Early puberty linked to socio-economic status

Children from low socio-economic status backgrounds face much tougher health challenges, whether it be from stress, poor nutrition or lack of access to health services. But could it be that low-status itself can be enough to make a child sick in later life? The answer may be yes.

A major Australian study of almost 3,700 children has found that social and economic disadvantage can be a trigger for the early onset of puberty, putting disadvantaged children at higher risk of a host of associated future health problems.

The early onset of puberty has been linked to a higher risk of a various emotional, social problems from depression to substance abuse. But is also linked to diseases such as heart disease, stroke, and even cancers such as breast and prostate cancers.

The study, by the Murdoch Children’s Research Institute, found that boys from the lowest socio-economic households were four times more likely to hit puberty early and that girls from such disadvantaged households were almost twice as likely to hit puberty early.

The study controlled for a variety of other factors that are known to be associated with early onset puberty such as the child having been overweight, the puberty history of the parents, stress and premature birth. Despite that, the link to status was virtually unchanged. It means that early puberty may be one mechanism that underpins associations between early life disadvantage and poor health later.

“The results raise important questions over how social disadvantage might get under the skin,” says the study’s senior researcher, Professor George Patton of the MCRI and University’s of Melbourne’s Department of Paediatrics in the Faculty of Medicine, Dentistry and Health Sciences.

“It maybe that there are mechanisms that we don’t necessarily understand. For example it could be that a child’s perception of low status somehow translates into biological processes that then unlock the switch that keeps puberty at bay. We don’t know.”

Professor Patton speculates that such processes could be evolutionary. If a child is somehow aware of being low-status and that as a result the future may be difficult, the evolutionary programmed response could be to speed up sexual maturation so as to reproduce early.

“As a species, when social conditions are unfavourable, we may be programmed to accelerate the process of into puberty and reproductive maturity.”

The study has been published the journal of the American Academy of Pediatrics was based on children recruited to The Longitudinal Study of Australian Children (LSAC).

They assessed the puberty levels of children age 10-11 as observed by their parents. All those girls that had started menstruating automatically classified as having entered puberty early. Parents further reported on their child’s growth spurt, pubic hair and skin changes, as well as breast growth for girls and on facial hair and voice deepening for boys. In all, 21 per cent of girls and 19 per cent of boys were classified as being significantly early on the road to puberty.

In Australia girls on average start menstruating at around the age of 12-13, while the equivalent stage for boys, as could be measured by their voice breaking, is 13-14.

Socio-economic status was determined using LSAC indicators based on family income, education background, and occupational prestige.

They found that 40 per cent of the lowest status boys had entered puberty early, compared to only 12 per cent of the highest status boys. For the girls, 28 per cent of those from the lowest status group had entered puberty compared with 16 per cent among the highest status.

Professor Patton says the results are further evidence of the importance of addressing social and economic disadvantage in boosting health outcomes. “When aspiring to equal chance for health, you have to particularly promote opportunities for children from disadvantaged backgrounds,” Professor Patton says.

“We should in any case be looking at what we can do to increase the economic and social status of disadvantaged kids. This raises an additional question of whether by doing so, could we reduce rates of early puberty?”

The lead author on the study is Associate Professor Ying Sun, a visiting researcher at MCRI based at Anhui Medical University, China. The other co-authors are MCRI/Department of Pediatrics researchers Dr Fiona Mensah, Dr Peter Azzopardi, and Professor Melissa Wake.

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