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Sunday, December 01, 2002Two studies in Thursday's New England Journal of Medicine on the long-term effects of mercury exposure on the hearts of middle-aged and elderly men had opposite findings. One found no clear link between mercury levels in the body and the risk of developing heart disease; the other found men who had suffered a heart attack had higher mercury levels than similar men who had not. Here’s the study that claims an association between mercury levels and heart disease, and the accurate synopsis of it given by the article: Researchers at the Johns Hopkins Bloomberg School of Public Health reviewed data and tissue samples from an earlier, nine-country European cardiac study. They compared 684 middle-aged men who had had one heart attack with 724 similar men who had not had a heart attack. They looked at the men's health history, use of tobacco and alcohol, and toenail clippings and fat withdrawn from their buttocks. Toenails hold accumulated mercury, and fatty tissue accumulates DHA; their levels in each subject were measured. Those with the highest mercury levels were nearly 2.2 times more likely than those with the lowest levels to have had a heart attack, said Dr. Eliseo Guallar, assistant professor of epidemiology at Hopkins. That sounds impressive, but they only got that figure by playing with the numbers, or as they put it, “adjusting for age and center.” The truth is that for each center they looked at, the levels of mercury in heart attack patients and healthy people were practically the same. The mean levels differed anywhere from zero to 0.05 micrograms/gram. In two testing centers, the mean levels were the same in both patients and controls - Russia and the Netherlands. At all of the centers, the range of mercury levels in patients and controls overlapped more than they differed. It’s a stretch to say, as the authors do, that mercury is playing a role here in these heart attacks. What is obvious from their data, is that high blood pressure (26% of patients vs. 17% of controls) and smoking (61% vs. 37%), are playing a role. The other study made more of an effort to control for such variables. They matched patients with controls based on smoking habits and age. Even more notable, they had patients and controls with higher levels of mercury than the other study. The highest quintile in the first study had a mean mercury level of 0.66 micrograms/g. The highest quintile in the second had a mean level of 1.34 micrograms/g. (They think the levels were so high because they had a large number of dentists participating.) Yet there was still no association between heart attacks and lead levels : Researchers at Harvard School of Public Health studied 470 men who had had heart surgery or a heart attack, comparing each with a similar man without heart disease. Dr. Walter C. Willett, a professor of epidemiology and nutrition, said mercury levels in the men's toenails corresponded well with the levels of fish they reported eating, but his team found no association between mercury exposure and risk of heart disease. I’d say it’s safe to say, based on both studies, there’s no association between mercury exposure and heart disease. posted by Sydney on 12/01/2002 06:16:00 AM 0 comments 0 Comments: |
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