Your Birth Date Is Arbitrary — It's Your Biological Age That Matters

Though your chronological age records the passage of time, your biological age records what’s happening inside you.

In a study published in the journal Molecular Cell, researchers discovered rapid aging in HIV patients. Biologist Trey Ideker and his team at the University of California, San Diego made this discovery, finding that these patients were susceptible to age-related diseases such as osteoporosis, heart disease, and dementia five years earlier than their non-infected peers. Researchers aren’t sure whether it is anti-retroviral drug treatments or the virus itself that causes this. But some aspect seems to speed up their biological age. So what is one’s biological age, and how is it different from the chronological kind?


Our biological age is how our bodily tissues, systems, and organs grow older. Put another way, it is how close or far away our organs are from age-related conditions. One’s biological age is a far better indicator of their health than their age in years. This is usually determined by looking at a person’s genetic code. There can be dramatic discrepancies, such as one being a full decade older or younger biologically, than they are chronologically. One thing geneticists look at is telomeres. These reside at the ends of chromosomes. They protect the ends from fusion with other chromosomes and from deterioration. Telomeres affect how long cells live and when they die.

A telomere’s length helps determine when a cell meets its end. A bead falls off the end of a chromosome every time a cell divides. The longer one lives in years, the shorter the length of their telomeres. Those with telomerase mutations or shorter telomeres are more likely to die early, either by developing a neurodegenerative disorder such as Alzheimer’s or from a serious illness. Researchers aren’t sure, but some evidence suggests that leading a healthy lifestyle may help to maintain the length of telomeres. 

Another important indicator is methylation of DNA. This has to do with epigenetics, or adaptations to the environment which are then written into our genes. Methylation are labels that tell cells whether they should lock genes in the on or off position. Pivotal for the developing embryo, methylation aids in the process of cell differentiation. This is the reason why a heart cell and brain cell can be coded the same but function differently.

A chromosome with telomeres in red.

In 2013, UCLA geneticist Steve Horvath decided he wanted to see if methylation could predict a person’s age using tissue and cell samples. The idea was to determine one’s biological age and in that, their susceptibility to age-related diseases. He took 8,000 samples from 51 different kinds of cells and tissues. Soon, Horvath discovered that one’s chronological age was often very different from their biological one.

Not all organs in one’s body age the same age. Some grow older more quickly than others. Women will be saddened to know that breast tissue is one of the most mature parts of the human body. A woman’s breasts can actually be up to three years older than the rest of her. Breast cancer is so prevalent, and Horvath believes that biological age has something to do with it. If cancer tissue is present, the adjacent healthy breast tissue will be about 12 years older than a woman’s chronological age, or more. Horvath believes these insights will lead to better diagnostics and treatment options for breast cancer, among other diseases.

DNA methylation

In another experiment, Horvath took tissue samples from childhood cancer patients. Some brain cancer samples were found to have a biological age of 80 years. For some good news, human heart tissue was found to be younger than many others in the body. Stem cells are often recruited to help create new cardiac muscle, knowledge that someday may help us combat cardiovascular disease in an entirely new way.

Another study looked at the elderly and their biological age. Those who had poor functioning were found to be biologically older, while those with better functioning were biologically younger. Now with Horvath’s studies in hand, researchers can look into what pathways biological aging takes, and discover new entry points and therapies to treat age-related diseases. Researchers might even find a way to undo aging itself. According to Horvath, "The big question is whether the biological clock controls a process that leads to aging. If so, the clock will become an important biomarker for studying new therapeutic approaches to keeping us young."

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Why "nuclear pasta" is the strongest material in the universe

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Accretion disk surrounding a neutron star. Credit: NASA
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Superman is known as the "Man of Steel" for his strength and indestructibility. But the discovery of a new material that's 10 billion times harder to break than steel begs the question—is it time for a new superhero known as "Nuclear Pasta"? That's the name of the substance that a team of researchers thinks is the strongest known material in the universe.

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The competition between forces from protons and neutrons inside a neutron star create super-dense shapes that look like long cylinders or flat planes, referred to as "spaghetti" and "lasagna," respectively. That's also where we get the overall name of nuclear pasta.

Caplan & Horowitz/arXiv

Diagrams illustrating the different types of so-called nuclear pasta.

The researchers' computer simulations needed 2 million hours of processor time before completion, which would be, according to a press release from McGill University, "the equivalent of 250 years on a laptop with a single good GPU." Fortunately, the researchers had access to a supercomputer, although it still took a couple of years. The scientists' simulations consisted of stretching and deforming the nuclear pasta to see how it behaved and what it would take to break it.

While they were able to discover just how strong nuclear pasta seems to be, no one is holding their breath that we'll be sending out missions to mine this substance any time soon. Instead, the discovery has other significant applications.

One of the study's co-authors, Matthew Caplan, a postdoctoral research fellow at McGill University, said the neutron stars would be "a hundred trillion times denser than anything on earth." Understanding what's inside them would be valuable for astronomers because now only the outer layer of such starts can be observed.

"A lot of interesting physics is going on here under extreme conditions and so understanding the physical properties of a neutron star is a way for scientists to test their theories and models," Caplan added. "With this result, many problems need to be revisited. How large a mountain can you build on a neutron star before the crust breaks and it collapses? What will it look like? And most importantly, how can astronomers observe it?"

Another possibility worth studying is that, due to its instability, nuclear pasta might generate gravitational waves. It may be possible to observe them at some point here on Earth by utilizing very sensitive equipment.

The team of scientists also included A. S. Schneider from California Institute of Technology and C. J. Horowitz from Indiana University.

Check out the study "The elasticity of nuclear pasta," published in Physical Review Letters.


How a huge, underwater wall could save melting Antarctic glaciers

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Image: NASA
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An "unthinkable" engineering project

"If [glacial geoengineering] works there then we would expect it to work on less challenging glaciers as well," the authors wrote in the study.

One approach involves using sand or gravel to build artificial mounds on the seafloor that would help support the glacier and hopefully allow it to regrow. In another strategy, an underwater wall would be built to prevent warm waters from eating away at the glacier's base.

The most effective design, according to the team's computer simulations, would be a miles-long and very tall wall, or "artificial sill," that serves as a "continuous barrier" across the length of the glacier, providing it both physical support and protection from warm waters. Although the study authors suggested this option is currently beyond any engineering feat humans have attempted, it was shown to be the most effective solution in preventing the glacier from collapsing.

Source: Wolovick et al.

An example of the proposed geoengineering project. By blocking off the warm water that would otherwise eat away at the glacier's base, further sea level rise might be preventable.

But other, more feasible options could also be effective. For example, building a smaller wall that blocks about 50% of warm water from reaching the glacier would have about a 70% chance of preventing a runaway collapse, while constructing a series of isolated, 1,000-foot-tall columns on the seafloor as supports had about a 30% chance of success.

Still, the authors note that the frigid waters of the Antarctica present unprecedently challenging conditions for such an ambitious geoengineering project. They were also sure to caution that their encouraging results shouldn't be seen as reasons to neglect other measures that would cut global emissions or otherwise combat climate change.

"There are dishonest elements of society that will try to use our research to argue against the necessity of emissions' reductions. Our research does not in any way support that interpretation," they wrote.

"The more carbon we emit, the less likely it becomes that the ice sheets will survive in the long term at anything close to their present volume."

A 2015 report from the National Academies of Sciences, Engineering, and Medicine illustrates the potentially devastating effects of ice-shelf melting in western Antarctica.

"As the oceans and atmosphere warm, melting of ice shelves in key areas around the edges of the Antarctic ice sheet could trigger a runaway collapse process known as Marine Ice Sheet Instability. If this were to occur, the collapse of the West Antarctic Ice Sheet (WAIS) could potentially contribute 2 to 4 meters (6.5 to 13 feet) of global sea level rise within just a few centuries."