Hypertension

HTN: Medical Nutrition Therapy (2015)

Citation:

Darne B, Nivarong M, Tugaye A, Safar M, Plouin PF, Guillanneuf MT, Cubeau J, Pannier B, Peguignot F, Cambien F. Hypocaloric diet and antihypertensive drug treatment. A randomized controlled clinical trial. Blood Press. 1993; 2(2): 130-135. 

PubMed ID: 8180725
 
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 compare the amount of drugs quantified by a score model needed to control blood pressure in two groups of overweight hypertensive patients, receiving or not receiving a hypocaloric diet.

Inclusion Criteria:

Pre-inclusion

  • Patients between 18 and 70 years of age
  • Above 110% overweight
  • Mild to moderate hypertension
  • Receiving no antihypertensive drug or from whom antihypertensive drug treatment could be withdrawn.

Inclusion

  • Mean diastolic blood pressure between 95 to 110mm Hg of three measurements 
  • No anti-hypertensive drug treatment for at least three weeks prior to visit.
Exclusion Criteria:
  • Systolic blood pressure greater than or equal to 200mm Hg
  • Treated diabetes mellitus or fasting plasma glucose greater than or equal to 7.7mmol per L
  • Serum cholesterol level more than eight mmol per L
  • History of allergy to sulfamid
  • Planned or present pregnancy
  • Reporting an efficient hypocaloric diet, i.e., having lost two kg in the previous two months.

 

Description of Study Protocol:

Recruitment

Recruitment methods were not described.

Design

Randomized controlled clinical trial. Subjects were randomly assigned to drug treatment or hypocaloric diet. Randomization was stratified on hospital and sex. 

Intervention

  • Drug treatment: Antihypertensive drug was administered. Subjects were followed for 10 months by clinician only
  • Hypocaloric diet: Subjects were highly incited to accept a hypocaloric diet and were told that if their blood pressure could not be normalized with diet after two months, an antihypertensive drug would be administered to the subjects with a diastolic blood pressure more than 90mm Hg, following the same protocol as in the drug treatment group. Subjects were followed for 10 months by a clinician and a dietitian.

Statistical Analysis

  • Percentages and means were compared between groups
  • For quantitative variables, the means of the variation between inclusion and after 10 months were compared between the two groups after adjustment on center and sex
  • Both intra- and inter-group comparisons were performed.
Data Collection Summary:

Timing of Measurements

At the inclusion visit, subjects were interviewed about their usual nutritional intake and had blood samples drawn. Subjects were seen after one, two, four, six, eight and 10 months for anthropometric and blood pressure measurements. At the last consultation, every subject of each group was interviewed by the dietitian about his or her nutritional intake and had blood samples drawn.

Dependent Variables

  • Score of treatment: Hydrochlorothiazide 25mg (score=1), with, as needed to obtain a diastolic blood pressure less than 90mm Hg, the addition of enalapril 10mg (score=2), 20mg (score=3) and nifedipine 40mg (score=4) 
  • Weight measured in light clothing
  • Body circumferences measured at right arm, waist and hips
  • Height  
  • Blood pressure measured with sphygmomanometer
  • Fasting blood sample analyzed for sodium, potassium, urea, creatinine, glucose, insulin, triglycerides, cholesterol, HDL-cholesterol, uric acid, protids, calcium and hematocrit
  • Electrocardiogram and X-ray.

Independent Variables

  • Drug treatment
  • Hypocaloric diet.

Control Variables

  • Center
  • Sex.
Description of Actual Data Sample:
  • Initial N: 54 subjects (22 women, 32 men)
  • Attrition (final N): 48 subjects; five dropped out of the hypocaloric diet group (two for non-compliance to diet, three unknown reasons) and one dropped out of the drug treatment group (unknown reason)
  • Age: Mean age 47±9 in drug treatment group, 50±9 in hypocaloric diet group
  • Anthropometrics: Blood pressure was slightly higher in the hypocaloric diet group, and heart rate was faster in the drug treatment group
  • Location: Two hospital outpatient hypertension clinics in France.

 

Summary of Results:

 

Variables

Change in Drug Treatment Group (N=27)

Change in Hypocaloric Diet Group (N=21)

Statistical Significance of Group Difference

Weight (kg)

-2.3±3.8 -5.9±5.4 P=0.011

BMI

-0.78±1.34

-2.17±1.93

P<0.05 

Waist to hip ratio -18±16 -23±11 NS 
SBP (mm Hg) -15±8 -18±7 NS
DBP (mm Hg) 6±12 6±8 NS
Heart rate (rate per minute) -10±16 -14±19 NS

Other Findings

Mean weight loss was 5.9±1.2kg in the hypocaloric diet and 2.3±0.7kg in the drug treatment group (P=0.02).

Mean decrease in diastolic blood pressure was 18±7mm Hg in the hypocaloric diet and 15±8mm Hg in the drug treatment group (P=0.36).

Mean diastolic blood pressure was 84±7.8mm Hg in the hypocaloric diet group and 85±7.2mm Hg in the drug treatment group.

In the hypocaloric diet group, eight (38.1%) subjects had a diastolic blood pressure less than 90mm Hg without any drug treatment.

The mean drug treatment score was 0.86±0.91 in the hypocaloric diet and 1.52±0.70 in the drug treatment group (P=0.01).   

Author Conclusion:

This study shows that in overweight hypertensives, the quantity of drug needed to achieve an acceptable level of blood pressure is nearly reduced by 50% when an efficient hypocaloric diet is prescribed simultaneously. Further studies are needed to estimate the mechanism underlying the decrease in blood pressure with weight reduction, and to establish the factors predictive of the normalization of blood pressure with weight reduction alone.

Funding Source:
Reviewer Comments:

Recruitment methods were not described. Groups had significant differences at baseline.

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? No
  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? No
  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? ???
  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? 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? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
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