Issue 62

The odds of accidental deaths, no pain in the brain, and bacterial henchmen

Jan. 26, 2019

Hello friend! Welcome to Scrap Facts.

I'm a reporter covering health and science with insatiable curiosity. I love everything I learn, not all of which gets its own story. Each week, I'll bring you some of my favorite facts that I picked up on the job or while out living life.

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In the US, your odds of dying in a gun assault are higher than your odds of dying by being hit by a car.

Found while reporting: The death rate for opioid use has surpassed car crashes in the US.

The news from the 2018 US National Safety Council’s annual report on preventable deaths in the US wasn’t great. In general, the number of preventable deaths went up by more than 5% from 2016 to 2017, bringing the total to 169,936.

I wrote about how deaths related to opioids specifically had surpassed deaths related to car crashes, but equally compelling are the odds of dying at the hands of gun violence compared to pedestrian deaths. A person born in 2017 has a 1 in 285 chance of being fatally shot, and a 1 in 556 chance of dying by being hit by a car while walking.

Equally worrying? That same person born in 2017 in the US has a 1 in 88 chance of taking their own life.

We know that cars are dangerous, but the vast majority of us consider it to be an acceptable risk get to work and back home again (David Spiegelhalter, a University of Cambridge statistician, said something along those lines in relation to drinking risks). The fact that the risk of deaths related to gunshots, drug overdoses, and suicides are higher than different types of auto accidents suggests that these fatalities—which are often presented as tragic, isolated events—are actually far more normal than they should be. In fact, these deaths actually contributed to the US’ falling life expectancy.

Meanwhile, your lifetime odds of dying in a rare tragedy—like from bee stings, dog bites, or train or plane crashes—are still pretty low. You can view the full lifetime odds here.

Bonus fact: Over time, the odds of death from falls have gone up. Falling hasn’t become more common or dangerous, though. Instead, a larger portion of the US population is above 65, and these are the people most likely to die from falling.

The fact that the brain feels no pain is both a blessing and a curse.

Found while reporting: Scientists identified a protein in the blood that could predict Alzheimer’s.

I find it particularly ironic that the brain, the organ responsible for interpreting all the sensations of feeling all over our bodies, cannot feel physical pain itself. This is because the brain has no nociceptors, which are responsible for detecting unpleasant sensations (worst job ever!).

As this piece in The Conversation points out, our heads do have other structures that can feel pain, like blood vessels and muscles (which is why we feel headaches and maybe migraines, but they’re still poorly understood).

Although physical discomfort is something we try desperately to prevent, it’s not always good to be totally blinded from it. Pain is what alerts us that something is wrong and needs attention and care.

One of the main challenges of Alzheimer’s is that it can painlessly degrade the brain for decades. When a person starting having cognition problems—not being able to make quick decisions, trouble planning, or difficulty remembering things—it feels like a sudden surprise.

Although feeling no neuron pain in some ways is a blessing, it’s been a huge challenge for researchers studying Alzheimer’s disease. Because it’s asymptomatic for so long, by the time a person shows up with symptoms, her brain is seriously, irreversibly damaged. Drug trials, therefore, often end up recruiting participants they likely couldn’t save anyway, because the disease has progressed too far. (I wrote about this a lot more in this piece from May 2018.)

This week, I reported interesting results from early work showing that it may be possible to detect Alzheimer’s with a simple blood test, years earlier before people start to show symptoms. If this work can be validated, it could be that we’d all get routine screenings at a certain age to see if we’d be eligible for clinical trials, or eventually, to receive treatment before the disease progresses.

Bonus long read: In 2017, Emily Hayasaki wrote a fascinating piece for Wired about a gene that may be responsible for how we feel pain. She managed to find individuals who have over and under-active sensations of pain. Check it out here.

Some bacteria employ protein henchmen that can also wreak havoc in our bodies.

Found while reporting: A common oral infection may contribute to Alzheimer’s disease.

Sometimes, it’s not the bacteria themselves that harm our bodies—it’s what they spew out.

Take Porphyromonas gingivalis, a type of bacteria that can cause gum disease. Some estimates suggest that about half of all US adults over 30 have it, but only about one in 10 have severe cases. It’s not great—it can lead to tooth decay.

Researchers this week published work on mouse and cell models that showed that when P. gingivalis reaches the brain, it can cause the same damage we see in people with Alzheimer’s. (How do bacteria get to the brain, you may ask? Probably by hitching a ride on white blood cells or creeping up the cranial nerve.)

But P. gingivalis isn’t doing the dirty work. Instead, it shoots out these short little protein chains called gingipains (because they’re a real pain amirite?). These gingipains basically go around and slice and dice proteins we need and get the immune system all riled up in ways that can also damage nearby cells.

Sure enough, the same team found evidence of both genes from P. gingivalis and gingipains in the saliva and spinal fluid of people with Alzheimer’s, and the brains of those who had passed away with the disease.

The bad news is P. gingivalis tend to carry genes (paywall) that make them resistant to antibiotics. But the good news is, scientists were able to create another compound that neutralized the gingipains and reversed some of the damage they did in mouse brains. It could be a possible therapy for Alzheimer’s in the future.

Side note: A few news outlets reported headlines stating that P. gingivalis was the cause of Alzheimer’s, and I thought this was irresponsible for a few reasons. You can read about them in this Twitter thread.

Stuff I learned from others:

Liver transplants for people with alcohol-related liver damage have gone up, but that’s a good thing! The policy that stated liver transplant recipients had to be six months sober was based on bad science, and it was finally reversed. From Chase Purdy for Quartz.

Hermit crabs have evolved to have giant genitals so they can mate without leaving their shells, from Jake Buehler for National Geographic.

The word “influenza” comes from the Italian word influenzare, which means “to influence.” The reason the flu got its name is because before germ theory, ailments were considered to be the result of the stars’ influence, from Johanna Mayer for Science Friday’s “Science Diction” newsletter. Sign up here!

Animal of the week: Whale sharks.

Last week, I reported a story about a study that showed that whale sharks may actually be more omnivorous, like bears (and us!). We don’t know a lot about the world’s biggest shark (and fish in the sea!) because they’re kind of hard to study. They spend a lot of time in the warm open ocean, which makes them hard to reach, and illegal fishing has diminished their population.

But we do know that this school bus-sized fish filter feeds (just like some giant whales) except they use their gills to push water away from tasty treats like krill, squid, fish, prawns, and possibly algae and seagrass!

SO BIG.

Long read of the week: My former colleague Karen Hao looked at thousands of abstracts of papers about AI to figure out where the field’s been, and where it’s going. Her final piece is full of clear writing and gorgeous graphics, and you can read it here.

That’s all for now. Stay curious, friend! <3

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