EAL

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To evaluate the effect of no added salt diet on a hypertensive population with high dietary sodium intake by measuring 24-hour urinary sodium excretion as an index of the effectiveness of this regimen on restriction of sodium intake.

Inclusion Criteria:

Mild to moderate hypertension
Not on any anti-hypertension medication
Healthy control.

Exclusion Criteria:

Healthy controls who did not match for age and gender.

Description of Study Protocol:

Recruitment

Random selection from outpatient clinic at Shiraz University from those who referred with mild to moderate hypertension and not on anti-hypertensive medication. Controls were selected randomly from among healthy subjects referring for annual check-ups.

Design

Non-randomized controlled trial.

Intervention

No-added-salt diet or DASH diet for six weeks followed by cases only.

Statistical Analysis

Mann-Whitney U-test.

Data Collection Summary:

Timing of Measurements

Baseline and after six weeks:

A 24-hour Holter monitoring and 24-hour urinary sodium excretion
Weekly assessment of dietary intake.

Dependent Variables

Salt intake: Qualitative evaluation of routine weekly food intake
Systolic and diastolic blood pressure: A 24-hour Holter monitor
Urinary sodium excretion: A 24-hour collection.

Independent Variables

No-added-salt diet or DASH diet.

Control Variables

Controls matched for sex and age.

Description of Actual Data Sample:

Initial N: N=80 (60 case, 20 control), with 40 males (30 case) and 40 females (30 case)
Attrition (final N): Not given; assuming 80
Age: Ages 48.7 years (case) and 46.1 years (control): P=0.41
Other relevant demographics: Smoking was more common in the control group, with 25% vs. 5%.

Anthropometrics

No statistically significant differences for age, weight, sex, hyperlipidemia and family history of hypertension between the two groups. Mean systolic blood pressure and diastolic blood pressure and mean urinary sodium excretion was not statistically different between the groups.

SBP (day):
- Case: 147.1±12.7
- Control: 141.2±10.2
- P=0.06.
SBP (night):
- Case: 136.7±9.2
- Control: 133.3±10.9
- P=0.173.
Urinary Na excretion (24-hour):
- Case: 132mEq (35mEq to 200mEq) per dL
- Control: 216mEq (210mEq to 274mEq) per dL
- P=0.42.

Location

Iran.

Summary of Results:

Key Findings

Variables	Treatment Group Differences Between Pre-treatment and Post-treatment Mean±SD	Control group Differences Between Pre-treatment and Post-treatment Mean±SD	Statistical Significance of Group Difference
Systolic BP (day)	12.1±9.2	-4.9±6.6	P=0.001
Systolic BP (night)	11.13±9.8	-1.1±3.9	P=0.001
Diastolic BP (day)	6.8±7.3	-2.4±3.3	P=0.01
Diastolic BP (night)	5.9±4.8	-1.1±3.7	P=0.001
24-hour Urinary Na excretion(mEq per dL) (MEDIAN)	42 (-100 to 110)	-4 (-69 to 23)	P=0.001

Other Findings

Pre-intervention urinary sodium excretion median was 132mEq (35mEq to 200mEq) per dL for cases and 216mEq (210mEq to 274mEq) for controls (P=0.42) and post-intervention excretion was 110mEq (50mEq to 174mEq) per dL for cases and 200mEq (178mEq to 279mEq) dL for controls (P=0.01)
A total of 35% of patients reached the urinary sodium excretion level less than 100mEq per dL in 24 hours after six weeks of the diet (prior to diet was 8%, P=0.0001)
Decrease in systolic blood pressure at night to more than 15% (night dipping of pressure) was not statistically significantly increased after six weeks of no added salt (P=0.241).

Author Conclusion:

Despite modest effect on dietary sodium restriction, the no-added-salt diet significantly decreased systolic blood pressure and diastolic blood pressure; it should be advised to every hypertensive patient.

Funding Source:

University/Hospital:

Shiraz University

Reviewer Comments:

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		Yes
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	Yes
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	N/A
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		No
	4.1.	Were follow-up methods described and the same for all groups?	No
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		N/A
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	N/A
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	N/A
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	N/A
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	N/A
	6.6.	Were extra or unplanned treatments described?	N/A
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	N/A
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		Yes
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	N/A
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes