Principal Findings
OFD, contextual behaviors
REGRESSION, EVENTS, EVENT, EMA
This pilot study tested the feasibility and acceptability of using EMA to capture OFD events and contextual behaviors in young people aged 16 to 35 years. Compliance rates, as an indicator of feasibility, to signal-contingent and event-contingent protocols were similar at 72% and 73%, respectively, in adults. However, participants in the event-contingent group were more likely to have captured an OFD event during the study period. The EMA protocols for both groups were acceptable; however, most participants agreed that the study could be improved by an app that was easier to navigate. Contextual data revealed that OFD orders consisted largely of unhealthy foods. These orders were commonly placed for evening meals, typically after 6 PM, were mostly for a single person, and were ordered at home. Moreover, the orders often originated from an outlet within a 15- to 30-minute walking distance. Analyses showed that there was a significant association between age, number of dependents, and number of OFD events. These formative findings warrant further investigation with refinement of the EMA methodology to increase acceptability and improve the OFD data captured from participants.High compliance rates indicated a feasible and acceptable EMA protocol for the study population and events captured. In the guidelines proposed by Stone and Shiffman [Participants who were assigned to the event-contingent sampling approach were 3 times more likely to have had an OFD event captured during the study compared with the signal-contingent group. This indicates that event-contingent sampling appeared to be the better approach to capturing OFD events. It is likely that event-contingent sampling was more appropriate because of OFD being a specific and sporadic event that, among study participants, varied in the frequency of use. Thus, unprompted records of any instance of OFD over the 1-week monitoring period were more effective than answering prompts delivered on 3 random sampling days. However, an additional end-of-day reminder proved to be critical for the event-contingent group as almost one-third (22/79, 28%) of the OFD orders were captured through this reminder, which otherwise would have been forgotten.Another possible key factor affecting participants’ experience of the EMA study and compliance was the perceived ease of use of the mobile app used to capture data. Many participants found that the EMA app was difficult to navigate and not user friendly, which may have negatively affected their experience of this study. Another EMA study also found participants commenting on the “difficult and bothersome” nature of EMA apps, although this was specific to the Visual Analog Slider used for one of the momentary assessments [This study revealed that orders were commonly placed for evening meals, typically after 6 PM, were mostly for a single person, and were ordered at home. Moreover, the orders often originated from an outlet within a 15- to 30-minute walking distance. According to physical activity research, a 1-km distance typically reflects a 15- to 20-minute walk for an average adult [The results from a zero-inflated negative binomial regression model showed that dependents were positively associated with the number of OFD events. This finding is consistent with a previous study conducted by Keeble et al [Convenience prevailed as the selected reason for an OFD order (46/124, 37.1%), whereas “being busy” accounted for 12.1% (15/124) of the orders. Price promotions were also used in approximately one-third of all recorded events. These findings align with a qualitative study from the United Kingdom that investigated customer experiences of using OFD services [