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HTN: Vitamins (2007)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To assess the effect of long-term (three months) supplementation of vitamin E on clinic and 24-hour ambultory systolic and diastolic BP in treated hypertensive patients.
Inclusion Criteria:
  • Subjects were at least 50 years old and at high-risk for CVD, due to at least one CVD risk factor, including arterial hypertension
  • Hypertension was defined as at least 160/95mm Hg on three seperate visits or on antihypertensive drug treatment.
Exclusion Criteria:
  • Interruption of trial treatment
  • Did not perform ambulatory BP monitoring
  • Changed antihypertensive drug therapy.
Description of Study Protocol:


Recruitment
  • In the framework of the Primary Prevention Project, Italy
  • Enrolled through 15 hypertension units.

Design

  • Subjects were randomized to one of four treatment groups:
    • Aspirin (100mg qd)
    • Vitamin E (300mg qd)
    • Aspirin plus vitamin E
    • No treatment.
  • Baseline measures of clinic and mean ambulatory BP monitoring were taken. Treatment was implemented for three months, followed by the same BP measures.
  • At baseline and three months later, the clinic BP was measured twice in the sitting position and the mean values were used. Each subject also underwent 24-hour ambulatory BP monitoring at baseline and at the three-month time point. The monitoring was done on a normal working day with readings every 15 minutes.

Blinding Used

None mentioned.

Intervention

Four randomized groups of intervention for 3 months:

  • Group One: Aspirin (100mg daily)
  • Group Two: Vitamin E (300mg daily)
  • Group Three: Aspirin plus vitamin E
  • Group Four: No treatment.
Statistical Analysis
  • Power test required at least 125 subjects in each group to ensure significance of 5% with 90% power
  • Differences from baseline were anayzed by Student's T-test and chi square test
  • Treatment effect was analyzed as a "within-subject" variable in an ANOVA model.
Data Collection Summary:

Timing of Measurements

At baseline and following three months of intervention.

Dependent Variables

  • Variable One: Clinic BP measured twice in a sitting position, with a mean of the two measures used
  • Variable Two: BP using 24-hour ambulatory blood pressure monitoring with readings every five minutes, using validated equipment (Takeda 2420 and 2421, Spacelab 90207, Accutracker II, Profilomat); mean systolic and diastolic values were used. 

Independent Variables

  • 300mg vitamin E
  • 100mg aspirin
  • Aspirin plus vitamin E.

Control Variables

None.
Description of Actual Data Sample:

 

Initial N

166.

Attrition (final N)

  • 142 (76 men, 66 women)
  • 75 subjects randomized to vitamin E
  • 67 subjects randomized to control (no intervention)
  • Five withdrew
  • 19 were excluded due to interrupted trial intervention, did not perform the ambulatory BP monitoring or changed antihypertensive drug therapy.

Age

Mean, 59±5.9 years.

Ethnicity

Not mentioned.

Other Relevant Demographics

None given.

Anthropometrics

None given.

Location

None given (assume Italy).

Summary of Results:

Variable

Baseline (x±SD)

Third Month (x±SD)

Change (±95% CI)

P-Value

Clinic systolic BP
Control
Vitamin E


144.5±15.2
147.4±16.1


140.6±16.7
139.1±17.2


-4.4 (-7.7/-1.1)
-7.8 (-10.9/-4.7)



0.15

Clinic diastolic BP
Control
Vitamin E


86.1±8.3
87.9±8.9


84.0±8.7
85.0±8.3


-2.6 (-4.4/-0.8)
-2.4 (-4.2/-0.6)



0.85

Mean 24-hour systolic BP
Control
Vitamin E


131.8±13.1
131.5±14.1


133.1±13.2
130.6±15.7


+1.3 (-1.2/+3.8)
-0.9(-3.3/+1.5)



0.20

Mean 24-hour diastolic BP
Control
Vitamin E


77.6±8.3
78.1±6.7


77.8±8.2
76.4±6.7


+0.2 (-1.2/+1.6)
-1.6 (-2.8/-0.4)

 

0.06

  • Change is change from baseline
  • Systolic and diastolic BP were similarly reduced for those randomized to vitamin E and no vitamin (control)
    The P-stastic reflects a comparison of change from baseline between the control and vitamin E supplemented groups. Thus, there were no differences between the groups.
  • There were no statistical differences from baseline in BP.
Author Conclusion:
  • No effect on clinic BP or 24-hour ambulatory BP was observed after three months of treatment with vitamin E in patients already being treated with antihpertensive drugs.
  • The authors mention that the subjects already had near-normal baseline BP while on drug treatment, so a change from baseline may have been difficult to ieffect with vitamin E
  • Another limitation was the population size of 142, rather than the desired 250.

 

Funding Source:
Industry:
Bayer Italia
Pharmaceutical/Dietary Supplement Company:
Reviewer Comments:
  • No controls for confounding factors such as stress, dietary intake, vitamin supplements, medications other than antihypertensives or physical activity
  • The type of vitamin E used is not described
  • Analysis for the vitamin E-supplemented subjects with and without aspirin is not given.
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) No
  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? No
2. Was the selection of study subjects/patients free from bias? No
  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? ???
  2.3. Were health, demographics, and other characteristics of subjects described? No
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) No
  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.) 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? No
  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.) ???
  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? Yes
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? No
  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? 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? No
  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? ???
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? ???
  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? No
  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? No
  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? 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? No
  8.1. Were statistical analyses adequately described and the results reported appropriately? No
  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)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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? Yes
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