NEW YORK (VINnews) – Scientists have long known that blood type matters when it comes to transfusions. But a sweeping new study suggests your blood type — whether A, B, O, or AB — may quietly influence the risk for a surprising range of diseases, from cancer to COVID-19 to heart problems.

But before anyone rushes to add their blood type to a shidduch resume — don’t. The numbers above, while genuinely interesting to researchers and physicians, represent statistical trends across large populations, not individual destiny. A Type B person may never develop diabetes. A Type O person is not immune to cancer or COVID-19.

Blood type is a far cry from a prediction. It is a statistical association — meaningful in a laboratory or a doctor’s office, but not the kind of information the Rama had in mind, and not something that belongs on a resume alongside height, profession, and which yeshiva someone attended. The shadchanim of the world can rest easy.

But here are the findings. Researchers in one of the most comprehensive reviews ever conducted on this topic, publishing their findings in BMC Medicine, a respected peer-reviewed journal, analyzed 51 separate scientific studies covering 270 different health questions, all asking the same basic thing: does blood type make one more or less likely to get sick?

Their answer: quite possibly — and in some cases, the evidence is strong enough to take seriously.

The Biggest Finding: Blood Type B and Diabetes

The clearest result from the research involved Type 2 diabetes, the form of diabetes closely linked to lifestyle and diet that affects tens of millions of Americans. People with Type B blood were 28% more likely to develop Type 2 diabetes compared to people with any other blood type. The researchers described this finding as “convincing” — their highest level of confidence — meaning the data held up across multiple checks for reliability and bias.

Why might this be? Scientists believe blood type may influence the trillions of bacteria living in the gut, which in turn affects how the body processes sugar and manages inflammation. Blood type also appears to be connected to certain proteins in the body that are known to raise diabetes risk.

Heart Disease and Blood Clots

The research also turned up strong evidence connecting blood type to cardiovascular disease. People with Type A blood, as well as anyone who is not Type O, showed a significantly elevated risk for venous thromboembolism — dangerous blood clots that can form in the legs or lungs. Specifically, Type A individuals were 63% more likely to develop such clots compared to Type O individuals, while non-O blood types overall were a staggering 110% more likely — meaning more than double the risk.

The likely explanation involves a protein called von Willebrand factor, which helps blood clot. People with Type A or Type B blood tend to have higher levels of this protein circulating in their bloodstream, making clots more likely.

Type A blood was also linked to higher rates of myocardial infarction — heart attacks — with Type A individuals facing a 29% greater risk compared to Type O.

Now, a major study adds a troubling new dimension to this cardiovascular picture — one specifically involving COVID-19. Researchers from Cleveland Clinic and the University of Southern California, publishing in late 2024 in the journal Arteriosclerosis, Thrombosis, and Vascular Biology, analyzed data from nearly 228,000 individuals in the UK Biobank. They found that hospitalization for COVID-19 more than doubled the risk of heart attack or stroke among patients with A, B, or AB blood types — but not among those with Type O, which appeared to offer some protection. The risk of heart attack and stroke was roughly 65% higher in adults with non-O blood types compared to those with Type O blood.

The heightened risk persisted for nearly three years after the initial infection — a finding the researchers described as having significant implications for global cardiovascular health, given that over a billion people worldwide have had COVID-19. The authors suggested that physicians should consider a history of COVID-19 — especially severe COVID-19 requiring hospitalization — as a factor in cardiovascular risk assessment, in the same category as established risk conditions like diabetes. The increased risk of adverse cardiac events in severe COVID patients was comparable to the risk seen in patients who already have coronary artery disease or other major cardiovascular risk factors.

Cancer Connections

Across dozens of cancer studies, researchers found several patterns worth noting. People with Type A blood faced a 19% higher risk of stomach cancer compared to Type O, and a striking 33% higher risk of pancreatic cancer. Type B blood was linked to a 20% higher risk of pancreatic cancer and a 20% higher risk of esophageal cancer. Type O blood, often considered the “universal donor” type, appeared to offer some protection against several cancers.

These findings were rated as “highly suggestive” or “suggestive” — not quite as rock-solid as the diabetes finding, but consistent enough across multiple studies to warrant attention.

A New Frontier: Blood Type and Children

Until now, virtually all of the research on blood type and disease has focused on adults. A landmark study published in January 2026 in the journal Translational Pediatrics is the first ever to investigate the relationship between ABO blood groups and disease categories specifically in the pediatric population. Analyzing data from over 36,000 children treated at a major Chinese children’s hospital, the researchers found distinct associations between blood groups and disease distribution across different body systems: blood group A correlated with ear, nose, and throat conditions; group B with neonatal medicine diseases; group AB with neurological diseases; and group O showed an inverse relationship with both ENT and neonatal conditions.

The authors were careful to note that these patterns in children differ meaningfully from the adult data, and that multi-center validation is still needed before clinical conclusions can be drawn. But the study opens a genuinely new chapter. A second 2026 study, published in the European Journal of Haematology and examining blood type distribution among 540 children with leukemia, found no statistically significant association between blood type and leukemia subtype in children — a reassuring null result suggesting that the blood-type/cancer connections documented in adults do not straightforwardly extend to childhood malignancies.

Cognitive Decline: A New Concern for Type AB

More recent research has highlighted a risk not prominently featured in earlier reviews: cognitive decline. Type AB individuals appear to develop memory problems and cognitive decline at higher rates than other blood types, particularly as they age, with higher rates of dementia and memory impairment compared to other groups. The reasons remain under investigation, but one leading hypothesis involves Factor VIII — a clotting protein that tends to be elevated in Type AB individuals and has been associated with cognitive decline in large population-based studies. Type AB is the rarest of the four blood types, but for those who carry it, this finding is worth discussing with a physician, especially as screening tools for early cognitive changes continue to improve.

Infectious Diseases

The research found noteworthy patterns with infections as well. Compared to Type O, people with Type A blood were 25% more likely to contract COVID-19, while Type B individuals were 15% more likely. Type O blood also appeared to offer some protection against malaria caused by the parasite Plasmodium falciparum — non-O blood types were 86% more likely to become infected — a finding consistent with decades of earlier research from tropical regions.

The researchers were careful to note that strong statistical patterns don’t always tell the whole story. Most of the underlying studies they reviewed were observational — meaning scientists tracked people over time rather than running controlled experiments. That makes it harder to prove that blood type directly causes these diseases, as opposed to being connected to them through some other factor.

Blood type is just one of many factors that influence health, alongside diet, exercise, genetics, and environment. Knowing your blood type won’t replace regular checkups or a healthy lifestyle.

Still, the study’s authors believe this kind of research can help doctors identify people who may be at higher risk for certain conditions — and intervene earlier.

If you don’t know your blood type, your doctor can determine it with a simple blood test. If you’re Type B, the research suggests it may be worth paying extra attention to your blood sugar levels and discussing diabetes screening with your physician. If you’re Type A or non-O, staying alert to the signs of blood clots is worth a conversation with your doctor — and if you’ve had a significant COVID-19 illness, the newer evidence suggests your cardiologist should know that too. If you’re Type AB, the emerging connection to cognitive decline is a reminder that brain health screenings deserve attention as you age. And if you’re a parent, the newest pediatric research — still early, but intriguing — suggests that blood type may eventually become a useful tool in children’s medicine as well.

Researchers are still working out exactly why blood type influences disease. But the message from this growing body of research is clear: the letters on your blood type label may mean more than most people ever realized — just not enough to change how we find a shidduch.