Methods	Individual RCT
Participants	N Randomised: 2382 (1191 intervention; 1191 control) Baseline Blood Pressure: Int: mean SBP 127.5 (SD 6.6), DBP mean 86.0 (SD 1.9); Ctrl: SBP mean 127.4 (SD 6.2), DBP SD 85.9 (SD 1.9) Case mix: Normotensives Age: Int.: mean 43.9 (SD 6.2); Ctrl.: mean 43.3 (SD 6.1) CV diagnoses: None Percentage male: 65.7% Percentage white: 79.3% Inclusion/exclusion criteria: Inclusion: 30-54 year old adults with no evidence of medically diagnosed hypertension who were moderately overweight (men: between 26.1-37.4kg/m2; women: between 24.4-37.4kg/m2), and had average DBP between 83-89mmHg, and an SBP <140mmHg. Participants also had to demonstrate compliance with the more difficult data collection tasks Exclusion: Evidence of current hypertension. History of CVD, diabetes mellitus, malignancy other than nonmelanoma skin cancer during the past 5yrs, or any other serious life-threatening illness that requires regular medical treatment. Current use of prescription medications that affect BP, as well as non-prescription diuretics. Serum creatinine level >= 1.7mg/dL for men or 1.5mg/dL for women, or casual serum glucose >=200mg/dL. Current alcohol intake >21 drinks/wk. Pregnancy, or intent to become pregnant during the study. Plans to move or inability to cooperate
Interventions	Intervention Total duration: 36 mths Salt reduction/advice component: Individual and weekly group counselling sessions were provided initially followed by additional less intensive counselling and support for the remainder of follow-up. Mini-modules to reinforce the content of the counselling session were offered in the later years of the intervention. The content of sessions included sodium information, self-management and social support components. Sessions were provided by registered dieticians mainly, plus a few psychologists, or other experienced counsellors. The objective was to reduce urinary sodium excretion in the intervention group to 80mmol/24h Other: The salt reduction intervention was combined with a weight loss intervention or alone Comparator Dietary: No advice Other: Usual care or weight loss intervention alone.
Outcomes	All cause mortality CV morbidity (a composite of myocardial infarction, stroke, coronary revascularisation or CV death), BP, urinary excretion
Follow up	36 mths
Country & setting	US - 9 clinics
Notes	This study had a 2×2 factorial design in which the groups were: weight loss alone, sodium reduction alone, a combination of weight loss and sodium reduction, and a usual care group. The long term effects of the sodium reduction intervention were analysed by grouping data for the two sodium reduction interventions (alone or with weight loss) and for the two non-sodium reduction groups (usual care and weight loss alone)
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not reported
Allocation concealment (selection bias)	Low risk	“The clinic then notified the coordinating center [of participant eligibility] by telephone and obtained a randomisation assignment. In those cases where random assignment was not done by phone, clinics also were provided with sealed randomization envelopes for use when contact with the coordinating center was not possible. ”
Blinding (performance bias and detection bias) All outcomes	Low risk	“With respect to the determination of categorical end points, in order to minimize bias in the ascertainment of hypertension, an Endpoints Subcommittee conducts a blind review of study forms, and as necessary, the medical records of participants who are considered to have had hypertensive events. Potential hypertensive end points identified are either confirmed or refuted by the subcommittee. ” “[Data collectors] were masked to participants’ intervention assignments. ” No - participants; Yes - data collectors; Unclear - data analysts
Incomplete outcome data (attrition bias) All outcomes	Low risk	“For those with BP measurements but without urinary sodium excretion data at the corresponding follow-up visit, a 0 change in urinary sodium excretion was imputed in a secondary analysis. ” “For the small number of participants with no useable BP readings after randomisation (n=99, of whom 57% were treated early with BP medications by their physicians), measures from a randomly selected participant in the usual care group were imputed under the assumption that having little or no exposure to the intervention programs would produce similar results to that of the usual care group. ”
Selective reporting (reporting bias)	Low risk	All outcomes described in methods are reported in results.
Assessment of compliance?	Low risk	“Intervention attendance also is collected for participants within each of the active intervention groups. The dietary data are collected on random samples of equal numbers of participants across the treatment groups. The 24-hour urine specimens for sodium, potassium and creatinine measurements are collected from all participants at 18 and 36 months. An additional 24-hour urine specimen, collected on a 25% sample of trial participants at 6 months, was added to more fully assess sodium intakes at this time as compared to baseline levels. ” “Urinary sodium excretion and weight change are collected as intermediate end points for all participants. These intermediate end points were selected to evaluate compliance to specific interventions ”
Groups balanced at baseline?	Low risk	“Baseline characteristics were evenly distributed, except for age, which was higher in the sodium reduction intervention group”
Intention to treat analysis?	Low risk	“In a sensitivity analysis using logistic regression we performed an intention to treat analysis treating non-responders as non-events. Because mortality follow-up was virtually complete, we included all randomised participants in analyses of mortality alone in a full intention to treat analysis. ”
Free from follow up bias?	Unclear risk	Longest event follow up for mortality and CV morbidity was ~8years but last stated diet advice stated as 36 months. No urinary sodium excretion data available at longest follow up