Boys from the poorest families in Australia are four times more likely to hit puberty early compared to their wealthiest counterparts, new research shows.
For girls from the same families it was twice as likely, and a researcher said it was probable this would also be the case in New Zealand.
The Murdoch Children's Research Institute in Melbourne tracked 3700 children and asked their parents to report on signs of puberty at age eight to nine, and again at age 10 to 11.
These included any growth spurts, pubic hair and skin changes, breast growth and menstruation in girls, and voice deepening and facial hair in boys.
They found that at 10-to-11-years-old, about 19 percent of all boys and 21 percent of all girls were classified in the early puberty group.
One of the researchers, pediatrician Melissa Wake, now works at Auckland University's Liggins Institute.
She said early puberty - at the age of 10 or 11 - could be one of the ways social disadvantage got under the skin of children and influenced their chances later in life, both in terms of economic prosperity and health.
While there was a clear link between early puberty and social disadvantage, the researchers did not determine why that was, she said.
But Dr Wake said early puberty could have a lasting impact.
"Puberty triggers really quite profound changes in children's brains and so children who go into puberty early are more likely to begin sexual experimentation and risky behaviours earlier than their peers.
"It's almost as if their brains aren't quite ready for it."
Dr Wake said it was likely the same link would be found in New Zealand children.