Conclusions
EMA
This study is one of the first to experimentally evaluate the effect of incentives and schedule length on EMA response rates. It is also the first study to consider factors related to response in the context of an ongoing prospective cohort study administering repeated bursts of EMA over a 2-year period. By embedding RCTs within an ongoing study, it was possible to rapidly implement and evaluate whether altering the implementation strategy, incentives, or schedule length would increase the response rate. Our study therefore contributes to a small but growing body of literature on how to implement EMA. This knowledge is essential for collecting high-quality EMA data, which has a flow-on effect to the quality of conclusions that can be drawn from these data.This study was funded by the Health Promotion Board of the Singapore Government. The funder had no role in the analysis, interpretation of the data, or the decision to submit the manuscript for publication.Reporting of these nested trials followed the CONSORT (Consolidated Standards of Reporting Trials) extension for the reporting of randomized controlled trials conducted using cohorts and routinely collected data (Authors' Contributions: KC, RMvD, and FM-R secured study funding. All the authors made substantial contributions to the study design. AL and XHC were responsible for data acquisition. CMJLG, RMvD, CST, FM-R, and SME planned the data analysis. CMJLG performed the data analysis with input from CST and SME. SME drafted the manuscript. All authors critically reviewed the manuscript and approved the final version.Conflicts of Interest: SME, CMJLG, XHC, RMvD, CST, and FM-R declare no competing interests. AL, JC, DK, and KC declare no competing financial interests, but they are current employees at the Singapore Government Health Promotion Board.Overview of the 14- and 7-day ecological momentary assessment schedules including number of questions sent per ecological momentary assessment survey.Constructs assessed via Ecological Momentary Assessment surveys—example questions and response options.Per day response rate for each burst of Ecological Momentary Assessment surveys.CONSORT-ROUTINE (Consolidated Standards of Reporting Trials extension for the reporting of randomised controlled trials conducted using cohorts and routinely collected data) checklist.CONSORT-EHEALTH checklist.