{
  "abstract": "Background\n\nA central concern in ecological momentary assessment (EMA) research is whether repeated self-report alters the reporting process itself. In most EMA domains, longitudinal stability of reporting is assumed but rarely tested.Objective\n\nThis study leveraged concurrent accelerometry as a temporal anchor to evaluate (1) whether self-reported physical activity (PA) and sedentary behavior (SB) exhibited temporal shifts across a 7-day monitoring period and (2) whether this temporal shift differed across near-momentary (5-min reporting period) and coverage-based (120-min recall period) EMA protocols.Methods\n\nWe conducted a secondary analysis of 315 US adults recruited from the Understanding America Study panel between January and July 2023 for the current study. Participants were monitored in their natural environments for 7 days via 2 measurement methods: continuous thigh-worn activPAL4 accelerometry and 5 daily smartphone EMA prompts assessing PA and SB. Reporting reactivity was defined as divergence in the temporal trajectories of EMA-reported behavior relative to accelerometry. Multilevel models with random intercepts and slopes tested whether linear and quadratic study day effects differed across the 2 methods (method × study day interactions). Protocol differences were examined using multivariable method × protocol × study day interactions, comparing coverage-based and near-momentary EMA designs.Results\n\nIn the coverage-based protocol, EMA-reported PA and SB exhibited temporal trajectories that diverged significantly from concurrent accelerometry (SB linear divergence: b=1.40, 95% CI 0.20-2.61, P=.02; PA linear divergence: b=-1.91, 95% CI -2.93 to -0.90, P<.001; and PA quadratic divergence: b=0.28, 95% CI 0.12-0.44, P<.001). No evidence of such divergence was found in the near-momentary protocol. The divergence in reporting trajectories differed significantly between the 2 protocols (SB linear 3-way interaction: b=-2.58, P=.02; PA linear 3-way interaction: b=1.86, P=.04).Conclusions\n\nReporting reactivity in EMA appears protocol-dependent. The coverage-based protocol was associated with modest reporting reactivity, which challenges the common assumption of reporting invariance in EMA and underscores the importance of considering protocol design when interpreting within-person change.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "name": "Meynard John L Toledo",
      "orcid": "0000-0003-0215-003X"
    },
    {
      "name": "Stefan Schneider",
      "orcid": "0000-0002-4562-0524"
    },
    {
      "name": "Joshua Smyth",
      "orcid": "0000-0002-0904-5390"
    },
    {
      "name": "Doerte Junghaenel",
      "orcid": "0000-0002-7733-571X"
    },
    {
      "name": "Arthur Stone",
      "orcid": "0000-0001-7490-1758"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2ryhtxxcwe859.bib",
  "cited_by": 0,
  "doi": "10.2196/99953",
  "fulltext_url": "https://www.jmir.org/2026/1/e99953",
  "id": "2ryhtxxcwe859",
  "issns": [
    "1438-8871",
    "1439-4456"
  ],
  "landing_url": "https://doi.org/10.2196/99953",
  "language": "en",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "heading",
      "Development and Evaluation of Research Methods, Instruments and Tools"
    ],
    [
      "heading",
      "Ecological Momentary Assessment (EMA)"
    ],
    [
      "heading",
      "Electronic/Mobile Data Capture, Internet-based Survey & Research Methodology"
    ],
    [
      "heading",
      "Evaluation and Research Methodology for mHealth"
    ],
    [
      "heading",
      "Fitness Trackers and Smart Pedometers/Accelerometers"
    ],
    [
      "heading",
      "Original Paper"
    ],
    [
      "heading",
      "mHealth for Data Collection and Research"
    ],
    [
      "lcc",
      "R858-859.7"
    ],
    [
      "lcc",
      "RA1-1270"
    ],
    [
      "openalex",
      "3205|Mental Health Research Topics"
    ]
  ],
  "openalex": "W7224345445",
  "pdf_url": "https://europepmc.org/articles/PMC13717333?pdf=render",
  "pmcid": "PMC13717333",
  "pmid": "42954100",
  "published": "2026-10-23",
  "publisher": "JMIR Publications",
  "ris": "https://research.draconitic.com/paper/2ryhtxxcwe859.ris",
  "sources": [
    {
      "first_seen": "2026-10-31T14:22:50Z",
      "native_id": "06ea570507d34b3c92fb8537f13029bf",
      "source": "doaj",
      "url": "https://doi.org/10.2196/99953"
    },
    {
      "first_seen": "2026-11-01T00:20:36Z",
      "native_id": "MED:42954100",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42954100"
    },
    {
      "first_seen": "2026-11-02T12:21:40Z",
      "native_id": "PMC13717333",
      "source": "pmc",
      "url": "https://doi.org/10.2196/99953"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "lcc:RA1-1270",
      "subfield": "epidemiology-public-health"
    }
  ],
  "title": "Temporal Stability of Repeated Self-Reported vs Device-Measured Behavior: Observational Study Using Ecological Momentary Assessment",
  "title_text": "Temporal Stability of Repeated Self-Reported vs Device-Measured Behavior: Observational Study Using Ecological Momentary Assessment",
  "type": "peer-reviewed",
  "updated_at": "2026-11-02T12:21:40Z",
  "url": "https://research.draconitic.com/paper/2ryhtxxcwe859",
  "venue": "Journal of Medical Internet Research",
  "versions": []
}