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. 2022 Aug 10;2022(8):CD015207. doi: 10.1002/14651858.CD015207

Zhou 2009.

Study characteristics
Methods Study design: Randomised controlled trial
Study grouping: Parallel group
Country: China
Setting: Intervention conducted in rural households in the Hedong district, Tianjin; outcomes measured at participants' homes
Aim of study: To evaluate the safety and efficacy of Compound Ion Salt on blood pressure control in an aged population with high dietary salt intake
Unit of allocation: adults (aged 18 years or older)
Start date: September 2003
End date: May 2004
Relevant study limitations as reported by study authors: The single‐blinded design of the study may have resulted in systematic bias in blood pressure measurement; only aged people were included in the study due to their regularised work‐rest schedule and them taking most meals at home, thereby limiting generalisability; quantitative determination of salty flavour perception was not done, only flavour tests in a small population which found no difference in perceived taste between the intervention and control.
Sample size calculation: The sample size was calculated to detect a ≥ 8 mmHg difference in systolic blood pressure with 80% power and significance of 5% using a two‐tailed test.
Participants Baseline Characteristics
LSSS intervention (participants with normal blood pressure)

  • Age: in years, mean (SD): 68.1 (8.3)

  • Gender: Female, % (n/N): 50.9 (29/57)

  • Ethnicity/race: Han Chinese

  • Smoking: Current smoker, % (n/N): 21.1 (12/57); past smoker, % (n/N): 12.3 (7/57)

  • Body Mass Index (BMI): in kg/m2, mean (SD): 23.9 (3.2)

  • Blood pressure status: Participants with normal blood pressure, % (n/N): 100 (57/57)

  • Antihypertensive medication used: n/a

  • Cardiovascular disease or stroke: Heart attack or stroke in past 6 months, current angina pectoris or congestive heart failure, % (n/N): 0 (0/57)

  • Diabetes mellitus: % (n/N): 0 (0/57)

  • Renal impairment: Serum creatinine, in µmol/L, mean (SD): 75.6 (21.2)

  • Dietary potassium intake: NR

  • Dietary sodium intake: NR

  • Urinary potassium excretion: in mmol/24 h, mean (SD): 22.8 (7.15)

  • Urinary sodium excretion: in mmol/24 h, mean (SD): 237 (50.0)


Control (participants with normal blood pressure)

  • Age: in years, mean (SD): 65.4 (4.5)

  • Gender: Female, % (n/N): 55.4 (36/65)

  • Ethnicity/race: Han Chinese

  • Smoking: Current smoker, % (n/N): 24.6 (16/65); past smoker, % (n/N): 12.3 (8/65)

  • Body Mass Index (BMI): in kg/m2, mean (SD): 23.7 (3.3)

  • Blood pressure status: Participants with normal blood pressure, % (n/N): 100 (65/65)

  • Antihypertensive medication used: n/a

  • Cardiovascular disease or stroke: Heart attack or stroke in past 6 months, current angina pectoris or congestive heart failure, % (n/N): 0 (0/65)

  • Diabetes mellitus: % (n/N): 0 (0/65)

  • Renal impairment: Serum creatinine, in µmol/L, mean (SD): 77.5 (18.9)

  • Dietary potassium intake: NR

  • Dietary sodium intake: NR

  • Urinary potassium excretion: in mmol/24 h, mean (SD): 23.7 (7.81)

  • Urinary sodium excretion: in mmol/24 h, mean (SD): 239 (36.6)


LSSS intervention (participants with hypertension)

  • Age: in years, mean (SD): 67.5 (5.2)

  • Gender: Female, % (n/N): 56.5 (35/62)

  • Ethnicity/race: Han Chinese

  • Smoking: Current smoker, % (n/N): 21.0 (13/62); past smoker, % (n/N): 9.7 (6/62)

  • Body Mass Index (BMI): in kg/m2, mean (SD): 25.2 (3.5)

  • Blood pressure status: Mild or moderate hypertension, % (n/N): 100 (62/62)

  • Antihypertensive medication used: % (n/N): 53.2 (33/62)

  • Cardiovascular disease or stroke: Heart attack or stroke in past 6 months, current angina pectoris or congestive heart failure, % (n/N): 0 (0/62)

  • Diabetes mellitus: %, (n/N): 0 (0/62)

  • Renal impairment: Serum creatinine, in µmol/L, mean (SD): 78.5 (18.5)

  • Dietary sodium intake: NR

  • Urinary potassium excretion: in mmol/24 h, mean (SD): 23.5 (7.16)

  • Urinary sodium excretion: in mmol/24 h, mean (SD): 238 (38.5)


Control (participants with hypertension)

  • Age: in years, mean (SD): 65.7 (6.3)

  • Gender: Female, % (n/N): 57.8 (37/64)

  • Ethnicity/race: Han Chinese

  • Smoking: Current smoker, % (n/N): 23.4 (15/64); past smoker, % (n/N): 12.5 (8/64)

  • Body Mass Index (BMI): in kg/m2, mean (SD): 24.9 (3.7)

  • Blood pressure status: Mild or moderate hypertension, % (n/N): 100 (64/64)

  • Antihypertensive medication used: % (n/N): 54.7 (35/64)

  • Cardiovascular disease or stroke: Heart attack or stroke in past 6 months, current angina pectoris or congestive heart failure, % (n/N): 0 (0/64)

  • Diabetes mellitus: % (n/N): 0 (0/64)

  • Renal impairment: Serum creatinine, in µmol/L, mean (SD): 76.8 (19.0)

  • Dietary potassium intake: NR

  • Dietary sodium intake: NR

  • Urinary potassium excretion: in mmol/24 h, mean (SD): 24.6 (8.12)

  • Urinary sodium excretion: in mmol/24 h, mean (SD): 241 (46.2)


Inclusion criteria: Men and women, aged between 50 and 80, willing to undertake long‐term use of the intervention salt; with serum potassium < 5.5 mmol/L, and net increase of < 1.0 mmol/L for serum potassium at the end of the run‐in period
Exclusion criteria: Participants who ate more than one meal per week outside their homes; currently used potassium‐sparing medication/diuretics; already had a family member enrolled in the study; had a history of heart attack or stroke in the past six months, current angina pectoris, or congestive heart failure; had diabetes mellitus, serious mental or physical illnesses, malignancy, or secondary hypertension; or had impaired renal function
Pretreatment: None
Method of recruitment of participants: Han people from ten communities in the Hedong District, Tianjin were recruited.
Informed consent obtained: Yes, unclear whether written or oral
Clusters: n/a
Subgroups planned/measured: Participants with normal blood pressure and participants with hypertension
Subgroups reported: Participants with normal blood pressure and participants with hypertension
Participant flow
Assessed for eligibility: n = 264
Excluded (number with reasons): n = 16 (met exclusion criteria, < 5.5 mmol/L serum potassium or net change of <1.0 mmol/L serum potassium following run‐in)
Randomised: n = 248
Allocated to LSSS intervention(s): n = 119 (n = 62 participants with hypertension; n = 57 participants with normal blood pressure)
Allocated to control: n = 129 (n = 64 participants with hypertension; n = 65 participants with normal blood pressure)
Received allocated LSSS intervention(s): NR
Did not receive allocated LSSS intervention(s): NR
Lost to follow‐up (LSSS intervention group): n = 13 (n = 10 (n = 8 participants with hypertension; n = 2 participants with normal blood pressure) withdrew; n = 3 participants with normal blood pressure lost to contact)
Discontinued intervention (LSSS intervention group): n = 10 (n = 8 participants with hypertension; n = 2 participants with normal blood pressure)
Analysed (LSSS intervention group): n = 119 (intention‐to‐treat with baseline values carried forward); n = 62 (participants with hypertension) n = 57 (participants with normal blood pressure)
Excluded from analysis (LSSS intervention group): n = 0
Received allocated control: NR
Did not receive allocated control: NR
Lost to follow‐up (control group): n = 9 (n = 8 (n = 6 participants with hypertension; n = 2 participants with normal blood pressure) withdrew; n = 1 participants with normal blood pressure lost to contact)
Discontinued intervention (control group): n = 8 (n = 6 participants with hypertension; n = 2 participants with normal blood pressure)
Analysed (control group): n = 129 (intention‐to‐treat with baseline values carried forward)
Excluded from analysis (control group): n = 0
Interventions Intervention Characteristics
LSSS intervention

  • Theoretical basis: Salt restriction is an important approach in the prevention of hypertension.

  • Description: 'Compound ion' salt (CISalt) (65% NaCl, 30% KCl, 5% calcium salts)

  • LSSS category: ≥ 30% KCl

  • Contains fortificant: Folic acid (12 mg/kg)

  • Delivery: discretionary use

  • Duration of run‐in period: 4 weeks

  • Duration of active intervention: 6 months

  • Duration of follow‐up (as reported): none

  • Total duration of study (as reported): 6 months

  • Timing: LSSS to be used by the entire household for cooking and other purposes.

  • Implementation: LSSS was provided in 1 kg bags, at 3 kg per household per month.

  • Providers: LSSS was manufactured and packaged by Tianjin Kaifu S&T Development, supervised by the China National Center for Salt Product Quality Control. Details about persons delivering the intervention not reported

  • Co‐interventions: NR

  • Resource requirements: NR

  • Integrity of delivery: Older persons were recruited, due to their regularised work‐rest schedules and predominant in‐home eating habits. The authors reported that compliance was attained over the course of the study.


Control

  • Theoretical basis: To enable comparison of LSSS intervention with standard practice

  • Description: 'Normal' salt

  • Contains fortificant: NR

  • Delivery: discretionary use

  • Duration of run‐in period: 4 weeks

  • Duration of active intervention: 6 months

  • Duration of follow‐up (as reported): none

  • Total duration of study (as reported): 6 months

  • Timing: Normal salt to be used by the entire household for cooking and other purposes.

  • Implementation: Normal salt was provided in 1 kg bags, at 3 kg per household per month.

  • Providers: Normal salt was manufactured and packaged by Tianjin Kaifu S&T Development, supervised by the China National Center for Salt Product Quality Control. Details about persons delivering the intervention not reported

  • Co‐interventions: NR

  • Resource requirements: NR

  • Integrity of delivery: Older persons were recruited, due to their regularised work‐rest schedules and predominant in‐home eating habits. The authors reported that compliance was attained over the course of the study.
Outcomes Primary outcomes: 

  • Diastolic Blood Pressure (DBP): Outcome measurement: Measurements performed in each participant's home using the auscultatory method by 2 experienced physicians. Time points: 2, 4, 6 months

  • Systolic Blood Pressure (SBP): Outcome measurement: Measurements performed in each participant's home using the auscultatory method by 2 experienced physicians. Time points: 2, 4, 6 months

  • 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: Adverse cardiovascular events; Outcome measurement: NR. Time points: duration of study

  • Cardiovascular mortality: NR

  • Blood potassium: NR

  • Hyperkalaemia: NR

  • Hypokalaemia: NR


Secondary outcomes:

  • All‐cause mortality: NR

  • Adverse events: NR

  • Antihypertensive medication use: NR

  • Body Mass index (BMI): NR

  • Serum creatinine: NR

  • Albuminuria: NR

  • Urinary albumin‐to‐creatinine ratio (uACR): NR

  • Fasting blood glucose: Outcome measurement: Determined from venous blood samples drawn after overnight fasting using biochemical assay. Time points: 6 months

  • Blood triglycerides: Outcome measurement: Determined from venous blood samples drawn after overnight fasting using biochemical assay. Time points: 6 months

  • Total blood cholesterol: Outcome measurement: Determined from venous blood samples drawn after overnight fasting using biochemical assay. Time points: 6 months

  • 24‐h urinary sodium excretion: 24‐hour urine sample. Time points: 6 months

  • 24‐h urinary potassium excretion: 24‐hour urine sample. Time points: 6 months
Notes Funding source: NR
Authors name: Xin Zhou and Yu‐Ming Li
Institution: Institute of Cardiovascular Disease and Division of Cardiology, Pingjin Hospital, Medical College of the Chinese People's Armed Police Forces, Tianjin
Email: cardiolab@gmail.com
Possible conflicts of interest (for study authors): None
Sources used for data extraction: Journal article of meeting report, with results of the trial
Trial registration details: NR
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Randomisation was done using a computer‐generated random sequence.
Allocation concealment (selection bias) Low risk Randomisation sequence numbers were placed in sealed envelopes. Intervention and control bags were manufactured by a supplier and only identified with the randomisation sequence.
Blinding of participants and personnel (performance bias)
All outcomes Low risk Participants were blinded to assignment; no information on whether people delivering the intervention were blinded. Given that participants were blinded and minimal interventionist involvement was reported, the study is not likely to be prone to performance bias.
Blinding of outcome assessment (detection bias)
All outcomes Low risk Outcome assessors were not blinded. Outcomes which may be prone to detection bias, e.g. auscultatory determination of blood pressure, were done by two experienced physicians. Other outcomes were not prone to detection bias as they were laboratory‐determined, or self‐reported by blinded participants.
Incomplete outcome data (attrition bias)
All outcomes Low risk Overall attrition was 22/248 (9%), with 13/248 (5%) in the intervention and 9/248 (4%) in the control group; and similar reasons for dropouts reported per group.
Selective reporting (reporting bias) Unclear risk No study protocol or prospectively trial registry entry available
Other bias Low risk None identified
Overall risk of bias Low risk Low risk of bias for allocation concealment and incomplete outcome data