Digital Nudges to Improve Heart Health Actions After Community Screening in Malaysia (NADI-MyHeartRisk)

Cardiovascular disease remains a major cause of preventable morbidity and mortality. Community-based cardiovascular risk screening can identify individuals at increased risk, but risk awareness alone may not lead to preventive action. This study evaluates whether a personalised digital behavioural-nudge pathway delivered after MyHeartRisk community screening can improve completion of risk-appropriate cardiovascular preventive actions within 90 days. This is a pragmatic, risk-stratified, individually randomized, 2-group parallel controlled trial nested within routine NADI centre operations across Malaysia. Adults attending participating NADI centres will undergo MyHeartRisk cardiovascular risk screening. MyHeartRisk is a web-based cardiovascular risk assessment and risk communication platform used by trained NADI staff. Participants will be classified as low, moderate/intermediate, or high cardiovascular risk using the Framingham Risk Score-based trial classification. All screened participants will receive their MyHeartRisk result, standard risk explanation and general heart-health education. Participants classified as high cardiovascular risk will also receive a MyHeartRisk referral letter advising healthcare provider review. Participants classified as low cardiovascular risk will not be randomized and will not contribute to the primary randomized effectiveness analysis. They may be followed descriptively as part of the implementation cohort. Participants classified as moderate/intermediate or high cardiovascular risk will be randomized after risk classification and standard baseline risk feedback. Randomization will be performed centrally by the MyHeartRisk platform using a computer-generated allocation sequence. Allocation will be 1:1 between the personalised digital nudge arm and the no-nudge control arm. Randomization will be stratified by risk category and, where technically feasible, by NADI centre or region. If centre-level stratification is not feasible because of small numbers per centre, randomization will be stratified by risk category, with NADI centre included as a random effect in the analysis. The target enrollment for the randomized trial component is 848 moderate/intermediate- or high-risk participants, allocated 1:1 to the personalised digital nudge arm and the no-nudge control arm. This enrollment target refers to the randomized trial population, not the wider NADI screening cohort. The wider NADI programme provides the operational screening pool from which eligible participants are identified. Across 1,098 NADI centres, the minimum operational target is one participant per centre per month over six months, giving 6,588 screened participants. Where feasible, centres may screen up to two participants per month, giving a stretch operational target of 13,176 screened participants. Low-risk participants may be followed descriptively but will not be included in the primary randomized analysis. Participants in the personalised digital nudge arm will receive standard baseline care plus automated, risk-specific WhatsApp messages over 90 days. The intervention is grounded in the Behaviour Change Wheel and COM-B model. Messages are designed to support psychological capability through clear risk explanation and actionable next steps, opportunity through scheduled prompts and referral support, and motivation through engagement check-ins, reminders, action-planning prompts and barrier-solving messages. Active nudge contacts are scheduled in four structured cycles at Day 3, Day 5, Day 7, Day 14, Day 16, Day 18, Day 45, Day 47, Day 49, Day 60, Day 62, and Day 64. Participants in the no-nudge control arm will receive standard baseline care only. This includes MyHeartRisk risk feedback, standard risk explanation, general heart-health education and referral letter generation for high-risk participants. They will not receive scheduled behavioural nudges, personalised prompts, action-planning messages, reminder messages or barrier-check messages during the 90-day follow-up period. No clinically indicated advice, referral or follow-up normally available outside the study is withheld from any participant in either arm, and participants may seek care at any time. Both arms will receive neutral, standardized outcome-assessment messages at Day 30 and Day 90. These assessment messages are used for data collection only and will not contain behavioural advice, referral reminders, encouragement or personalised prompts. This is intended to reduce measurement bias and preserve the no-nudge comparison. The primary outcome is completion of a prespecified, risk-appropriate cardiovascular preventive action within 90 days among randomized moderate/intermediate- and high-risk participants. For moderate/intermediate-risk participants, this includes completion of cardiovascular preventive health checks, such as blood pressure, glucose or lipid assessment, medication review, or healthcare provider review. For high-risk participants, this is attendance at a healthcare provider within 90 days after MyHeartRisk screening and referral letter generation. Only actions that take place after the MyHeartRisk screening visit count; measurements taken at the screening visit itself are excluded. Outcome completion will be assessed using a pragmatic verification hierarchy that includes documentary evidence, healthcare provider or study-staff confirmation, participant self-report with supporting details, and participant self-report without supporting details. Submitting documentary evidence is optional, only the date, facility and action type are recorded, and declining does not affect participation. The primary analysis will follow the intention-to-treat principle and will use mixed-effects regression models accounting for centre-level clustering.