Mobile Cued Adherence Therapy (mCAT) for Blood Pressure Medication

The investigators will use Medicaid's prescription data to construct the Primary Outcome of AH medication adherence using the date and supply of pills for each new prescription or refill to determine the number of days in a month a client had pills available. Since refills are often made before an existing prescription ends, the supply of new medications will be counted on days following the last available dose of the prior prescription. The number of days with available AH medication(s) will be divided by the total number of days in the same month to calculate the proportion of days covered (PDC), which will range from 0 and 1.

All participants will be asked to submit blood pressure readings for seven consecutive days after baseline activities, and be reminded via SMS and email to submit readings after the 4-month intervention and again after the month 8, 12, and 24 assessments. The investigators will calculate the Primary Outcome measure of blood pressure as participants' mean and coefficient of variation in systolic and diastolic blood pressure over the seven-day interval.

The investigators will use Medicaid's encounters and reimbursement costs data to construct our Secondary Outcomes of healthcare utilization and costs. The investigators will generate separate monthly measures of the number of unique encounters, as well as the number of days in an emergency department, and inpatient and outpatient healthcare settings. Since a single encounter can be billed multiple times (thus appearing multiple times in the data) or last multiple days, the investigators will remove duplicate encounter claims based on the date of service, diagnostic codes, and procedure costs associated with each encounter. The investigators will separately measure the monthly AHCCCS reimbursement costs for all unique encounters in each healthcare setting.

Habit strength (i.e., behavioral automaticity) will be measured using the Self-Reported Behavioral Automaticity Index (SRBAI), a frequently used 4-item subscale of the Self-Reported Habit Index (SRHI). The SRBAI assesses the degree to which a given behavior (e.g., pill taking) is an automatic or unconscious process. Scores range from 5-20, with higher scores indicating greater self-reported habit strength

This is an objective measure of habit strength that will provide an estimate of the monthly proportion of days with cued pill-taking. Specifically, the investigators will estimate the monthly proportion of days with a valid cue check-in (i.e., containing photographic evidence of a participant's contextual cue) that is successfully submitted within +/- 1 hour of the stated time when the participant's cue occurs during the day. This proportion will range from 0 to 1, where a higher proportion indicates greater habit strength.

Present bias (i.e., the tendency for monetary rewards now to be valued higher relative to those at any future point) will be measured using the Multiple Price List Task, which asks participants to choose between smaller rewards received sooner and larger rewards received later. This is estimated by comparing participants' willingness to forego rewards received today versus future periods, relative to their willingness to forego rewards received in two weeks versus points after two weeks. A person's willingness to forego rewards today relative to forgoing rewards in two weeks for future rewards indicates their degree of present bias.