Daily Reminders Increase Adherence to an Electronic Headache Diary (DMKG-App): Retrospective Longitudinal Cohort Study.

BACKGROUND: The use of electronic headache diaries via smartphone apps has several advantages over paper and pencil diaries. Still, adherence is not always satisfactory. One potential strategy to improve adherence is the implementation of daily reminders, but their effect remains uncertain. OBJECTIVE: The DMKG-App (the headache diary app of the German Migraine and Headache Society, DMKG) sends daily reminders to encourage user adherence. Due to a technical problem, reminders failed for a 14-day period in early 2023. This provided a unique opportunity to evaluate the effect of daily reminders on adherence to the headache diary in the form of a retrospective longitudinal observational cohort study. METHODS: The failure period was compared to 14-day prefailure and postfailure periods and to corresponding periods of the previous year. We evaluated effects on the number of daily entries, delay to make the daily entry, and attrition rate, using ANOVA and logistic regression (α<.05). The effect of age, gender, headache frequency, and previous adherence was investigated using interaction analysis. RESULTS: The DMKG-App had 4236 active users before reminders failed (females 81.6%, 95% CI 80.5-82.8), age 39.8 (95% CI 39.4-40.2) years. During the failure period, the number of daily entries fell by 11.0% (95% CI 9.2-12.8). More specifically, entries per 14-day period significantly declined from 10.2 (95% CI 10.1-10.3) prefailure to 9.1 (95% CI 9.0-9.2) during the failure period, followed by a rise to 10.2 (95% CI 10.1-10.3) during the postfailure period (F2,11498=79.2; P<.001). The delay to make the daily entry increased by 46.3% (95% CI 45.8-46.8), from 1.90 (95% CI 1.89-1.90) days prefailure to 2.78 (95% CI 2.77-2.79) days during failure, and returned to 1.85 (95% CI 1.84-1.86) days postfailure (F2,39=155.4; P<.001). In addition, there was a significant rise in attrition rate by 32.2% (95% CI 8.1-61.7) (from 4.0%, 95% CI 3.4-4.6, in the prefailure period to 5.2%, 95% CI 4.6-5.9, in the failure period, returning to 3.9%, 95% CI 3.4-4.5, in the postfailure period, z=3.10; P=.002). Interaction analysis revealed that the effect of reminder failure was larger in males than in females (regarding entry delay), in persons with lower compared to higher headache frequencies (regarding number of daily entries and entry delay), and in persons with higher vs lower previous adherence rates (regarding number of daily entries, entry delay, and attrition). There was no interaction between age and reminder failure. CONCLUSIONS: This is the first study investigating the effect of daily reminders in a digital headache diary app. Results suggest that reminders are an effective means to improve adherence. Males, persons with low headache frequencies, and those with high adherence during the presence of reminders seem to benefit most. These results are important additions to our knowledge on compliance with digital health apps.