JMIR Publications

ABSTRACT

Background:

Longitudinal studies of many health behaviors often rely on infrequent self-report assessments. The measurement of psychoactive substance use among youth is expected to improve with more frequent mobile assessment, which can reduce recall bias. Researchers have used mobile devices for longitudinal research, but studies that last years and assess youth continuously at a fine-grained temporal level (e.g., weekly) are rare. A tailored mobile app (mNCANDA) and brief assessment protocol were designed specifically to provide a feasible platform to elicit responses to health behavior assessments in longitudinal studies.

Objective:

This study aimed to determine if an acceptable mobile app system could provide repeatable and valid assessment of health behaviors for youth in different developmental stages over extended follow-up.

Methods:

Participants were recruited (N =583, ages 17-28 years) from a larger longitudinal study of neurodevelopment. Participants used the mNCANDA mobile app to register reports of their behaviors for up to 18 months. Response rates as a function of time being measured with mNCANDA, and participant age were modeled using generalized estimating equations to evaluate response rate stability and age effects. mNCANDA-captured substance use reports were compared to responses from standardized interviews to assess concurrent validity. Reactivity was assessed by evaluating patterns of change in substance use after participants initiated weekly reports via mNCANDA. All participants were invited to complete a one-time questionnaire that assessed attitudes and perceptions related to mNCANDA. Qualitative interviews were conducted with a subset of participants who used the app for at least 1-month to obtain feedback on user experience, user-derived explanations of some quantitative results, and suggestions for system improvements.

Results:

mNCANDA protocol adherence was high (Mresponse rate = 82%, SD=27%) and stable over time, across age. Median time to complete each assessment was 51 seconds (Mresponse time= 1.14 min, SD= 1.03 min). Comparisons between mNCANDA and interview self-report on recent (prior 30 days) alcohol and cannabis use days demonstrate close agreement (e.g., within 1 day of reported use) for most observations. Models used to identify reactivity failed to detect changes in substance use patterns subsequent to enrolling in mNCANDA app assessments (P’s > .39). The majority (84%) of participants across the age range reported finding the mNCANDA system acceptable. Participants provided recommendations for improving the system (e.g., tailoring signaling times).

Conclusions:

mNCANDA provides a feasible, multi-year, continuous fine-grained (e.g., weekly) assessment of health behaviors designed to minimize respondent burden and provides acceptable regimes for long-term self-report of health behaviors. Fine-grained characterization of variability in behaviors over relatively long periods (e.g., up to 18 months) may, through the use of mNCANDA, improve our understanding of the relationship between substance use exposure and neurocognitive development.