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15 Questions About Donating Blood, Answered

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You’ve rolled up your sleeve, faced a fear of needles, and risked passing out mid-donation. Congrats, you’re one of the roughly 6.8 million people who donate blood each year! But even if you’ve shimmied onto that cot and happily accepted your post-blood draw cookie, you still may have questions about the process. We've answered some of the big ones.

1. WHERE DOES THE DONATED BLOOD GO?

When you needle up for the American Red Cross, they collect roughly one pint of blood and several test tubes—all of which are stored in iced coolers until they can be transported to an official Red Cross center. From there, the samples are spun in centrifuges to separate the red cells, platelets, and plasma and the tubes are sent out for testing at one of three national labs.

Samples that come back disease-free are then stored at the center—red cells last in a 6 ºC refrigerator for up to 42 days; platelets remain at room temperature in agitators up to five days (and are frozen for up to a year)—until they are shipped to a hospital for use.

2. WHAT DO THEY TEST FOR?

Your vials undergo a dozen tests designed to both establish blood type and to weed out donations laced with infectious diseases, such as HIV, hepatitis B and C, and syphilis. If your sample tests positive for something, your donation will be trashed, but on the upside they’ll reach out and let you know about your diagnosis and offer up counseling with a trained professional.

3. WHAT EXACTLY ARE PLATELETS, ANYWAY?

The tiny, disc-shaped particles inside your blood help it to clot. They’re needed for patients with diseases (such as aplastic anemia and leukemia) that hamper the body’s ability to clot and patients who are undergoing major surgeries. Platelets are separated from your red blood cells after you donate and can only be stored up to five days. Thus, maintaining a large enough supply can be an issue.

4. HOW MUCH BLOOD IS NEEDED TO SAVE A LIFE?

It depends on the situation. According to the American Red Cross, the average red blood cell transfusion is roughly 3 pints, but a single car accident victim could need up to 100 pints.

5. ARE CERTAIN BLOOD TYPES MORE VALUABLE THAN OTHERS?

Yes. O positive is the most common blood type in America—belonging to about 39 percent of the population—and thus, the most likely to be needed for a transfusion. (Type A positive ranks second at 31 percent of the population.) O negative blood types—that’s about 9 percent of people—are considered the universal donor because their blood can be given to anyone. The least common blood type? AB negative—belonging to just 1 percent of people.

6. HOW MANY PEOPLE DONATE EACH YEAR?

Not enough. The American Red Cross estimates that 38 percent of the United States population is eligible to donate blood at any given moment—but less than 10 percent of those people do. Each year, roughly 6.8 million donors give 13.6 million units of blood. That may sound like a lot, but approximately 36,000 units are needed across the U.S. each day and because of the short shelf-life, it’s difficult to build up an inventory of blood if a lot is needed quickly.

7. WHO ISN'T ELIGIBLE TO DONATE?

Some states allow 16-year-olds to donate with parental consent, but most require blood givers to be at least 17. You also have to weigh a minimum of 110 pounds and be in good general health. (If you have a cold, flu or fever, you will be turned away.) Being a world traveler could also be an issue. Those who have recently visited countries where diseases such as malaria or the Zika virus are common are required to wait a set amount of time before offering up a vein. Piercings and tattoos can also temporarily prevent you from donating depending on how long ago you acquired them.

8. IS THERE ANY WAY TO SPEED UP THE PROCESS?

While the Red Cross estimates donating blood can take more than an hour—from the time you fill out your paperwork until you accept the post-donation cookie—you can cut out some time with RapidPass. Users complete forms online, then print them off and bring them to the donation site. For a true walk-in, walk-out experience you can also schedule an appointment. Once you’re all set up, the actual blood draw only takes about 10 minutes.

9. HOW DOES MY BODY REPLACE THE BLOOD LOST?

The average adult has between 10 and 12 pints of blood in their body. Since your bone marrow churns out a constant supply of red cells, plasma, and platelets, the plasma you give is replaced within the first 24 hours.

10. WAIT, THEN WHY DO I HAVE TO WAIT 56 DAYS BETWEEN DONATIONS?

While the plasma is replenished quickly, it can take four to six weeks for your body to manufacture the red blood cells that are lost. If you’re only donating platelets, which your body replaces within a day, you can give again after a week. However, you’re restricted to only 24 total platelet donations a year.

11. DO I NEED TO DO ANYTHING SPECIAL AFTER DONATING?

The American Red Cross suggests replacing the lost iron with foods such as spinach, beans, and red meat as well as drinking an extra 4 to 8 ounces of non-alcoholic liquid. They also advise against doing heavy lifting and recommend keeping your bandage on for at least five hours. (Bonus: that makes it easier to brag to your friends about your largesse!)

12. WHY DO THEY ASK FOR MY ETHNICITY?

According to the New York Blood Center, knowing your race makes it easier to match your blood with a needy recipient. “Blood types and antigens are inherited, just like eye and hair color,” reads an entry on their website. “Searching for very precise transfusion matches can be like looking for a needle in a haystack, so it makes sense to begin with donors of the same ethnic or racial background as the transfusion recipient.”

13. CAN YOU REALLY MAKE MONEY DONATING BLOOD?

You can score between $25 and $50 for donating plasma at one of the 530 licensed and IQPP certified plasma collection centers in the U.S., Canada, and Europe. The process is similar to donating blood, except that once the whole blood is drawn, the plasma is separated out and the rest of the blood is returned to your body. (The whole procedure takes between 90 minutes and two hours.) However, this plasma usually doesn’t go straight to disease-stricken donees. Instead, it’s given to pharmaceutical companies who use it to create medicine for a range of conditions.

14. CAN I DONATE BLOOD TO MYSELF?

Yes, but it takes some legwork. You can do what’s called an autologous donation—where you donate blood to be used on yourself during a surgery or planned medical procedure—but you’ll need a prescription from your doctor.

15. IS THERE ANY SUBSTITUTE FOR BLOOD?

Not yet. However the American Red Cross says they are diligent about tracking research that might help identify an alternative. “The Red Cross actively follows blood substitute research,” reads a note on their site, “and works closely with other organizations that develop new transfusion alternatives.”

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Health
The First Shot to Stop Chronic Migraines Just Secured FDA Approval
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Migraine sufferers unhappy with current treatments will soon have a new option to consider. Aimovig, a monthly shot, just received approval from the Food and Drug Administration and is now eligible for sale, CBS News reports. The shot is the first FDA-approved drug of its kind designed to stop migraines before they start and prevent them over the long term.

As Mental Floss reported back in February before the drug was cleared, the new therapy is designed to tackle a key component of migraine pain. Past studies have shown that levels of a protein called calcitonin gene–related peptide (CGRP) spike in chronic sufferers when they're experiencing the splitting headaches. In clinical trials, patients injected with the CGRP-blocking medicine in Aimovig saw their monthly migraine episodes cut in half (from eight a month to just four). Some subjects reported no migraines at all in the month after receiving the shot.

Researchers have only recently begun to untangle the mysteries of chronic migraine treatment. Until this point, some of the best options patients had were medications that weren't even developed to treat the condition, like antidepressants, epilepsy drugs, and Botox. In addition to yielding spotty results, many of these treatments also come with severe side effects. The most serious side effects observed in the Aimovig studies were colds and respiratory infections.

Monthly Aimovig shots will cost $6900 a year without insurance. Now that the drug has been approved, a flood of competitors will likely follow: This year alone, three similar shots are expected to receive FDA clearance.

[h/t CBS News]

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Medicine
The 98.6℉ Myth: Why Everything You Think You Know About Body Temperature Is a Lie
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When you were kid, you probably knew that to score a magical sick day home from school, you needed to have a fever. When the thermometer came out of your mouth, it had to read higher than 98.6℉—the long-accepted "normal" human body temperature. (If you wanted to really seal the deal, you may have hoped to hit 100℉.) Since then, you may have used a temperature above 98.6℉ as a metric to work from home (or call out sick entirely).

But here's the thing: The average body temperature isn't actually 98.6℉—a fact that we've known for more than 25 years. The myth originated in the 19th century with a single doctor, and despite evidence to the contrary, it's persisted ever since.

THE GIANT—AND FAULTY—ARMPIT THERMOMETER

In 1851, Carl Wunderlich, the director of the hospital at Leipzig University, began going from room to room with a comically large thermometer in tow. He wanted to understand how body temperature is affected by different diseases, so in each room, he would hold the foot-long device in patients' armpits for a full 20 minutes, waiting for a temperature to register. Once it did, he'd note the temperature on the patient's chart (Wunderlich is thought to be the first physician to do so). He and his staff did this for years, repeatedly taking the temperatures of some 25,000 patients and logging them on their charts, until he had millions of readings. In 1868, he finally published this data in Das Verhalten der Eigenwarme in Krankheiten (On the Temperature in Diseases: A Manual of Medical Thermometry). He concluded that the average human body temperature was 98.6℉, underscoring the idea that fever is a symptom of illness, not a cause.

No one questioned Wunderlich's methods, or his average, for about 140 years. Then, in the early 1990s, internist Philip Mackowiak—a professor of medicine at the University of Maryland, a medical historian, and, apparently, a clinical thermometer junkie—saw one of the physician's instruments at the Mutter Museum in Philadelphia. He told the Freakonomics podcast that he'd always had doubts about the 98.6℉ standard. "I am by nature a skeptic," he said. "And it occurred to me very early in my career that this idea that 98.6 was normal, and then if you didn't have a temperature of 98.6, you were somehow abnormal, just didn't sit right."

Getting his hands on Wunderlich's thermometer—which the museum let him borrow—only deepened his doubts. The huge thermometer was unwieldy and non-registering, meaning, Mackowiak explained, "that it has to be read while it's in place." Not only that, but Wunderlich had used the device to measure temperatures in the armpit, which is less reliable than temperatures taken in the mouth or rectum. The instrument itself also wasn't terribly precise: It measured up to 2 degrees Centigrade higher than both ancient and modern instruments.

In 1992, Mackowiak decided to test Wunderlich's average. Using normal-sized oral thermometers and a group of volunteers, he determined that the average human body temperature actually hovers around 98.2℉. Mackowiak found that body temperature tends to vary over the course of the day, with its lowest point around 6 a.m. and its highest in the early evening. Body temperature can also fluctuate monthly (with the menstrual cycle) and over a lifetime (declining decade by decade with age), and may even be differentially linked to sex and race assignments. He concluded that normal body temperature is so unique to each person that it's almost like a fingerprint and, given that wide variation, not actually a very reliable indicator of illness.

As a result of his study, Mackowiak proposed raising the threshold for fever to 98.9℉ for temperatures taken in the morning (and 99.9℉ at other times). While it's a relatively minor change in terms of actual degrees, this fever threshold is actually lower than the CDC's, which is a temperature of 100.4℉ or higher.

There are potential real-life consequences in this gap, for everyone from students (who'd have to attend school with what would be considered a low-grade fever by Wunderlich's 98.6℉ standard) to employers and daycares (who use temperature to set attendance policies). What's more, anyone who is actually sick but ignores a low-grade fever—one that meets Mackowiak's threshold but still falls under the CDC's—could pose a risk to people with compromised immune systems trying to avoid unnecessary exposure to illness in public places.

THE BALANCING POINT

There's a reason the average trends near 98℉ instead of 92℉ or 106℉. As endotherms, mammals expend a great deal of energy maintaining body temperature when compared with cold-blooded creatures. To find and conserve a just-right body temperature, central nervous system sensors gather data (too warm? too cold? just right, Goldilocks?) and send that information to the pebble-sized hypothalamus near the base of the brain. There, the data is converted into action: releasing sweat and widening the blood vessels if too warm; raising metabolism, constricting the blood vessels, and inducing shivering if too cold.

According to a study by Aviv Bergman and Arturo Casadevall in the journal mBio, the precise balancing point for ideal body temperature is the sweet spot where the metabolic cost for all this thermoregulation balances with the evolutionary advantage of warding off fungal disease. (While warm-blooded animals are prone to bacterial or viral infections, they rarely experience fungal infections because most fungi can't withstand temperatures above 86℉. Cold-blooded animals, on the other hand, are prone to all three.) For Bergman and Casadevall, this benefit even explains what tipped Darwin's scales in favor of mammals, allowing them to edge out other vertebrates for dominance after the Cretaceous-Tertiary mass extinction wiped out the dinosaurs.

Of course, rules call for exceptions, and the one place where human body temperature demonstrates sustained elevation is outer space. Astronauts on prolonged missions clock significantly higher average body temperatures than they do when terrestrial—even up to 104℉. This so-called "space fever" is probably a product of some combination of radiation exposure, psychological stress, and immune response to weightlessness. Researchers believe this phenomenon could yield crucial information about thermoregulation—and may even offer insight into how humans might adapt to climate change.

WHY THE MYTH PERSISTS

It's been 26 years since Mackowiak's study, yet the newer data has not taken hold among medical professionals or the public. What gives?

Mackowiak tells Mental Floss that he finds it a bit mystifying that the myth persists, especially since many people, when pressed, know that the so-called "average" temperature varies. Part of the problem may be psychological: We cling to beliefs despite evidence to the contrary—a phenomenon called belief perseverance [PDF]. It's a significant force upholding a surprising number of medical myths. The idea humans should drink eight glasses of water a day? Not science. Sugar causes hyperactive behavior? Nope. Reading in dim light harms eyesight? Not really.

Unlearning persistent myths—especially ones loaded with the weight of medical authority—is difficult. "Deep down, under it all," Mackowiak says, "people want simple answers for things."

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