Measuring Individual Responses to a Wholegrains and Nuts Intervention to Reduce Blood Pressure in Prehypertension
Condition: Prehypertension
MeSH terms: Prehypertension
Study type: Interventional

Summary: 
      The aim of the study is to investigate whether physiological, psychological and environmental
      factors, at an individual level, modify a) adherence, and b) blood pressure response, to a
      nuts and wholegrains intervention in participants at risk for developing high blood pressure.
      For 24 weeks, participants will, on a daily basis, monitor their own blood pressure using a
      wireless blood pressure monitor and respond to short semi-personalised questionnaires using a
      wrist-worn device, which also measures activity levels. Participants will receive an
      intervention of wholegrain foods and nuts to substitute into their diets for 8 weeks, between
      two 8-week observation periods. The length of the study periods will enable repeated
      measurements to be taken, in order to assess what factors, on an individual level, are
      associated with fluctuations in the outcomes. This will provide an insight into the types of
      factors that can help to explain individual fluctuations in adherence and physiological
      outcomes, such as blood pressure, that are common in nutrition studies. In the future, this
      should help in tailoring the way the investigators deliver effective individualised
      interventions, and enable researchers to be better able to consider and control for factors
      that can affect adherence and response to dietary interventions.
    

Detailed description: 
      The study will be conducted as an interventional N-of-1 study with an A1-B-A2 design of 8
      weeks per study period. Prior to the study, participants will be screened and if eligible,
      will complete a number of baseline questionnaires to provide an overview of their typical
      eating and lifestyle-related behaviours, and general health. A second visit prior to the
      start of the study will then be arranged, where participants will undergo a semi-structured
      interview. Responses from the interview, in combination with their baseline questionnaire
      responses, will be used to identify factors specific to the participant that show some degree
      of variability. These will form the basis of the semi-personalised questionnaires delivered
      via the wrist-worn PRO-Diary device for the duration of the study. During the study,
      participants will visit the institute in a fasted state every 4 weeks (7 visits total), in
      order to provide a blood sample for assessment of cholesterol levels and for assessment of
      biomarkers of wholegrains intake. At the first visit, participants will receive the wireless
      blood pressure monitor and PRO-Diary wrist device programmed with twice-daily questionnaires
      at times convenient to the participant. After 2 weeks and every 4 weeks thereafter,
      participants will be sent a link by email to complete a 24-hour dietary recall. After 8
      weeks, participants will begin the intervention phase and receive wholegrains equivalent to 3
      portions a day and 1 portion of unsalted nuts per day for the following 8 weeks. Participants
      will be able to choose from a variety of wholegrain products commonly available at
      supermarkets. They will also receive dietary advice to follow a Dietary Approaches to Stop
      Hypertension (DASH) diet aimed at lowering blood pressure. All other measures will continue
      as previously. At week 16, the wholegrains and nuts will be withdrawn and participants will
      be followed up for a further 8 weeks. At their final visit to the institute, they will
      complete the same validated questionnaires as at baseline. Results from the study will be
      analysed using N-of-1 dynamic modelling to analyse trends over time and determine whether any
      personalised factors significantly affected adherence to intervention or blood pressure
      response.
    

Intervention name(s): Dietary intervention: nuts and wholegrains with dietary advice for a blood-pressure lowering diet
Intervention type(s): Other
Intervention description(s): 30g mixed unsalted tree nuts (almonds, hazelnuts and almonds) per day; 3 portions of wholegrain foods per day (including wholegrain cereal products, wholegrain bread and wholegrain pasta); guidance for following the Dietary Approaches to Stop Hypertension (DASH) diet
Intervention model: Single Group Assignment
Intervention model description: This is a series of N-of-1 studies where data from each participant will be analysed separately. Each study follows an A1-B-A2 design consisting of an initial observation phase, an intervention phase and a follow-up phase, each of 8 weeks duration.
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: N-of-1; Ecological Momentary Assessment; Blood pressure; Whole grains; Nuts