EAL

NA: Effect on Blood Pressure (2009)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine if there is a relationship between elevated blood pressure in children and 24-hour urinary excretion of sodium and potassium and also determine if there is a relationship between blood pressure and dietary salt intake in children.

Inclusion Criteria:

Between six and 14 years of age
Current registration in a public school in the province of Almeria.

Exclusion Criteria:

Metabolic or chronic disease (liver disease, kidney disease, type I or II diabetes mellitus, hypopotassemia or hyperpotassemia
Pharmacological treatment during the previous three months with corticosteroids, insulin, diuretics, oral contraceptives or other drugs that could affect blood pressure values
Surgery or serious infectious disease during the previous six months
Children who were judged to be too agitated or nervous during the physical examination.

Description of Study Protocol:

Recruitment

Random sample of 613 children recruited from 107 public primary schools in the province of Almeria, southern Spain, for the school years 1993 to 1994.

Design

Parents completed a questionnaire regarding children's previous illnesses, pharmacological treatments, smoking and drug use and family history of diabetes, hypertension, hypercholesterolaemia, hypertriglyceridaemia, myocardial infarction, cerebrovascular disease, obesity, smoking and drug use. Each child underwent a physical exam to measure blood pressure (BP) and pulse (two determinations), body weight and height. A 24-hour urine sample was obtained from each child for analyses of sodium, potassium and creatinine concentrations.

Statistical Analysis

Student-Fischer T-tests were used to compare independent means for quantitative variables
Chi-squared tests were used to compare proportions
Pearson's linear correlation was calculated for bivariate quantitative variables with simple and multiple linear regression
All quantitative variables were analyzed with the Kolmogorov-Smirnoff test for normal distribution
The results for all quantitative variables are expressed as the mean ± standard deviation
Differences were considered statistically significant at P<0.05.

Data Collection Summary:

Timing of Measurements

One-time physical exam including BP and pulse (two determinations), body weight and height
One time 24-hour urine sample measuring sodium, potassium and creatinine concentrations.

Dependent Variables

Urinary excretion of sodium, potassium and creatinine, body weight and height, blood pressure and pulse.

Description of Actual Data Sample:

Initial N: N=553 (N=274 boys, N=279 girls)
Attrition (final N): N=553
Age: Between six to 14 years of age
Ethnicity: Spanish.

Anthropometrics

	Boys N=274	Girls N=279
Age (years)	10.3±2.6	10.4±2.5
Weight (kg)	41.8±14.2	40.6±12.6
BMI (kg/m²)	19.6±3.9	19.3±3.7

Location

Almeria, Spain.

Summary of Results:

Electrolyte Concentrations in a Sample of Spanish Schoolchildren Aged Six to 14 Years

	Boys, N=274	Girls, N=279	Overall, N=553
Na (mEq per 24 hours)	142.2±70.4	125.6±53.5*	136.3±63.3
K (mEq per 24 hours)	41.2±15.7	37.2±15.2 **	39.2±15.5
Creatinine (mg per 24 hours)	751.4±316.8	645.4±236.9*	697.9±281.4
SBP (mm Hg)	110.3±14.4	111.4±14.7	110.9±14.6
DBP (mm Hg)	60.6±9.5	61.6±9.2	61.1±9.4

SBP: Systolic blood pressure
DBP: Diastolic blood pressure
* P<0.001
** P< 0.01

Other Findings

BP found to be independent of sodium intake. Body weight correlated directly with both BP and sodium intake.

Author Conclusion:

Our findings are insufficient in themselves to justify the conclusion that there is no potential benefit in restricting dietary salt intake in children. Dietary habits at this age may lead to patterns of dietary behavior in adults that place them at increased risk of developing hypertension.

Funding Source:

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)	N/A
	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?	N/A
	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?	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?	N/A
	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?		Yes
	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?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	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?	Yes
	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?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	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?		Yes
	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?	Yes
	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?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	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?	Yes
	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?	N/A
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)?	No
	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?		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