Prediction of response to sodium intervention for blood pressure control

Abstract

In the Dietary Intervention Study of Hypertension (DISH) we found that patients formerly treated with drugs and assigned to sodium-reduction intervention were twice as likely to remain off medication for up to 56 weeks as were the controls assigned to no-diet intervention, after adjusting for covariates. Within the sodium-restriction group approximately 60% of 131 people were Intervention Successes (IS) (urinary sodium less than or equal to 100 mmol/day at 8 weeks). The rest were classed as Non-Intervention Successes (NIS). Of the IS group, 54% were responders (drug-free for at least 56 weeks), but about 56% of the NIS group also remained drug-free. Multiple logistics showed that no one factor was able to predict response among the IS. We conclude that the IS likely to respond to sodium reduction are not readily identifiable a priori. Furthermore, since both IS and NIS showed similar blood-pressure effects from the sodium-restriction regimen compared with controls, the questions arise: whether a factor other than sodium reduction affects the blood pressure response for the sodium-restriction group; or whether the measurement of sodium intake and excretion is sufficiently precise to distinguish compliers from non-compliers.