Support Strategies to Enhance Adherence to a Prescription Digital Therapeutic for Erectile Dysfunction: Retrospective Quasi-Experimental Cohort Study.

backgroundSustained engagement is a central challenge for digital therapeutics. In routine operations, inactivity-triggered supports (eg, SMS reminders and telephone follow-up) are used to nudge patients back after lapses, but evidence in digital erectile dysfunction (ED) therapy is limited.

objectiveThis study aims to evaluate whether low-threshold support in the form of SMS reminders and structured telephone outreach, both triggered after 7 or more days of inactivity, improves engagement and patient-centered outcomes in a certified German digital health application (Digitale Gesundheitsanwendung [DiGA]) for ED.

methodsIn a pragmatic, calendar-time (rotating-week) quasi-experimental allocation, 470 men with physician-diagnosed ED entered 1 of 3 groups: control (no additional support), SMS (automated reminders), or call (structured telephone contact). Analyses were conducted as assigned. The primary end point was active weeks (number of weeks with ≥1 completed session) during the 12-week study period, derived from app logs with built-in completion rules. A prespecified mechanistic end point captured any reactivation after an inactive week (yes or no). Secondary end points included Clinical Global Impression-Improvement (CGI-I), week-12 5-item International Index of Erectile Function (IIEF-5), intention to continue therapy, and documented continuation ("conversion") within 3 months. Covariate-adjusted models included age, BMI, smoking, and baseline pharmacotherapy; calendar-week sensitivity was planned.

resultsParticipants completed a mean of 6.34 (SD 4.44) active weeks. Unadjusted means favored both support groups (control: 5.79; call: 6.57; SMS: 6.80); the prespecified SMS-vs-control contrast was nominally significant (P=.049, small effect). In covariate-adjusted models, planned pairwise contrasts were not significant. In a calendar-adjusted sensitivity model, the omnibus group term reached significance, but adjusted pairwise contrasts remained nonsignificant; stricter adherence definitions led to the same overall inference. By contrast, any reactivation after inactivity was more common in the intervention groups than in the control group (omnibus chi-square test P=.008), consistent with the intended mechanism of breaking inactivity spells. The call group showed a higher intention to continue therapy (49% vs 38% in the control arm; P=.04); conversion did not differ. CGI-I and IIEF-5 showed no arm-wise differences over 12 weeks; follow-up availability was limited in routine care.

conclusionsInactivity-triggered supports in a real-world ED DiGA reactivated use after lapses, and telephone outreach increased motivation to continue, while effects on weekly dose were small and not significant after adjustment, and clinical outcomes did not differ over 12 weeks. Programs may consider a stepped approach (SMS first-line nudge and call as escalation) and target system bottlenecks that decouple motivation from realized continuation. Further work should test longer-term outcomes, targeting, and generalizability.