Hypertension

HTN: Medical Nutrition Therapy (2015)

Citation:

Koopman H, Spreeuwenberg C, Westerman RF, Donker AJM. Dietary treatment of patients with mild to moderate hypertension in a general practice: A pilot intervention study. (1) The first three months.  Journal of Human Hypertension. 1990; 4: 368-371.

PubMed ID: 2258876
 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To study the effects of intensive dietary counseling on blood pressure and answer the questions:

  • What is the overall effect of advice based on a combination of the different recommended measures?
  • What is the best strategy for the general practitioner, dietitian and practice nurse to bring about considerable changes in nutritional habits?
Inclusion Criteria:
  • Mild to moderate hypertension: Diastolic blood pressure between 90 to 110mm Hg on three different occasions
  • No impairment in renal function
  • No use of antihypertensive drugs during at least six weeks prior to the trial
  • No use of oral contraceptives
  • BMI of not more than 27
  • No history of insulin-dependent diabetes mellitus or coronary heart disease.
Exclusion Criteria:
  • Diastolic blood pressured above 110mm Hg on three occasions
  • Increase in body weight of 5% above baseline level
  • Signs and symptoms of coronary heart disease.
Description of Study Protocol:

Recruitment

During routine consultations, patients were asked to participate in the study if they met inclusion criteria.

Design

Randomized controlled trial. 

Intervention

  • Subjects were randomized into dietary advice or control group for one year, but only the first three months are reported
  • Dietary advice subjects were sent to the dietitian, the control group had to wait three months before seeing the dietitian
  • The dietary advice group visited the dietitian monthly for dietary recall, explanation of the principles of the desired diet, weight control and individual feedback
  • Diet was of a composition considered to be appropriate and was monitored by a dietitian, with the goal intake of 85 to 100mmol sodium, 76 to 100mmol potassium, 25 to 30mmol calcium, 20mmol magnesium, 10% to 12% of energy from polyunsaturated fatty acids, and 30g nutritional fibers.

Statistical Analysis

Student's T-test with 95% (90% one-tailed) confidence intervals were used for statistical analysis.

Data Collection Summary:

Timing of Measurements

Patients were asked to return to the practice each fortnight for six weeks for history taking and measuring of blood pressure.

Dependent Variables

  • Systolic and diastolic blood pressure using sphygmomanometer
  • Mean arterial pressure
  • Serum lipids: Total cholesterol, HDL cholesterol, triglycerides
  • Change in calculated LDL-cholesterol
  • Change in sodium excretion in 24 hours, corrected for creatinine excretion. 

Independent Variables

Dietary advice or control group for one year, but only the first three months are reported.

 

 

Description of Actual Data Sample:
  • Initial N: 35 subjects, 17 in dietary advice (eight men, nine women) and 18 in control group (eight men, 10 women)
  • Attrition (final N): 30 subjects (86% completion); two subjects from dietary advice preferred to use hypotensive drugs. In the control group, two subjects had suspected angina and one had diastolic blood pressure of more than 110mm Hg on three occasions.
  • Age: Mean age 44±7 years in dietary advice, 46±9 years in control group
  • Anthropometrics: Differences between groups at baseline were not statistically significant
  • Location: The Netherlands.

 

Summary of Results:

 

Variables

Change in Dietary Advice Group in Three Months (N=15) Change in Control Group in Three Months (N=15)

Change Between Groups After Three Months

SBP (mm Hg)

-3.2, P=0.08 -0.4, P=0.4 2.8, P=0.17
DBP (mm Hg) -3.1, P=0.03 -1.1, P=0.2 2.0, P=0.15
Mean Arterial Pressure (mm Hg) -3.1, P=0.05 -0.9, P=0.2 2.2, P=0.13
Sodium Excretion (mmol per 24 hours) -20.6, P=0.04 1.6, P=0.4 22.2, P=0.07

LDL-cholesterol (mmol per L)

0.4, P=0.004

0.3, P=0.025

0.7, P=0.001

Other Findings

Statistically significant decreases in diastolic blood pressure, mean arterial pressure, sodium excretion and LDL-cholesterol occurred in the intervention group, although differences in change between the intervention group and control group, except for LDL-cholesterol, were not statistically significant. 

Author Conclusion:

It was not clear whether and to what extent change in the diet was responsible for the lowering of blood pressure in the intervention group. We could not prove statistically that the achieved change of diet was responsible for the lowering of blood pressure in the intervention group. 

Funding Source:
Reviewer Comments:

Small numbers of subjects in groups. Authors note that because of the small number of patients involved, conclusions should be drawn with caution.

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? ???
  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? ???
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.) ???
  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? ???
  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? ???
  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? No
  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? 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? Yes
  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? ???
  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)? ???
  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? No
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? No
  10.2. Was the study free from apparent conflict of interest? Yes