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      A Catalog of Rules, Variables, and Definitions Applied to Accelerometer Data in the National Health and Nutrition Examination Survey, 2003–2006

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      , PhD , , PhD, , PhD
      Preventing Chronic Disease
      Centers for Disease Control and Prevention

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          Abstract

          Introduction

          The National Health and Nutrition Examination Survey (NHANES) included accelerometry in the 2003–2006 data collection cycles. Researchers have used these data since their release in 2007, but the data have not been consistently treated, examined, or reported. The objective of this study was to aggregate data from studies using NHANES accelerometry data and to catalogue study decision rules, derived variables, and cut point definitions to facilitate a more uniform approach to these data.

          Methods

          We conducted a PubMed search of English-language articles published (or indicated as forthcoming) from January 2007 through December 2011. Our initial search yielded 74 articles, plus 1 article that was not indexed in PubMed. After excluding 21 articles, we extracted and tabulated details on 54 studies to permit comparison among studies.

          Results

          The 54 articles represented various descriptive, methodological, and inferential analyses. Although some decision rules for treating data (eg, criteria for minimal wear-time) were consistently applied, cut point definitions used for accelerometer-derived variables (eg, time spent in various intensities of physical activity) were especially diverse.

          Conclusion

          Unique research questions may require equally unique analytical approaches; some inconsistency in approaches must be tolerated if scientific discovery is to be encouraged. This catalog provides a starting point for researchers to consider relevant and/or comparable accelerometer decision rules, derived variables, and cut point definitions for their own research questions.

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          Most cited references45

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          Physical activity in U.S.: adults compliance with the Physical Activity Guidelines for Americans.

          To date, no study has objectively measured physical activity levels among U.S. adults according to the 2008 Physical Activity Guidelines for Americans (PAGA). The purpose of this study was to assess self-reported and objectively measured physical activity among U.S. adults according to the PAGA. Using data from the NHANES 2005-2006, the PAGA were assessed using three physical activity calculations: moderate plus vigorous physical activity ≥150 minutes/week (MVPA); moderate plus two instances of vigorous physical activity ≥150 minutes/week (M2VPA); and time spent above 3 METs ≥500 MET-minutes/week (METPA). Self-reported physical activity included leisure, transportation, and household activities. Objective activity was measured using Actigraph accelerometers that were worn for 7 consecutive days. Analyses were conducted in 2009-2010. U.S. adults reported 324.5 ± 18.6 minutes/week (M ± SE) of moderate physical activity and 73.6 ± 3.9 minutes/week of vigorous physical activity, although accelerometry estimates were 45.1 ± 4.6 minutes/week of moderate physical activity and 18.6 ± 6.6 minutes/week of vigorous physical activity. The proportion of adults meeting the PAGA according to M2VPA was 62.0% for self-report and 9.6% for accelerometry. According to the NHANES 2005-2006, fewer than 10% of U.S. adults met the PAGA according to accelerometry. However, physical activity estimates vary substantially depending on whether self-reported or measured via accelerometer. Copyright © 2011 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.
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            Accelerometer data reduction: a comparison of four reduction algorithms on select outcome variables.

            Accelerometers are recognized as a valid and objective tool to assess free-living physical activity. Despite the widespread use of accelerometers, there is no standardized way to process and summarize data from them, which limits our ability to compare results across studies. This paper a) reviews decision rules researchers have used in the past, b) compares the impact of using different decision rules on a common data set, and c) identifies issues to consider for accelerometer data reduction. The methods sections of studies published in 2003 and 2004 were reviewed to determine what decision rules previous researchers have used to identify wearing period, minimal wear requirement for a valid day, spurious data, number of days used to calculate the outcome variables, and extract bouts of moderate to vigorous physical activity (MVPA). For this study, four data reduction algorithms that employ different decision rules were used to analyze the same data set. The review showed that among studies that reported their decision rules, much variability was observed. Overall, the analyses suggested that using different algorithms impacted several important outcome variables. The most stringent algorithm yielded significantly lower wearing time, the lowest activity counts per minute and counts per day, and fewer minutes of MVPA per day. An exploratory sensitivity analysis revealed that the most stringent inclusion criterion had an impact on sample size and wearing time, which in turn affected many outcome variables. These findings suggest that the decision rules employed to process accelerometer data have a significant impact on important outcome variables. Until guidelines are developed, it will remain difficult to compare findings across studies.
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              Physical activity in US youth: effect of race/ethnicity, age, gender, and weight status.

              To describe physical activity (PA) levels by race/ethnicity, age, gender, and weight status in a representative sample of US youth. Cross-sectional data from the 2003-2004 and 2005-2006 National Health and Nutrition Examination Survey were combined and analyzed. Youth aged 6-19 yr with at least four 10-h days of PA measured by accelerometry were included (n = 3106). Outcomes included mean counts per minute and minutes spent in moderate-to-vigorous PA (MVPA). Among the groups, the 6- to 11-yr-olds spent more time (88 min·d) in MVPA than the 12- to 15-yr-olds (33 min·d) and 16- to 19-yr-olds (26 min·d; P 0.050). There was a significant three-way age-body mass index-race/ethnicity interaction for mean minutes per day in MVPA (P < 0.001). Adjustment for total energy intake did not qualitatively alter these results. Females and older youth were the least active groups. Obese youth were generally less active, but this did not hold uniformly across race/ethnic groups. Cultural or biological factors could moderate the association between PA and obesity in youth.
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                Author and article information

                Journal
                Prev Chronic Dis
                Prev Chronic Dis
                PCD
                Preventing Chronic Disease
                Centers for Disease Control and Prevention
                1545-1151
                2012
                14 June 2012
                : 9
                : E113
                Affiliations
                [1]Author Affiliations: Sarah M. Camhi, University of Massachusetts, Boston, Massachusetts; Richard P. Troiano, National Cancer Institute, Bethesda, Maryland.
                Author notes
                Corresponding Author: Catrine Tudor-Locke, PhD, Director, Walking Behavior Laboratory, Pennington Biomedical Research Center, Baton Rouge, LA 70808. Telephone: 225-763-2974. E-mail: Tudor-Locke@ 123456pbrc.edu .
                Article
                11_0332
                10.5888/pcd9.110332
                3457743
                22698174
                3c6df1f3-d346-4361-bb0a-cfe7086df119
                History
                Categories
                Systematic Review
                Peer Reviewed

                Health & Social care
                Health & Social care

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