Triggered Nurse Support for Sustained App Use Among Older Adults with Chronic Conditions: A Pragmatic Randomised Trial

Background & Objective:​ We examine whether nurse support triggered by objectively detected difficulty — rather than support delivered on a schedule or on request — increases sustained meaningful use of a health application over 12 weeks among older adults with chronic conditions. Study Design:​ A two-stage, multicentre, parallel-group, pragmatic randomised controlled trial with 1:1 allocation and blinded outcome assessment, conducted at 8 sites in southwest China (two tertiary hospitals, two secondary hospitals, four residential care facilities). Stage 1 was an independent 24-participant pilot used solely to calibrate parameters; its data are not included in the main analysis. Randomisation was stratified by site and by baseline performance stratum. Participants & Sample Size:​ 452 participants (226 per arm). Eligible participants were adults aged ≥60 years with at least one chronic condition requiring ongoing self-management, who owned a smartphone they could unlock unaided and gave written informed consent. Exclusions were severe cognitive impairment precluding consent, sensory impairment uncorrectable by the application's accessibility settings, terminal illness, and established use of a comparable application. Assuming a between-group difference of 0.10 in WMUP with SD 0.32, 226 per arm provides 85% power at a two-sided α of 0.05, allowing for 20% loss to follow-up. Intervention:​ Both arms received the same investigator-built health application and identical onboarding. In the intervention arm, five locked rules (R1–R5) applied to server-log behaviour triggered one of three responses: an automated in-app prompt (L1), a nurse contact (L2), or clinical escalation (L3), subject to 24-hour merging, 48-hour and 168-hour cooldowns, and dose ceilings (L1 ≤2 per week; L2 ≤6 across 12 weeks). In the control arm the same rules were computed and recorded as not actionable and generated no response. Primary Outcome:​ The weekly meaningful use proportion (WMUP) over weeks 1–12, analysed by intention-to-treat and adjusted for site, baseline performance stratum and age band (60–74 versus ≥75). WMUP is the number of qualifying weeks divided by the number of evaluable weeks contributed by that participant; a qualifying week contained at least two meaningful-use days. Meaningful use was determined programmatically from server logs and excluded opening the application, background synchronisation, brief browsing and any nurse-performed action; days on which a technical failure prevented use were not evaluable and were excluded. The pre-specified sensitivity analysis counted all 12 weeks for every randomised participant, treating weeks after withdrawal as not qualifying. Registration Status Note:​ This is not a clinical trial registration. The trial was not registered in a clinical trial registry (that is, in a WHO ICTRP primary registry or in ClinicalTrials.gov), and this item is not submitted as a substitute for such registration. It was created after data collection had ended. Its purpose is to place the pre-specified protocol, the primary outcome definition and the statistical analysis plan on public record with a time stamp, so that the design, the outcome definitions and the analysis plan can be inspected against the dates they carry. All documents were signed and finalised before database freeze and unblinding; the analysis plan carries a dated change-control record (C-01 to C-04), every entry of which predates unblinding. No amendment altered the primary outcome definition, the analysis set or the sample size. This deposit contains no study results.