Using a low-sodium, high-potassium salt substitute to reduce blood pressure among Tibetans with high blood pressure: a patient-blinded randomized controlled trial.

To evaluate the effects of a low-sodium and high-potassium salt-substitute on lowering blood pressure (BP) among Tibetans living at high altitude (4300 meters).The study was a patient-blinded randomized controlled trial conducted between February and May 2009 in Dangxiong County, Tibetan Autonomous Region, China. A total of 282 Tibetans aged 40 or older with known hypertension (systolic BP≥140 mmHg) were recruited and randomized to intervention (salt-substitute, 65% sodium chloride, 25% potassium chloride and 10% magnesium sulfate) or control (100% sodium chloride) in a 1: 1 allocation ratio with three months' supply. Primary outcome was defined as the change in BP levels measured from baseline to followed-up with an automated sphygmomanometer. Per protocol (PP) and intention to treat (ITT) analyses were conducted.After the three months' intervention period, the net reduction in SBP/DBP in the intervention group in comparison to the control group was -8.2/-3.4 mmHg (all p<0.05) in PP analysis, after adjusting for baseline BP and other variables. ITT analysis showed the net reduction in SBP/DBP at -7.6/-3.5 mmHg with multiple imputations (all p<0.05). Furthermore, the whole distribution of blood pressure showed an overall decline in SBP/DBP and the proportion of patients with BP under control (SBP/DBP