ORLANDO, Nov. 11 -- Further deepening a decade-old medical controversy, Finnish researchers have linked the amount of iron in the body in men to heart attacks. The new study, which uses more precise techniques than earlier research, was reported today at the American Heart Association's 70th Scientific Sessions. The amount of iron consumed in the diet also was associated with an increased risk of heart attacks.
The researchers, led by professor Jukka T. Salonen, M.D., Ph.D., at the University of Kuopio, in Kuopio, Finland, found that men with the highest amounts of iron stored in their bodies had almost three-times the number of heart attacks than men with less iron in their blood and body.
Researchers say new studies looking at how lowering iron will affect heart disease is still needed to "ultimately verify or refute" the iron-coronary heart disease hypothesis. However, Salonen says, "We believe the current evidence, although still inconsistent, is strong enough to justify screening for high iron stores at least in high-risk persons."
The American Heart Association states that additional research is needed to prove iron's role in heart disease before screening can be recommended.
The possibility that increased iron stores heighten the risk of heart disease was first posed in the mid-1980s in a theory by South Carolina scientist Jerome L. Sullivan, M.D., Ph.D. In 1992 Salonen and his Kuopio colleagues reported the first study supporting Sullivan's theory. However, at least three groups of researchers in the United States failed to replicate the findings or explore other ways of testing Sullivan's theory. The U.S. scientists agreed that their studies were inconclusive.
In the latest study, Salonen and his team looked at 99 men who had suffered a heart attack during the last three to almost nine years, and 98 men who were healthy and who served as a "control group" for the study. The "control" group was among the 1,931 male participants in the on-going Kuopio Ischaemic Heart Disease Risk Factor Study who had no history of coronary heart disease, which causes heart attacks.
In their latest study being reported today, Salonen and his colleagues used a different technique to measure iron stores in the body.
"The technique is more specific, measuring the concentration of receptors that regulate the intake of iron into the body cells," Salonen says.
"Evidence concerning the role of body iron stores in coronary heart disease is inconsistent, due to inappropriate or unreliable measurements used in most previous studies."
The Finns measured the ratio of the transferrin receptors and ferritin, an iron-bearing protein that serves as the body's storehouse for iron. When body stores of iron increase, the receptors -- which act like a docking post for proteins -- "down-regulate" so that the cells are not overwhelmed with iron.
Thus, it's also important to include measurements of the iron receptors. Salonen says hematologists agree this procedure is the best noninvasive way to measure just how much iron is in the body.
The men with the lowest ratio of transferrin receptors to ferritin had the most iron in their body and the most risk of heart attack.
The technique allowed the researchers to eliminate other factors including inflammation in the risk analysis. The only other factor to show an association was increased iron intake from iron-rich food such as red meat.
Co-investigators are Tomi-Pekka Tuomainen, M.D.; Kari Punnonen, M.D., Ph.D.; and Kristiina Nyyssûnen Ph.D., all of the University of Kuopio.
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