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Quantifying the time-varying association between objectively measured physical activity and mortality in US older adults over a 12-year follow-up period: the NHANES 2003–2006 study
  1. Neha Agarwala1,
  2. Vadim Zipunnikov2,
  3. Ciprian Crainiceanu2,
  4. Andrew Leroux3
  1. 1Department of Mathematics and Statistics, University of Maryland Baltimore County, Baltimore, Maryland, USA
  2. 2Department of Biostatistics, Johns Hopkins University, Baltimore, Maryland, USA
  3. 3Department of Biostatistics and Informatics, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
  1. Correspondence to Dr Neha Agarwala, Department of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, USA; ag.neha2010{at}gmail.com

Abstract

Objectively measuring physical activity (PA) has consistently shown an association with reduced all-cause mortality risk in cross-sectional studies. However, the strength of this association may change over time. We quantify the time-varying, covariate-adjusted association between the total volume of PA and all-cause mortality over a 12-year follow-up period using Cox regression with a time varying effect of population-referenced quantile total activity count adjusted for traditional risk factors. Analyses focus on participants 50–84 years old with adequate accelerometer wear time and without missing covariates. The findings suggest that (1) the use of baseline PA in Cox models with long follow-up periods may be inappropriate without time-varying effects and (2) the use of accelerometry derived volume of PA in risk score calculations may be most appropriate for short-term to medium-term risk scores.

  • Physical Fitness
  • Health Planning
  • Methods
  • Public health
  • Behavioral Disciplines and Activities

Data availability statement

Data are available in a public, open access repository. NHANES data are publicly available.

https://doi.org/10.1136/bmjebm-2023-112303

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    Data availability statement

    Data are available in a public, open access repository. NHANES data are publicly available.

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    Footnotes

    • Contributors Study concept and design: VZ, AL and CC; Acquisition of the data: AL and NA; Analysis and interpretation of the data: AL and NA; Preparation of manuscript: AL, NA, CC and VZ. Guarantor: AL.

    • Funding This work was supported by NIH/NINDS grant R01 grant NS060910 Statistical Methods for Multilevel Multivariate Functional Studies.

    • Disclaimer The funding agencies that supported the research had no role in the development of these analyses or the preparation of the manuscript.

    • Competing interests CC is consulting with Bayer and Johnson and Johnson on methods development for wearable devices in clinical trials. The details of the contracts are disclosed through the Johns Hopkins University eDisclose system and have no direct or apparent relationship with this manuscript.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.