Issue 72

The myriad causes of dementia, stressed out eyeballs, and our shrinking brains

May 18, 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.

Archives from Tinyletter can be found here.

Usually, dementia is the result of rogue clumps of misshaped proteins in the brain. The trouble is finding which one is causing it.

Found while reporting: The identification of another form of dementia shows just how complicated the condition can be.

We talk about dementia a lot, and it’s important to remember that it’s not a specific condition. It’s a term like insomnia. Not being able to fall or stay asleep has a number of different causes.

Dementia technically refers to two or more cognitive functions deteriorating to the point where they impede with a person’s day-to-day activities. Alzheimer’s is the most common form of dementia, and has a specific pathology—buildups of plaques called amyloid and tau tangles (which kind of look like little tornadoes) in specific regions in the brain.

But there are so many other causes of dementia. I made this handy table to break it all down.

In most cases people have multiple kinds of pathologies—which is probably why each of these conditions individually have so few treatments. It’s a good reminder of Hickam's dictum: patients can have as many conditions as they damn well please.

Your eyes’ stress reactions can damage themselves.

Found while reporting: The blue light from your LED screen isn’t hurting your eyes.

Every now and then, my job requires me to debunk junk headlines on the internet.

Earlier this week, a bunch of headlines cited a report from a French government agency that said the blue light wavelengths from LED lights were dangerous to eye health. That’s not the whole truth, as you may imagine.

LED lights are those present in the screen you’re reading this on, and they (and the blue light they emit) are not strong enough to damage your retinas with their brightness. (Shout out to Dr. Ola Pietraszkiewicz, a newly minted ophthalmologist, for calling BS on some poorly written headlines!) While there are lights strong enough to do this, they’re required to have warning labels, and are only present in industrial settings.

Still, that doesn’t mean you should ever look directly into any light source (including the sun!). The danger is that bright lights tend to send our eye’s light-sensing cells (called photoreceptors) into a tizzy. These cells, which are located in the part of the eye called the retina, send out little bursts of chemicals when they detect light, as if to say, “Hi! Hello! There is a bright spot ahead!

When they fire all at once, they take a second to recover. This is why you may need to blink after starting into a headlight of a car on the opposite side of the road at night.

If you keep staring at a bright light, though, your photoreceptors will release so many stress chemicals (essentially screaming, “Stop! Please! Look away! It’s so easy, that’s what the lids are for!”) they damage the surrounding areas of the eyeball. This damage can take up to a year to heal.

Our brains start shrinking in our 20s.

Found while reporting: Scientifically, this is the best age for you to lead.

Friend, this fact may seem like a sad fact. But in reality, it’s a remarkable fact.

Even though brains lose some of their size as we get older, they’re not losing brain cells. Instead, neurons are getting smaller, and they’re shifting the connections they have with other brain cells.

Some of these changes result in normal, cognitive slow down. As we age, we may have more trouble remembering new names and faces, recalling words, or remembering why we walked into a room (all three happened to me this week at least once).

But the brain is a resilient organ and adapts over time. It starts using new tricks, like incorporating other areas of the brain to complete tasks, so it can function nearly as well as a younger brain.

These neurological changes also seem to help us develop new skills, like handling negative emotions, or valuing the present just as much as we value the future. (Younger adults tend to think of the present as The Most Important Time to worry about, which can make saving for retirement hard.) Both of these are qualities we tend to think of maturity, and these neurological changes help.

Crucially, all brains are different. The way they are in our 20s and their rate of change over time is incredibly variable among people. Just like no two people are the same in the present, no two people will age exactly the same way, either.

Stuff I learned from others:

Sunscreen doesn’t reduce melanoma in black people, from Adewole S. Adamson, a dermatologist, writing for The Conversation.

Roughly third of the world’s dwindling helium supply is used for cryogenics, from Whet Moser in an obsession email for Quartz.

Animal of the week: Beluga whales

While on vacation, we stopped at the Georgia Aquarium. I love aquariums, and this place had five (5!) beluga whales.

My favorite beluga facts are that they don’t have dorsal fins (the one on their backs) because they’d hit it on ice too often. They’ve got a more mobile neck to help them catch prey up on ice. They can also swim in freshwater to raise their calves. And even though they have teeth, they tend to swallow their food whole. Much like yours truly!

Image description: Two beluga whales swimming in circles around each other.

Photo credit: Benjamin Daniels

Long read of the week: If you liked my series on direct-to-consumer genetic tests, I think you’ll like this incredible deep dive into the world of stem cell therapies. Check out this piece by Caroline Chen for ProPublica for more.

Image description: a sketched headshot of me.

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

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