EAL

NA: Effect on Blood Pressure (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine whether day-to-day changes in blood pressure (BP) are related with the daily variability of dietary balance of sodium (Na) and potassium (K). As the greater part of Na and K are excreted in the urine, the Na/K ratio in urine samples could represent the dietary balance of sodium and potassium.

Inclusion Criteria:

No inclusion criteria mentioned. However, subjects were:

Healthy men employed at the medical school
Did not use anti-hypertensive medications
Had BMIs less than 25.

Exclusion Criteria:

Authors did not specify.

Description of Study Protocol:

Recruitment: Men employed at the medical school
Design: Case report
Statistical Analysis: T-test using the NAP statistical package.

Data Collection Summary:

Timing of Measurements: Samples obtained for 11 to 33 days, either successively or intermittently
Dependent Variables: Concentrations of NA and K in urine were measured with a flame spectrophotometer (Corning: Model 480)
Independent Variables: BP measured with mercury sphygmomanometer. BP at point of disappearance of Korotkoff sounds (point V) was used for diastolic BP.
Control Variables:
- Age
- Height
- Weight.

Description of Actual Data Sample:

Initial N: Eight males
Attrition (final N): Eight males
Age: 28 years to 50 years
Ethnicity: Japanese
Other relevant demographics: Employees of the medical school
Anthropometrics (e.g., were groups same or different on important measures):
- Five of eight subjects had a family history of hypertension, i.e., at least one parent diagnosed as hypertensive
- No changes in weight observed during study period
- All subjects had BMIs less than 25Kg/m²
- Age of six subjects was 28 years to 34 years, one subject was 40 years of age and one was 50 years of age.
Location: Tohoku University School of Medicine, Sendai, Japan.

Summary of Results:

Mean SBP from 107.1 to 157.2mmHg; SD from 5.18 to 7.25mmHg; CV 3.3% to 5.8% for all eight subjects
Mean DBP from 64.4 to 97.2mmHg; SD from 4.19 to 8.55mmHg; CV 5.1% to 11.8% for all eight subjects.

Urinary Na/K Ratio

Geometric mean from 2.53 to 3.97; SD from 1.30 to 1.65; CV 30% to 65% for seven subjects
Geometric mean of 6.54; SD 1.52; CV 52% in other subject (Subject one).

Relationship of Urinary Na/K Ratio to BP

Correlation Coefficient (r) to SBP ranged from -0.11 to 0.70 in all eight subjects, but was only significant in Subject one (measured for 11 days) at 0.70 (P<0.05) and Subject two (measured for 33 days) at 0.45 (P<0.01)
R to DBP ranged from -0.24 to 0.72 in all eight subjects, but was only significant in Subject one at 0.72 (P<0.05)
Both Subjects One and Two had a family history of hypertension, however association between a family history of hypertension and a positive response of BP to urinary Na/K ratio was not significant (Fisher's exact probability test; P=0.357).

Author Conclusion:

The results of the present study suggest that the measurement of urinary Na/K ratio may be beneficial for checking the daily balance of Na and K intake of hypertensive patients who need to restrict salt intake. The method of using spot urine tests is practical and also can be conducted on an outpatient basis. We recommend the use of urinary Na/K ratio as an indicator of Na and K balance for the management of blood pressure levels of susceptible hypertensives.

Funding Source:

Reviewer Comments:

Not a well-conducted study. Small sample size, big variation in ages of individuals, subjects were all males, subjects studied for various periods of time.

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)	???
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	No
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	???
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	N/A

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?	N/A
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	N/A
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		???
	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?	No
	2.2.	Were criteria applied equally to all study groups?	No
	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?	???
3.	Were study groups comparable?		No
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	???
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	No
	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?	N/A
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	N/A
	4.4.	Were reasons for withdrawals similar across groups?	N/A
	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?		???
	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.)	Yes
	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?		No
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	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?	N/A
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	N/A
	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?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	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?	No
	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?	Yes
	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)?	Yes
	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?		???
	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?	???
	10.2.	Was the study free from apparent conflict of interest?	Yes