Forty-three percent of Americans don’t know their blood type according to a 2019 survey by Quest Diagnostics — fewer than how many have memorized their Wi-Fi password. But recent links between blood type and COVID-19, or even susceptibility for other diseases, mean you might want to know your type.
A recent study by Harvard Medical School researchers based at Massachusetts General Hospital found blood type is not related to the severity of symptoms of COVID-19. However, the study also found symptomatic people with some blood types may have a higher chance of testing positive for COVID-19.
So few people know their type, not because that information isn’t available, but likely because no health care provider has ever told them, said Chancey Christenson, associate director of the University of Chicago Blood Center and medical director of clinical pathology informatics. Christenson, also an associate professor in transfusion medicine, said if you’ve had your blood drawn, your blood type is probably already on file.
Blood type is determined by the carbohydrate chains — also known as antigens — that hang off your red blood cells, Christenson said. There are A and B antigens. Type A blood has the A antigen and Type B blood has the B antigen. AB blood has both antigens and Type O blood has neither.
Knowing whether you are Type A, B, AB or O is most important in the event you need a blood transfusion. “If you ever need blood, it’s simpler if you already know your type,” he said.
But knowing your type may also help you understand more about your health, Christenson said.
Type O blood is known as the universal donor — meaning any blood type can accept O blood — because it has no antigens, Christenson said. Having no antigens on the red blood cells also makes people with Type O blood less prone to bacterial infections, he said.
Christenson said people with Type O blood are also at a lower risk for heart and vascular diseases, but are more likely to get norovirus.
“The type of your blood is showing you what is happening in the rest of your body,” Christenson said. “The ABO antigens are everywhere.” He said they can be found in blood vessels and gut lining.
Type A blood has a higher clotting factor, Christenson said, which makes for an increased risk of heart disease, heart attack and DVT. He said people with Type A blood may have more pronounced hangovers.
People with type AB are more predisposed to these clotting problems, Christenson said.
If you have Type B blood, you may have an increased risk for pancreatic cancer and a lower risk of meningitis, he said. Group B people may also experience better digestion.
“You can’t change your blood type,” Christenson said. “So, it’s a risk factor just like any other risk factor.”
Anahita Dua, senior author of the Harvard Medical School study, said researchers did find a correlation between blood type and likeliness to test positive for COVID-19 when symptomatic. The observational data collected showed patients with AB or B blood types who were Rh+ had higher odds of testing positive when they came in with symptoms such as coughing or lack of taste and smell, Dua said. Symptomatic patients with Type O blood were less likely to test positive for COVID-19.
However, she said blood type is not the risk factor people should be concerned about when it comes to COVID-19.
“(This study) helped us start to put to rest ... the notion that blood type was in fact a very important predictor of how patients either got COVID-19 or how they did once they had COVID,” said Dua, who is also the director of the Massachusetts General Hospital Vascular Lab.
Regardless of blood type, Dua said people need to adhere to the safety precautions that are known to be effective in preventing the spread of COVID-19 — wearing a mask, socially distancing and washing your hands.
“You can’t control what blood type you are, but you certainly can control whether you wear a mask,” she said.
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