The JAMA Study on Low Sodium Risk: A Clue From China

Murray Epstein, MD; Jiguang Wang, MD, PhD


August 19, 2011

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Murray Epstein, MD: You have just heard an excellent presentation by Dr. Wang. We are now in New York at the American Society of Hypertension's annual meeting, and we have been fortunate enough to invite Dr. Wang to join us today to discuss specific aspects of hypertension in China. What I would like to do is to focus on one your comments [about] one of the aspects that you highlighted as an example, the issue of sodium, and the elevated sodium intake in the Chinese population [with hypertension].

The focus on the fairly dramatic differences in diet, I think are worthy of discussion, higher sodium and low dietary potassium. Let me perhaps start off with the sodium issue. As you know very well as a leader in hypertension, there has been some controversy in that, with Graham Macgregor on the one hand, Larry Apel here in the United States, and Mickey Alderman on the other, and how important that is. The controversy was enlivened, at least in the media, very recently when your good friend and colleague, and former mentor Jan Staessen[1] of Leuven, published a very provocative article in JAMA on the European Project on Genes in Hypertension (EPOGH) study.[2] Without further belaboring that, let me ask you what your thoughts are and how that interpretation of the data would fit in with what you presented this morning on hypertension in China.

Jiguang Wang, MD, PhD: Jan Staessen is a very good friend of mine and has also been my scientific mentor for so many years. He always does excellent research, and actually I was, I probably still am, a part of the EPOGH study, which is a multinational European study, including Belgium, Italy, Poland, the Czech Republic, and in the beginning, also Bulgaria and Romania. This is a European-funded study, a very nice study, and the recent publication is indeed, very provocative.

Dr. Epstein: Just to interrupt you for a second, just encapsulate in one sentence, what the major finding was in terms of correlation of death with the lower sodium.

Dr. Wang: They did an analysis looking at the relationship between urinary sodium excretion and mortality, and they had very different findings if you compare them with some others. They found that patients with a lower urinary sodium excretion actually had higher mortality, meaning that population recommendations for sodium restriction could be important, but for some people it could be detrimental if we believe in this study. From my point of view, this research is important, but probably conditional.

If we look at the data from Europe and China and compare these 2 populations, we find a very big difference in potassium intake, with a similar amount of urinary sodium excretion. When you have a high potassium intake, probably potassium is a kind of an antagonist for sodium, and you would not see a very big negative influence of sodium [in Europe]. However, in China, where the dietary potassium intake is low, sodium intake could be very important, not only for blood pressure, but also for stroke incidence and mortality.

In the Chinese population, when the potassium is low, if you have higher dietary sodium intake, you would have a very big risk, which is probably quite different if we compare this observation with the European study.

Dr. Epstein: I think that's very important -- the notion that it is not as simplistic as the media would have led us to believe, and that there are confounders and qualifiers that have to be considered as well.

In summary, I would like to thank Dr. Wang for having joined us this morning, and for having shared with us his expertise, his views, his vision going forward of hypertension in China. I think many of the attributes that we have heard this morning clearly differ somewhat from the phenotype, if you will, of hypertension here in the United States and in Western Europe, and they basically provide a platform for considering both future studies and rational treatment paradigms in the management of hypertension. Again, Dr. Wang, thank you so much for accepting our inviiation and for traveling from Shanghai to join us this morning on the day after the convening of the American Society of Hypertension annual meeting.

Dr. Wang: Thank you very much, Murray. It's a pleasure for me to be here.