Zhang 2015.

Study characteristics
Methods	Study design: Cluster‐randomised controlled trial Country: China Setting: Intervention conducted in nursing houses in northern China; outcomes measured in these nursing houses Aim of study: To observe the long‐term effect of consuming enriched potassium salt (KCl:NaCl = 1:1 by weight) on blood pressure, all‐cause mortality, target organ damage and safety in persons living in Chinese nursing houses. Unit of allocation: Nursing houses Start date: 2011 to 2012 End date: NR Relevant study limitations as reported by study authors: NR Sample size calculation: NR
Participants	Baseline Characteristics LSSS intervention Age: NR Gender: NR Ethnicity/race: Chinese Smoking: NR Body Mass Index (BMI): NR Blood pressure status: NR Antihypertensive medication used: NR Cardiovascular disease or stroke: NR Diabetes mellitus: NR Renal impairment: Serum creatinine in µmol/L, mean (SD): 69 (18.7) Dietary potassium intake: NR Dietary sodium intake: NR Urinary potassium excretion: in mmol/24 h, mean (SD): 25.4 (10.0) Urinary sodium excretion: NR Control Age: NR Gender: NR Ethnicity/race: Chinese Smoking: NR Body Mass Index (BMI): NR Blood pressure status: NR Antihypertensive medication used: NR Cardiovascular disease or stroke: NR Diabetes mellitus: NR Renal impairment: Serum creatinine in µmol/L, mean (SD): 69 (20.4) Dietary potassium intake: NR Dietary sodium intake: NR Urinary potassium excretion: NR Urinary sodium excretion: NR Overall Age: in years, mean: 65 Gender: NR Ethnicity/race: Chinese Smoking: NR Body Mass Index (BMI): NR Blood pressure status: NR Antihypertensive medication used: NR Cardiovascular disease or stroke: NR Diabetes mellitus: NR Renal impairment: NR Dietary potassium intake: NR Dietary sodium intake: NR Urinary potassium excretion: NR Urinary sodium excretion:NR Inclusion criteria: Clusters: nursing houses in the northern regions of China. Participants: inhabitants of nursing houses Exclusion criteria: None reported Pretreatment: No apparent imbalance Method of recruitment of participants: NR Informed consent obtained: NR Clusters: n = 30 clusters (number of participants NR); no details on whether analyses were adjusted for clustering Subgroups planned/measured: NR Subgroups reported: NR   Participant flow Assessed for eligibility: NR Excluded (number with reasons): NR Randomised: n = 30 clusters; number of participants NR Allocated to LSSS intervention(s): NR Allocated to control: NR Received allocated LSSS intervention(s): NR Did not receive allocated LSSS intervention(s): NR Lost to follow‐up (LSSS intervention group): NR Discontinued intervention (LSSS intervention group): NR Analysed (LSSS intervention group): n = 30 clusters at 3 to 5 months and 1 to 1.5 years, n = 22 clusters at 3 years, and n = 28 clusters at 4 years in total group (trial arm distribution NR); n = 1105 participants at 3 to 5 months and 1 to 1.5 years, n = 1032 at 3 years, and number of participants NR at 4 years Excluded from analysis (LSSS intervention group): NR Received allocated control: NR Did not receive allocated control: NR Lost to follow‐up (control group): NR Discontinued intervention (control group): NR Analysed (control group): n = 30 clusters at 3 to 5 months and 1 to 1.5 years, n = 22 clusters at 3 years, and n = 28 clusters at 4 years in total group (trial arm distribution NR); n = 947 participants at 3 to 5 months and 1 to 1.5 years, n = 807 at 3 years, and number of participants NR at 4 years Excluded from analysis (control group): NR
Interventions	Intervention Characteristics LSSS intervention Theoretical basis: Replacing regular salt with enriched potassium salt may have implications for blood pressure, safety, mortality and organ damage in older persons. Description: Enriched potassium salt (NaCl:KCl = 1:1) LSSS category: ≥ 30% KCl Contains fortificant: NR Delivery: discretionary use Duration of run‐in period: none Duration of active intervention: 4 years Duration of follow‐up (as reported): none Total duration of study (as reported): 4 years Timing: NR Implementation: 10 g/person/day dispensed to each nursing home every 3 months Providers: NR Co‐interventions: NR Resource requirements: NR Integrity of delivery: NR Control Theoretical basis: To enable comparison of LSSS intervention with standard practice Description: 'Normal' salt used Contains fortificant: NR Delivery: discretionary use Duration of run‐in period: none Duration of active intervention: 4 years Duration of follow‐up (as reported): none Total duration of study (as reported): 4 years Timing: NR Implementation: 10 g/person/day dispensed to each nursing home every 3 months Providers: NR Co‐interventions: NR Resource requirements: NR Integrity of delivery: NR
Outcomes	Primary outcomes:  Diastolic Blood Pressure (DBP): Outcome measurement: NR. Time points: 3 to 5 months, 1 to 1.5 years, 3, 4 years Systolic Blood Pressure (SBP): Outcome measurement: NR. Time points: 3 to 5 months, 1 to 1.5 years, 3, 4 years Hypertension (as reported, or SBP > 140 mmHg or DBP > 85 mmHg): NR Blood pressure control (achieving blood pressure threshold or 'control' as prespecified): NR Cardiovascular events‐stroke: NR Cardiovascular events‐myocardial infarction: NR Cardiovascular events‐other: NR Cardiovascular mortality: NR Blood potassium: Outcome measurement: NR. Time points: 3 to 5 months, 1 to 1.5 years, 4 years Hyperkalaemia: Outcome measurement: Defined as > 5.5 mmol/L. Time points: 1 to 1.5 years Hypokalaemia: NR Secondary outcomes:  All‐cause mortality: Outcome measurement: calculated by observed person‐years; time points: 3, 4 years Adverse events: NR Antihypertensive medication use: NR Body Mass index (BMI): NR Serum creatinine: Outcome measurement: NR. Time points: 3 to 5 months, 1 to 1.5 years, 4 years Albuminuria: Outcome measurement: Defined as ratio of microalbumin to creatinine ≥ 30 mg/g. Time points: 3 years Urinary albumin‐to‐creatinine ratio (uACR): NR Fasting blood glucose: NR Blood triglycerides: NR Total blood cholesterol: NR 24‐h Urinary sodium excretion: NR 24‐h Urinary potassium excretion: NR
Notes	Funding source: NR Authors name: Hongye Zhang Institution: Beijing Hypertension League Institute, Beijing, China Email: NR Possible conflicts of interest (for study authors): NR Sources used for data extraction: Conference abstract about the trial Trial registration details: NR
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information on how the randomisation sequence was generated
Allocation concealment (selection bias)	Unclear risk	No information on how the randomisation sequence was protected
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	There was no information available on whether participants and people delivering the intervention were blinded. Outcomes are objective and not likely to be affected by a lack of blinding, but modifications in behaviour due to awareness of assignment may have resulted in some performance bias.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Insufficient information available
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Insufficient information available
Selective reporting (reporting bias)	Unclear risk	No study protocol or prospective trial registry entry available
Other bias	Low risk	None identified
Recruitment bias (cluster‐RCTs)	Unclear risk	Insufficient information reported on whether clusters were identified before randomisation
Comparability with individually randomised trials (cluster‐RCTs)	Low risk	A previous RCT investigated the use of mineral salt with 10% potassium in middle‐aged and elderly Japanese and also found it to be a safe alternative to regular salt (Kawasaki 1998). This study also found a significant decrease in blood pressure in those consuming the mineral salt. Another RCT in older Dutch people found that replacing regular salt with low‐sodium high‐potassium salt led to blood pressure reduction in people with mild to moderate hypertension (Geleijnse 1994). A parallel‐design study (Zhou 2009) also reported similar reduction of blood pressure.
Loss of clusters (cluster‐RCTs)	High risk	A total of 27% (8/30) of clusters were not included in the analysis at year 3, and 7% (2/30) of clusters were not included in the analysis at year 4.
Baseline imbalance (cluster‐RCTs)	Unclear risk	Based on five baseline characteristics reported, there appeared to be no serious baseline imbalance initially; however, due to in‐ and out‐migration to and from the nursing homes, it was not clear whether baseline equivalence was maintained over time.
Incorrect analysis (cluster‐RCTs)	Unclear risk	Insufficient information on statistical analysis and adjustment for clustering in conference abstracts (full text not available)
Overall risk of bias	High risk	Unclear risk of bias for incomplete outcome data, recruitment bias and baseline imbalance; high risk for loss of clusters