than the girls who had not reported early alcohol or tobacco use.
"What catches the eye in the study - the strongest association we observed - was that girls who reported pre-pubertal alcohol use had four times the odds of late breast development compared to girls who did not use alcohol," Peck said.
The study appears online in the Journal of Adolescent Health.