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Accelerometer data reduction in adolescents: effects on sample retention and bias.

Mette Toftager1, Peter Lund Kristensen, Melody Oliver

  • 1Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense, Denmark. mtoftager@health.sdu.dk.

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Stricter accelerometer data criteria exclude more overweight and older adolescents, potentially biasing physical activity (PA) and sedentary behavior results. Careful selection of data reduction methods is crucial for accurate adolescent PA assessment.

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Area of Science:

  • Pediatric Exercise Science
  • Biomedical Data Analysis
  • Public Health Research

Background:

  • Accelerometry is a reliable method for assessing physical activity (PA) in youth.
  • Inconsistent data reduction criteria for accelerometry can affect study outcomes.
  • The impact of participant exclusion based on these criteria is not well understood.

Purpose of the Study:

  • To investigate how different accelerometer data reduction criteria affect the characteristics of adolescents included in analyses.
  • To assess the influence of varying data reduction settings on sample retention and physical activity (PA) outcomes.
  • To identify potential biases introduced by specific data reduction criteria in adolescent populations.

Main Methods:

  • Utilized accelerometer data, anthropometric measures, and survey data from 1348 adolescents (aged 11-14 years).
  • Analyzed accelerometer data using varied criteria for valid days, daily wear time, and non-wear time.
  • Employed ordinal logistic regression and multilevel mixed-effect linear regression to analyze subgroup impacts.

Main Results:

  • Stricter criteria (more valid days, longer wear time, shorter non-wear definitions) reduced participant retention.
  • Non-wear time definitions significantly influenced which adolescents were retained.
  • Adolescents with higher BMI and older age were more likely to be excluded with shorter non-wear time definitions.

Conclusions:

  • Minor variations in accelerometer data reduction criteria can significantly alter sample size and PA/sedentary outcomes.
  • Using short non-wear time definitions risks excluding a disproportionate number of overweight and older adolescents, introducing bias.
  • Standardizing accelerometer data reduction criteria is essential for reliable and unbiased research in adolescent populations.