Table 1. Behavioural science principles used in design.

Principle	Definition	Study implementation
Behavioural economics	The study of the psychological factors which influence how people make decisions, and how these decisions deviate from the implied rational approach.	The overarching discipline from which the principles below are drawn.
Status quo bias	The preference for maintaining one’s current situation or choosing inaction over action.	Opt-out language in messages—framing participation in the programme as the default choice.
Present bias	The tendency to give stronger weight to payoffs that are closer to the present time.11	Leveraged the dynamic of immediate rewards by (1) mailing a free BP monitor at enrolment and (2) providing a portion of US$200 incentive as soon as the participant agreed to participate. Effort reduction: BP measurement: mailed home monitor. Lipid testing: Pilot 1: given choice to complete phlebotomy at a local laboratory or have a phlebotomist come into home. Pilot 2: home self-test kit.
Norms of reciprocity	If you treat people nicely they will likely do the same.12	In addition to receiving a home BP monitor with enrolment, participants received a handwritten note welcoming them to the programme.
Social accountability	People try harder when they know their actions are observed by others.13	Let patients know that we will share updates with their PCP. Encouraged patients to tell a friend or family member about their goals and ask them to check-in.
Fresh starts	Individuals are more likely to engage when they perceive a blank slate and new opportunities.14	Framed the programme as a fresh start for patients who have been unable to lower their BP and cholesterol previously. Encouraged patients who were less engaged in sending BP data to view each reminder as a fresh start and provided them with additional days to meet the minimum BP requirement if needed.
Incentives	Something which motivates an individual to perform an action.	Provided a financial incentive, split as unconditional (after agreeing to participate, prior to any action) and conditional (contingent on completing the BP check and lipid panel).

BPblood pressurePCPPrimary care provider