Community Hypertension Control Using the Health Belief Model and PRECEDE-PROCEED

Plain-language summary

This protocol describes a community-based cluster randomized controlled trial in Kamalgonj Upazila, Moulvibazar district, Bangladesh, evaluating a theory-driven intervention to improve blood pressure (BP) control among adults with hypertension. The intervention is grounded in the Health Belief Model (HBM) and structured using the PRECEDE-PROCEED framework to address behavioural and structural barriers such as poor medication adherence, high salt intake, physical inactivity, inadequate fruit intake, tobacco use, fragmented care and limited access to affordable medicines. Formative mixed-methods research in the study communities showed high levels of uncontrolled hypertension despite treatment, frequent non-adherence, unhealthy diet and activity patterns, heavy smokeless tobacco use and reliance on informal providers. These findings informed the PRECEDE phases (social, epidemiological, behavioural/environmental, educational/ecological and administrative/policy assessments) and the selection of intervention targets. Twelve clusters (villages or wards of about 3,000-5,000 residents) will be randomised 1:1 to intervention or control, with around 40 participants per cluster (≈480 in total). Adults are eligible if they are ≥18 years, have physician-diagnosed hypertension or BP ≥140/90 mmHg on two occasions, have lived in the cluster ≥6 months and can provide informed consent; exclusions include severe comorbidities requiring intensive care, severe cognitive impairment and pregnancy or planned pregnancy within 12 months. Randomisation is stratified by urban/rural status and performed by an independent statistician, with outcome assessors and data analysts blinded where feasible. The sample size was calculated to detect a 5-7 mmHg difference in mean systolic BP at 12 months with 80% power, assuming a standard deviation of 20 mmHg, intracluster correlation of 0.02-0.05 and up to 15% loss to follow-up. The intervention consists of four components delivered over 12 months by trained community health workers. Group education includes four bi-weekly 45-60-minute sessions on understanding hypertension, benefits of BP control, practical medication-adherence strategies and lifestyle modification (salt reduction, physical activity, healthy eating and tobacco cessation), using interactive methods and local success stories to influence perceived threat, benefits, barriers, cues to action and self-efficacy. Individual counselling and motivational interviewing (two one-to-one sessions at weeks 4 and 8) identify personal barriers, set SMART goals and build confidence for daily self-management. Enabling strategies include community BP monitoring corners equipped with automated devices, reminder calendars with tick-boxes, pictorial Bengali leaflets on low-salt recipes and exercise, wallet cards summarising key messages, and linkages to affordable generic antihypertensives and government essential drug programmes, including collaboration with local pharmacy sellers and village doctors where feasible. Reinforcing strategies involve inviting family members to at least one group session, monthly follow-up calls or home visits from months 3-12 to provide encouragement and problem-solving, facilitation of informal peer support or walking groups, and public recognition or certificates for participants who achieve BP control or sustained behaviour change. Control clusters receive usual care without structured HBM-based education or community follow-up, and will be offered a condensed version of the intervention after 12-month follow-up. Data are collected at baseline, 6 months and 12 months. Primary outcomes are change in mean systolic BP from baseline to 12 months and the proportion of participants with controlled BP (systolic \<140 mmHg and diastolic \<90 mmHg) at 12 months. Secondary outcomes include change in mean diastolic BP, BP control at 6 months, HBM construct scores, medication adherence measured with the Bangladesh Medication Adherence Scale, lifestyle behaviours (salt intake, physical activity, fruit and vegetable consumption, tobacco use), knowledge of hypertension and health-service utilisation (clinic visits, BP monitoring frequency and source of BP checks). BP is measured by trained data collectors using validated automated oscillometric devices following WHO/ISH guidelines, with two seated readings averaged at each visit. Process evaluation will assess fidelity, reach, dose, acceptability and contamination using attendance registers, facilitator checklists, supervision forms, questionnaires and qualitative interviews. Impact evaluation will examine changes in HBM constructs, adherence, behaviours, knowledge and service use at 6 and 12 months, while outcome

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