IMPACT OF EXPANDING THE NATIONAL SALT REDUCTION INITIATIVE: A MATHEMATICAL MODEL OF BENEFITS AND RISKS OF POPULATION-LEVEL SODIUM REDUCTION

Purpose:

The Institute of Medicine has identified reducing sodium intake as a priority for reducing cardiovascular disease (CVD), but has also noted that the risk of very low sodium intake also exists for subgroups of the US population. A key question is what conditions are necessary such that expansion of the National Salt Reduction Initiative (NSRI), in which food producers agree to lower sodium levels in processed food products, would significantly reduce hypertension and associated CVD in the US population while minimizing potential perversities such as excessively low sodium intake among vulnerable groups. 

Method:

We linked data on sodium reduction levels in food categories included in the NSRI to 24-hour dietary recalls from a nationally-representative sample of Americans completing the National Health and Nutrition Examination Survey (2003-2010). We input these linked data into a stochastic microsimulation model of hypertension, myocardial infarction (MI) and stroke morbidity and mortality to assess how variations in dietary intake and dietary responses to sodium reduction of NSRI foods would be expected to alter disease risk, incorporating variations in the blood pressure response to sodium intake among different demographic groups. Sensitivity analyses were conducted to assess whether variations in how food producers and consumers respond to sodium reduction initiatives could alter the benefits and risks of the NSRI.

Result:

Expansion of the NSRI to include all major manufactured and restaurant food products would be expected to avert 5.4% (95% CI, 5.2 to 5.5) of MIs and 6.2% (95% CI, 6.0 to 6.4) of strokes per year over the next decade. An 8% greater reduction in sodium intake was observed from achieving sodium content to NSRI targets in packaged foods than in restaurant foods. High levels of consumer addition of table salt or substitution of higher sodium products were found to be unlikely to neutralize this benefit. However, older women were found to be at potential risk of increased mortality from excessively low sodium intake, if recent epidemiological associations between low sodium and increased mortality are indeed causal.

Conclusion:

Expanding the NSRI is expected to significantly reduce hypertension and hypertension-related CVD morbidity and mortality among the majority of the population, even in the context of compensatory consumer behaviors. But older women in particularly may be at risk for excessively low sodium intake.