SNIPPETS - High altitude living linked to higher SIDS risk

High altitude living linked to higher SIDS risk

Living at high altitude is associated with increased risk of sudden infant death syndrome (SIDS), a new report has found. Researchers studied Colorado birth certificate and death registries from 2007 to 2012, and assessed the link to altitude using maternal residential addresses for nearly 3,95,000 infants.

The findings were published in Pediatrics. After controlling for maternal age and education, infant weight, cigarette smoking and other factors, and given the effect of the Back to Sleep campaign, which started in 1994 and encouraged parents to lay babies on their backs, the researchers found that infants who lived above 8,000 feet had twice the risk of SIDS compared with those who lived below 6,000 feet.
But “despite the doubling of risk,” said Dr David F Katz, a cardiologist at the university of Colorado and the study’s lead author, “the absolute risk remains very low.” Expectant or new parents residing at high altitude should not move to sea level, the authors wrote.

But “this is a call for people living in high altitudes to be very vigilant” about other factors that may lower SIDS risk, “like putting the baby on his back every time, no smoking, encourage breast-feeding,” said Dr Amber Khanna, a cardiologist and pediatrician at the University of Colorado and the study’s senior author. The baby also should sleep in a crib without any bumpers or blankets, she said. The authors suggested that it could be that more babies at high altitudes have abnormally low oxygen levels that may somehow contribute to SIDS.

“I’m afraid people will interpret this study as saying high altitudes are dangerous, but this association really begs for further research into why it exists,” David said.
Catherine Saint Louis

----------------------------------------------------------------------------------

The upper crust in a tectonic plate collision
The recent earthquakes in Nepal made me wonder: When tectonic plates collide, what determines which one winds up on top?

“The short answer is buoyancy,” said Colin P Stark, an associate research
professor at the Lamont-Doherty Earth Observatory of Columbia University. Oceanic plates and continental plates have different levels of buoyancy, he said, and when they collide, the continental plate comes out on top. Earth is losing heat to space, Colin said.

“This heat loss has created a cold, rigid skin called the lithosphere, a fancy name for the layer that forms the tectonic plates,” he said. The lithosphere, which is about 62 miles thick, lies above and slides over mantle rocks, which are warmer and weaker and flow slowly as they transfer heat from the core, about 1,865 miles below. The mantle is fluid-like but not liquid, Colin said.

The lithosphere grows colder and denser over time, Colin said. An oceanic plate thus eventually becomes less buoyant than the mantle below, so it sinks, dragging the rest of the plate sideways and down.

This begins a process of collision with the adjacent plate, a phenomenon called subduction. Continental plates have a thicker crustal layer made of lighter rocks than those found in oceanic plates. Even as they cool, they remain more buoyant than the fluid-like mantle below, and they float on top.

Thus, when a continental plate collides with an oceanic plate, the less buoyant oceanic plate sinks and slides under the continental plate, Colin said. “Back in the Cretaceous, there was an ocean called Tethys between the two continental plates of India and Nepal-Tibet,” Stark said.

“The Tethyan oceanic plate started to sink and then slide under Nepal. India was dragged northward, and about 40 to 50 million years ago, the two continental plates collided. Since Tethys was already sliding under Nepal, India followed. As a result, Nepal ended up on top.”

----------------------------------------------------------------------------------