BACKGROUND: To the best of our knowledge, this is the first study to examine the relationship of rest-activity rhythm with survival in older adults with lung cancer and to consider variations in rest-activity rhythm over time. OBJECTIVE: The aim of this study was to explore the relationship between rest-activity rhythm variations and survival in 33 older adults with lung cancer by considering rest-activity rhythm as a time-dependent covariate over time. METHODS: In this prospective study with 5 repeated measurements, patients' rest-activity rhythm over 3 days was measured using actigraphy. The rest-activity rhythm was represented using the dichotomy index I (in-bed activity) < O (out-of-bed activity). The median I < O was used as the cutoff point, with an I < O of greater than or equal to 85.59% and less than 85.59% indicating robust and disrupted rest-activity rhythms, respectively. Data were analyzed using the Cox regression model with time-dependent repeated measurements of a covariate. RESULTS: In the time-dependent multivariate Cox model, a disrupted rest-activity rhythm was independently associated with a higher risk of death than was a robust rest-activity rhythm (hazard ratio, 16.05; P = .009). CONCLUSION: A time-varying rest-activity rhythm is incrementally associated with mortality in older adults with lung cancer and represents a rigorous and independent prognostic factor for their survival. IMPLICATIONS FOR PRACTICE: Clinicians may need to pay more attention to the rest-activity rhythms of older adults with lung cancer during disease progression. Future studies should account for the variation in rest-activity rhythm over time.
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