A BCT Intervention for an Hourly Activity Habit Among Caregivers for Persons With AD/ADRD

The primary outcome will be a binary indicator of habit formation. A null hypothesis rate of 30 percent will be used. There will be a comparison of the achieved proportion of habitual walking versus this null level, using a 1-sample binomial test with a 2-sided alpha at 5 percent. For the purposes of this current analysis, it is assumed that 50 percent of the sample will achieve habitual hourly walking following the BCT intervention to encourage habit formation. Rate of habit formation will be summarized using the observed proportion along with a 95 percent confidence interval.

Examining whether an hourly walking habit formation will be associated with positive changes in cognitive automaticity using Fisher's exact test (5%, 2-sided). Specifically, for each participant, the difference between average automaticity during the last 2 weeks of intervention and average baseline automaticity will be calculated; a positive change is defined as a difference of greater than zero. The rate of habit formation will be compared between the group of participants whose automaticity increased and the participants whose automaticity did not using a Fisher's exact test. Finally, logistic regression will be utilized to assess the effects of automaticity on development of a daily walking habit, with adjustment for other factors, such caregiver demographic characteristics and factors related to caregiving.

Longitudinal associations between the intervention, automaticity, and habitual walking over time will be examined using univariate logistic regression models. These models will provide preliminary estimates of how automaticity change at a given week will impact habit formation, thus informing how the timing of automaticity change will impact habit. Further, weekly automaticity changes will be explored together in a multivariate Bayesian logistic regression model, which will be trained using iPIPE.238

To examine the heterogeneity of treatment effects for habit formation and on changes in automaticity, analyses of HTEs across participants will be conducted. This will involve examining the heterogeneity in time to achieving habitual hourly walking due to the BCT intervention.