Obesity may delay puberty in boys

BY: Paul Taylor, The Globe and Mail

The obesity epidemic may be producing a generation of late-blooming males.

Overweight boys tend to start puberty at a later age than their less-heavy peers, according to one of the first studies to chart the effects of childhood obesity on male sexual development.

Previous studies have focused primarily on girls – and came to an opposite conclusion. "Heavier girls tend to develop earlier, rather than later," said the lead author of the new study, Joyce Lee of C.S. Mott Children's Hospital in Ann Arbor, Mich.

Dr. Lee and her research colleagues aren't sure why excess weight seems to speed up the sexual maturation process in females while slowing it down in males. But one thing is obvious: "This tells us that boys and girls are truly different and there is a lot we don't understand about the hormonal mechanism governing puberty," Dr. Lee said.

For their study, the researchers analyzed data on 401 boys from diverse socioeconomic backgrounds from across the United States. Their growth and development was regularly measured between 2 and 12 years of age.

Puberty is a multistaged process lasting three to five years. About half of boys start going through a period of penis and testicular growth at roughly age 10, Dr. Lee said. But many of the overweight boys in the study still showed no genital changes by 11½ years of age, according to the findings published in the journal Archives of Pediatric & Adolescent Medicine.

Dr. Lee noted that fat is biologically active and can influence the level of certain hormones circulating in the body.

One possibility is that substances released by the fat act to convert the male hormone androgen into the female hormone estrogen, which could possibly hasten puberty in girls but delay it in boys.

But Dr. Lee stressed that more studies must be conducted before researchers have answers.

What's also uncertain is the long-term health and emotional consequences of having an altered sexual development.

"I think we can say that obesity is a stigma in itself, and when you add on to the teenage boy the fact that he is not developing like his peers, it is another stigma that could cause anxiety for the child and the parents."

The riddle of SIDS

U.S. researchers have moved one step closer to solving the mystery of sudden infant death syndrome, which claims the lives of seemingly healthy babies while they sleep.

The new work revealed that the brainstems of these babies had lower than normal levels of serotonin, a chemical that transmits messages between nerve cells.

Earlier research had already indicated there was a serotonin problem, but scientists weren't sure if there was too little or too much of the chemical. "We now know there is a deficit of serotonin," said one of the authors of the new study, David Paterson of Children's Hospital Boston.

The findings, published in the Journal of the American Medical Association, are based on a comparison of tissue samples from the autopsies of 41 infants who succumbed to SIDS and 12 who died of other causes.

The brainstem, in combination with serotonin, helps to regulate basic functions such as body temperature, blood pressure, heart rate as well as breathing.

The researchers believe that a low amount of serotonin may inhibit an infant's ability to respond to breathing challenges, such as inappropriate oxygen and carbon dioxide levels.

"The baby experiences some kind of stress during sleep, such as rebreathing carbon dioxide in the face-down position or increased temperature from over bundling, that cannot be compensated for by the defective brainstem circuits, and the baby then goes on to die," the lead researcher, Hannah Kinney, speculated in a statement.

"In a normal baby rebreathing carbon dioxide, serotonin pathways in the brainstem would stir the baby awake long enough to turn its head, allowing it to breathe fresh air," she added. A baby with low serotonin levels in the brainstem may never stir.

Dr. Paterson said if their hunch is correct, the researchers may be able to develop a diagnostic test to identify children born with the serotonin defect. But, he cautioned, it could take years before doctors can accurately pinpoint high-risk infants. In the meantime, he said it's critically important for all parents to adhere to the safety recommendations known to reduce the risk of SIDS – such as putting babies to sleep on their backs and not their bellies.

Survival of the fittest

New immigrants are at a lower risk of suffering from a stroke than long-term residents of Canada, according to a study by researchers at the Institute for Clinical Evaluative Sciences and St. Michael's Hospital in Toronto.

"We were surprised by our findings," said the lead researcher, Gustavo Saposnik, a St. Mike's neurologist. He noted that immigrants face many stresses that, in theory, should put added pressures on their health and boost their odds of having a stroke.

For the study, the researchers identified all new immigrants to Ontario over a 12-year period and compared them with people of the same age and gender who were existing residents of the province. The health of the new arrivals was charted for six years. In that time, the recent immigrants had a 30 per cent lower risk of stroke than long-term residents, according to the findings published in the journal Neurology.

So why the lower stroke risk among new immigrants? Dr. Saposnik now believes that people who are able to make it through the immigration process tend to be in generally good health, which helps them cope with the added pressures of adjusting to a new homeland.

"New immigrants definitely don't appear to be a burden in terms of health care – at least for the first six years," he said.

Of course, he added, there is always the possibility that the health of immigrants could slip over time if they adopt a lot of unhealthy North American habits – such as overeating and insufficient exercise.