Minimum effective dose of a multicomponent behaviour change intervention to increase the physical activity of individuals on primary statin therapy: an adaptive study using the time-to-event continual reassessment method (TiTE-CRM)

Abstract

Objectives: To identify the minimum effective dose of a multi-behaviour change technique (BCT) intervention to increase physical activity among individuals on primary statin therapy using the time-to-event continual reassessment method (TiTE-CRM).

Setting: A large New York metropolitan area healthcare system comprising approximately 85 000 employees and 5.5 million patient encounters annually.

Participants: 42 participants enrolled in 13 cohorts of 3 participants, 1 cohort of 2 participants and 1 cohort of 1 participant. The sample was composed of 16.7% individuals aged 66 and older (n=7), 64.3% women (n=27), 69.0% white individuals (n=29) and 7.1% Hispanic individuals (n=3).

Interventions: A variable-duration, four-BCT text message intervention and a 2-week follow-up. Dose assignment relied on TiTE-CRM to adjust the duration of the intervention based on adherence of participants in prior cohorts. Five mechanisms of action (MoAs) were assessed: self-efficacy, intrinsic regulation, discrepancy in behaviour, motivation and barriers to activity.

Primary and secondary outcome measures: The primary outcome measure was the proportion of participants who achieved a 2000 step/day increase between baseline and follow-up. The secondary outcomes were within-participant changes in daily steps (examined as a continuous variable at the daily level) and potential MoAs for increased physical activity.

Results: Of the 40 participants who completed follow-up, 7 (17.5%) achieved the goal of 2000 or more steps per day during their follow-up period. Though participants did increase the number of steps they walked during the intervention (B(SE)=373.1 (154.7) steps; p=0.016), there was no association between increased intervention duration and increased daily average steps. The intervention was also associated with increases in self-efficacy (p=0.002), intrinsic regulation (p=0.037), discrepancy in behaviour (p<0.001) and motivation (p=0.039).

Conclusions: The results of this trial did not show a traditional dose-response curve to increasing the length of a multicomponent BCT intervention. Results did show that the intervention successfully increased steps during the intervention period and that the benefit of the intervention dwindled during follow-up. Further, potential MoAs for the intervention were confirmed.

Trial registration number: NCT05273723.

Keywords: Behavior; Cardiovascular Disease; Physical Fitness.

Figure 1. Participant enrolment diagram.

Figure 2. Visualisations of participant step counts over time. Participant daily step counts at baseline seemed to be strongly associated with step counts during follow-up (upper left panel). In addition, baseline step counts did not appear to be strongly associated with change in steps between baseline and follow-up (upper right panel). Examining the association between intervention duration (ie, intervention dose) and change in steps between baseline and follow-up did not appear to show a dose-response increase (lower left and lower right panels; green indicates baseline and follow-up and red indicates intervention).