LOS ANGELES — Potentially good news for the 45 percent of Americans who have Type O blood: Researchers said Tuesday that those people appear to have a slightly lower risk of developing heart disease than their neighbors with Type A, B or AB blood.
Dr. Lu Qi, an assistant professor of nutrition at the Harvard School of Public Health in Boston, analyzed heart disease risk in two large, multi-decade health studies — reviewing data collected from 62,073 women who participated in the Nurses’ Health Study, which was launched in 1976, and from 27,428 men who took part in the Health Professionals Follow-up Study, launched in 1986.
Adjusting for heart disease risk factors including diet, diabetes status, gender and race, Qi and his colleagues found that study participants with type AB blood had the largest heart disease risk — 20 percent greater than that of people with Type O blood. (The team calculated that the incidence of heart disease was 125 cases per 100,000 person-years.) Type B was next with an 11 percent greater risk, and type A was third with an 8 percent greater risk, the scientists reported.
The trend held up when the researchers compared their results with several other population studies recording the same factors. Across a total of seven studies, the increased risk for people with non-O blood types was 11 percent higher than that for people with Type O.
Rh factor — the “positive” or “negative” often included in blood typing — was not correlated with any differences in heart disease risk.
The analysis was not designed to identify the reasons why blood type might influence heart disease risk. But the researchers noted that non-O individuals have higher levels of two proteins involved in clotting and atherosclerosis — and that people with Type A blood, in particular, have been reported to have higher levels of serum total cholesterol and LDL (bad) cholesterol.
Harvard’s Qi said that learning more about the relationship between blood type and heart disease risk could help doctors tailor their advice — perhaps urging patients with Type A blood to watch their cholesterol more carefully, for example.
“Our findings might help physicians better understand who is at risk for developing heart disease,” he said.