Digital intervention engagement mediates the relationship between intrapersonal measures and pre-exposure prophylaxis adherence: a secondary analysis of a randomized controlled trial of sexual orientation and gender minority youth on pre-exposure prophylaxis (Preprint)

Abstract

BACKGROUND Improving adherence to Pre-Exposure Prophylaxis (PrEP) via digital health interventions (DHIs) for young sexual and gender minority men who have sex with men (YSGMMSM) is promising for reducing HIV burden among YSGMMSM. Measuring and achieving effective engagement (engagement sufficient to solicit PrEP adherence) in YSGMMSM is challenging. OBJECTIVE The present secondary analysis of the P3 (Prepared, Protected, empowered: a digital PrEP adherence intervention) randomized controlled trial (RCT) utilized causal mediation to quantify whether and to what extent intrapersonal behavioral, mental health, and sociodemographic measures were related to effective engagement for PrEP adherence in YSGMMSM. METHODS Of 264 YSGMMSM participants aged 16-24 in the primary RCT, 140 participants were eligible for the present secondary analysis (retained at follow up, received DHI condition in primary RCT, complete trial data). Participants earned US currency for daily usage of P3 and lost US currency for non-usage. Dollars accrued at 3-month follow-up was used to measure engagement. PrEP non-adherence was measured via blood serum levels consistent with ≤4 doses weekly at 3-month follow-up. Logistic regression was used to estimate the total effect of baseline intrapersonal measures on PrEP non-adherence, represented as non-adherence odds ratios (NAR) with a null value of 1. The total NAR for each intrapersonal measure was decomposed into direct and indirect effects. Direct effects represent relationships between intrapersonal measures and PrEP non-adherence controlling for engagement with P3. Indirect effects represent relationships between intrapersonal measures and PrEP non-adherence operating through P3 engagement. RESULTS For every $1 earned above the mean ($96), participants had 2% (NAR=0.98, 95% CI=0.97,0.99) lower odds of PrEP non-adherence. Frequently using phone apps to track health information was associated with a 71% (NAR=0.29, 95% CI=0.06,0.96) lower odds of PrEP non-adherence. This was overwhelmingly a direct effect, not mediated by engagement, with a percent mediated (PM) of 1%. Non-Hispanic White participants had 83% lower odds of PrEP non-adherence (NAR=0.17, 95% CI=0.05,0.48) and was a direct effect (PM=4%). Participants with depressive symptoms and anxious symptoms had 3.4 (NAR=3.42, 95% CI=0.95,12.00) and 3.5 (NAR=3.51, 95% CI=1.06,11.55) higher odds of PrEP nonadherence, respectively. Anxious symptoms largely operated through P3 engagement (PM=51%). CONCLUSIONS P3 engagement (dollars accrued) was strongly related to lower odds of PrEP non-adherence. Intrapersonal measures operating through P3 engagement (indirect effect, e.g., anxious symptoms) suggest possible pathways to improve PrEP adherence DHI efficacy in YSGMMSM via effective engagement. Conversely, the direct effects observed in the present study may reflect existing structural disparity (e.g., race/ethnicity) or behavioral dispositions towards technology (e.g., tracking health via phone apps). Evaluating effective engagement in DHIs with causal mediation approaches provides a clarifying and mechanistic view of how DHIs impact health behavior.