This study is not a randomized clinical trial nor is it a observational cohort. This study utilizes a computer-simulated cohort called a “Markov” cohort. “Markov” chains are named after Andrey Markov and are commonly used for statistical modeling in finance, economics, social sciences, physics and medicine. Bibbins-Domingo utilized the Coronary Heart Disease (CHD) model which has been used to describe trends in CHD and the effects of interventions intended to reduce the risk of CHD and cost associated with treating CHD. This model inputs known data in regards to most accurate epidemiological data in the US (census, death rates, CHD rates, heath care expenditure, risk reduction estimates etc.) into a complex “Markov” chain to determine the cardiovascular and economic benefit of reducing the salt consumptions by 3 grams per day.
Reducing the number of new cases/year of
- Coronary heart disease (CHD) by 60,000 to 120,000
- Stroke by 32,000 to 66,000 (750,000 per year in US)
- Myocardial infarction by 54,000to 99,000 (1.25 million per year in US)
Save 194,000 to 392,000 quality-adjusted life-years
Save $10 billion to $24 billion in health care costs annually
The results of this “study” are provocative and intriguing. Would this “Markov” cohort play off as predicted in the “Real” world? If so, the reduction of 3 grams of sodium from the diet would have a huge economic and medical impact. These efforts would be akin to weight reduction and smoking cessation initiatives. Even if this reduction of sodium intake was only by 1 gram per day we would likely see huge benefits. However, achieving salt reduction will be a major feat. Lowering salt intake would require change on two important fronts; the public policy approach and the individual approach. The later will likely prove to be the most difficult to curtail as the “salt appetite” of the US population is increasingly fed with processed food products. An interesting editorial exploring this phenomenon by Philip Klemmer appeared in the April 2010 AJKD entitled “salt appetite”. He subjected himself (and several UNC renal fellows) to an extremely low salt diet. Being from North Carolina myself I know first hand that this is an extremely difficult task. They each had an average drop in weight of 1.4 kg with a drop in blood pressure. The group finished the “experiment” and went back to their normal eating habits. Salt has endured as an important part of our culture. The word “salary” was used to describe how Roman soldiers were paid for their duties with salt. Salt was used as a way to preserve foods before the widespread use of refrigerators, but its usage has persisted and has perhaps grown in popularity.
For now, recommending a low salt diet is an important part of blood pressure control. But, one can argue that this is an important part of each of our diets. We will see how the public policy debate plays out in this “great salt war”. Any decrease in “added” salt to food will be a welcomed improvement. Curtailing the “salt appetite” will likely prove to be more challenging than any spirited political debate.