Here Are 8 Important Reasons Why You Should Know Your Blood Type

Many Americans don’t know their blood type, but that knowledge can actually tip you off about your risk for certain medical conditions.

What’s in a blood type?

Potentially a lot, according to several studies that correlate different blood groups with everything from risk of heart disease to infertility. While none of these studies are conclusive about cause and effect (they can’t say X blood type causes Y disease) and any increased risks are still pretty small, the research does highlight the importance of knowing your type—A, B, AB, or O—and how it could affect your well-being.

1. Blood clots: Type AB, A, and B increases risk

Danish researchers have studied how blood type interacts with a genetic predisposition for deep-vein thrombosis (DVT), or blood clots in the lower legs that can travel to the lungs and become life-threatening. After analyzing data on about 66,000 people over more than 30 years, they found that those with type AB, A, or B had a 40 percent higher risk of DVT than people with type O, the most common type.

When the scientists did further analysis to see which factors have the biggest impact on DVT risk on a population level, they found that an AB blood type contributed to about 20 percent of blood clots; genetic mutations accounted for 11 percent, being overweight accounted for 16 percent, and smoking accounted for 6 percent, reported

2. Heart disease: Type AB, B, and A all increase risk

When Harvard scientists analyzed more than two decades of data on more than 77,000 people, they found that those with AB blood had a 23 percent increased risk for heart disease compared to people with type O blood. Those with type B blood had an 11 percent higher risk and those with type A blood had 5 percent greater risk. Researchers aren’t sure why, but posit that type A blood is associated with LDL cholesterol and that type O blood, which is associated with reduced risk, may contain a chemical that boosts blood flow and prevents clots.

However, researchers are quick to point out that lifestyle factors like weight, smoking, and diet, which, unlike blood type, are modifiable, have a much greater impact on heart disease.

3. Stomach cancer: Type A increases risk

People with blood group A had a 20 percent greater chance of developing gastric cancer compared to people with blood group O, according to a Swedish study from the Karolinska Institute. These people may be more vulnerable to other stomach cancer risk factors such as cigarette and alcohol use, according to

Meanwhile, the same Swedish paper found that those with type O blood had an increased risk for stomach ulcers; they may be more susceptible to the Helicobacter pylori bacteria that cause the stomach sores.

4. Fertility: Type O reduces it

Women with this blood type were twice as likely to have blood levels of the hormone FSH high enough to indicate low ovarian reserve, a measure of fertility, according to an Albert Einstein College of Medicine study. Researchers couldn’t say for sure why, though. Given that type O blood is the most prevalent across all U.S. ethnicities, it doesn’t pay to worry too much about it. Age is a far more important risk factor for fertility problems.

5. Pregnancy risks

This has nothing to do with your “letter” blood type, or the type determined by the ABO grouping system. This has to do with the Rh factor, which determines whether your blood type is positive or negative. This factor could cause complications in pregnant women if the baby’s Rh blood type is different from the mother’s. For instance, if the mother has a negative blood type and the baby has a positive one, the mother’s body can actually build up antibodies against the baby’s blood type. Luckily, this doesn’t affect the baby, but it could have a disastrous effect on future pregnancies. Fortunately, doctors can give pregnant women a shot early in their pregnancy that can prevent Rh-incompatibility problems.

6. Dementia and memory loss: Type AB increases risk

Neurology study revealed that people with type AB blood have a much higher chance of suffering from memory loss later in life. Individuals with AB type have a whopping 82 percent higher chance, most likely because they have larger amounts of the factor VIII protein, which helps with blood clotting. Participants in the study who had higher levels of this protein were 24 percent more likely to develop memory problems, regardless of their blood type. As in most of these cases, though, blood type is far from the only, or even most important, factor that affects your risk. High blood pressure, diabetes, smoking, and other habits all increase your risk of dementia.

7. Stroke: Type O has the lowest risk has found that people with a blood type other than O (the most common) have a 9 percent higher risk of cardiovascular issues such as stroke. Biologists are still investigating why this might be; one possible explanation is that non-O blood types contain more of the Von Willebrand factor, a protein that has been connected to blood clotting and stroke in the past.

8. Mosquitoes like Type O blood

If you find yourself scratching bug bites all summer long, your blood type might be to blame. Type Os are as much as twice as attractive to mosquitoes as type As, with type Bs falling in the middle. In addition, 85% of people secrete a substance that”broadcasts” their blood type to mosquitoes. Those little blood-suckers are far more attracted to those people, no matter what their blood type is.


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