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Trial registered on ANZCTR


Registration number
ACTRN12613000514707
Ethics application status
Approved
Date submitted
6/05/2013
Date registered
9/05/2013
Date last updated
12/01/2016
Type of registration
Retrospectively registered

Titles & IDs
Public title
Effects of vitamin C and grape-seed polyphenols on blood pressure in treated hypertensive individuals
Scientific title
Effects of vitamin C and grape-seed polyphenols on blood pressure in treated hypertensive individuals
Secondary ID [1] 282455 0
Nil
Universal Trial Number (UTN)
N/A
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Hypertension 289067 0
Condition category
Condition code
Diet and Nutrition 289408 289408 0 0
Other diet and nutrition disorders
Cardiovascular 289409 289409 0 0
Hypertension

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
Following a 3-week run-in period (during which tea and coffee intake was limited to 3 cups per day and all red wine was ceased), subjects were allocated to a study treatment via block randomization using computer-generated random numbers, devised by the statistician. Volunteers were assigned to receive either (1) 500 mg/day vitamin C and matched grape-seed polyphenol placebo, (2) 1000 mg/day grape-seed polyphenols and matched vitamin C placebo, (3) 500 mg/day vitamin C and 1000 mg/day grape-seed polyphenols, or (4) matched placebo tablets for both grape-seed polyphenols and vitamin C. Participants took assigned tablets during a 6 week intervention period in a double-blind fashion. Tablets were taken twice daily at meal times as 250 mg and 500 mg of vitamin C and polyphenols,
respectively. All tablets were identical in appearance, size. All study personnel and participants were blinded to treatment assignment for the duration of the study. Outcome measurements were performed at the end of the run-in period (baseline) and again at the end of the 6 week intervention period.
Intervention code [1] 287100 0
Treatment: Other
Comparator / control treatment
Matched placebo tablets for both grape-seed polyphenols (plant cellulose) and vitamin C (plant cellulose) for 6 weeks. Oral tablets were taken twice daily at meal times as 250 mg and 500 mg of vitamin C placebo and polyphenol placebo, respectively.
Control group
Placebo

Outcomes
Primary outcome [1] 289518 0
Blood pressure

Blood pressure was assessed as 24 h ambulatory blood pressure with blood pressure and heart rate measured every 20 min during the day time and every 30 min at night time. Ambulatory blood pressurewas assessed by a trained researcher who fitted a Spacelabs monitor (Spacelabs Medical Inc. Redmond, WA, USA) and explained its use to the participants. The monitor was fitted to the non-dominant arm approximately 2.5 cm above the antecubital fossa. Participants were instructed to continue their usual daily activities and to avoid any vigorous exercise. Measurements showing an error code or those with a pulse pressure of less than 20 mm Hg were excluded from the analysis. Blood pressure traces were considered complete if more than 80% of the recordings were valid.
Timepoint [1] 289518 0
6 weeks

At 6 weeks from start of treatment.
Secondary outcome [1] 302666 0
Rate of blood pressure variation

Within-visit rate of variation of systolic and diastolic blood pressure, pulse pressure and heart rate were calculated for day time (08:00–20:00) and night time (22:00-06:00) periods from the 24 h ambulatory blood pressure traces. The within-visit rate of measurement-to-measurement blood pressure and heart rate variation was calculated using the slope of the change in systolic blood pressure, diastolic blood pressure, pulse pressure and heart rate between each reading over time.
Timepoint [1] 302666 0
6 weeks

At 6 weeks from start of treatment.

Eligibility
Key inclusion criteria
All individuals were taking one or more antihypertensive drugs for  3 months, had a mean 24-h ambulatory systolic BP of  125 mmHg and at least one additional cardiovascular disease (CVD) risk factor. Risk factors included previous coronary or cerebrovascular event > 6 months, hyperlipidaemia (total cholesterol > 6 mmol/l), use of lipid-lowering therapy, or smoking > 5 cigarettes/day. All volunteers ceased any vitamin, fish oil or antioxidant supplements for at least 3 weeks prior to study entry. All usual medication was taken as prescribed on the morning of each visit and maintained for the duration of the trial.
Minimum age
21 Years
Maximum age
75 Years
Sex
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
Exclusion criteria included: previous coronary or cerebrovascular event  6 months, heart failure or unstable disease, premenopausal, use of nitrate medication, use of oral contraceptive, body mass index > 35 kg/m2, diabetes mellitus, fasting glucose 7 mmol/l, or elevated serum creatinine (men > 110 mmol/l or women > 100 mmol/l). Individuals were asked to limit tea and coffee intake to 3 cups/day, and cease all red wine and commercial fruit juice for the duration of the study.

Study design
Purpose of the study
Treatment
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
All study personnel and participants were blinded to treatment assignment for the duration of the study. Tablets were were visually identical and were placed into bottles labelled A to D. The chief investigator held the code for the tablets in a sealed envelope which was not broken until the end of the trial.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Participants were allocated to a study treatment via block randomization, using computer-generated random numbers (generated by a biostatistician who was not involved in the conduct of the study) sealed in opaque envelopes.
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
Intervention assignment
Factorial
Other design features
Phase
Not Applicable
Type of endpoint/s
Efficacy
Statistical methods / analysis
Sample size was calculated using blood pressure as the primary endpoint. 16 participants in each group provided more than 80% power to detect a 5 mm Hg difference in systolic blood pressure (alpha=0.05).

Outcome variables were analysed using linear mixed models Fixed effects included baseline value, visit (baseline or post), treatment group, hour and treatment group X hour.

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
1/02/2002
Date of last participant enrolment
Anticipated
Actual
30/05/2003
Date of last data collection
Anticipated
Actual
Sample size
Target
74
Accrual to date
Final
74
Recruitment in Australia
Recruitment state(s)
WA

Funding & Sponsors
Funding source category [1] 287241 0
Government body
Name [1] 287241 0
National Health and Medical Research Council
Country [1] 287241 0
Australia
Primary sponsor type
University
Name
The University of Western Australia
Address
The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009
Country
Australia
Secondary sponsor category [1] 285993 0
None
Name [1] 285993 0
Address [1] 285993 0
Country [1] 285993 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 289220 0
Royal Perth Hospital Human Ethics Committee
Ethics committee address [1] 289220 0
Ethics committee country [1] 289220 0
Australia
Date submitted for ethics approval [1] 289220 0
Approval date [1] 289220 0
21/11/2000
Ethics approval number [1] 289220 0
EC2000/055

Summary
Brief summary
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 39822 0
Dr Natalie Ward
Address 39822 0
UWA School of Medicine and Pharmacology, GPO Box X2213, Perth, WA 6847
Country 39822 0
Australia
Phone 39822 0
+61 (0)8 9224 0391
Fax 39822 0
+61 (0)8 9224 0246
Email 39822 0
Natalie.Ward@uwa.edu.au
Contact person for public queries
Name 39823 0
Natalie Ward
Address 39823 0
UWA School of Medicine and Pharmacology, GPO Box X2213, Perth, WA 6847
Country 39823 0
Australia
Phone 39823 0
+61 (0)8 9224 0391
Fax 39823 0
+61 (0)8 9224 0246
Email 39823 0
Natalie.Ward@uwa.edu.au
Contact person for scientific queries
Name 39824 0
Natalie Ward
Address 39824 0
UWA School of Medicine and Pharmacology, GPO Box X2213, Perth, WA 6847
Country 39824 0
Australia
Phone 39824 0
+61 (0)8 9224 0391
Fax 39824 0
+61 (0)8 9224 0246
Email 39824 0
Natalie.Ward@uwa.edu.au

No information has been provided regarding IPD availability


What supporting documents are/will be available?

No Supporting Document Provided



Results publications and other study-related documents

Documents added manually
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Documents added automatically
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